Misplaced Pages

#663336

111-563: See text Ug99 is a lineage of wheat stem rust ( Puccinia graminis f. sp. tritici ), which is present in wheat fields in several countries in Africa and the Middle East and is predicted to spread rapidly through these regions and possibly further afield, potentially causing a wheat production disaster that would affect food security worldwide. In 2005 the noted green revolution pioneer Norman Borlaug brought great attention to

222-446: A 2D gel electrophoresis . The Bradford assay is a molecular biology technique which enables the fast, accurate quantitation of protein molecules utilizing the unique properties of a dye called Coomassie Brilliant Blue G-250. Coomassie Blue undergoes a visible color shift from reddish-brown to bright blue upon binding to protein. In its unstable, cationic state, Coomassie Blue has a background wavelength of 465 nm and gives off

333-739: A plasmid ( expression vector ). The plasmid vector usually has at least 3 distinctive features: an origin of replication, a multiple cloning site (MCS), and a selective marker (usually antibiotic resistance ). Additionally, upstream of the MCS are the promoter regions and the transcription start site, which regulate the expression of cloned gene. This plasmid can be inserted into either bacterial or animal cells. Introducing DNA into bacterial cells can be done by transformation via uptake of naked DNA, conjugation via cell-cell contact or by transduction via viral vector. Introducing DNA into eukaryotic cells, such as animal cells, by physical or chemical means

444-482: A bridge from one growing season to another. In other cases the fungus passes between winter wheat and spring wheat, meaning that it has a cereal host all year round. Since the urediniospores are wind dispersed, this can occur over large distances. Note that this cycle consists simply of vegetative propagation – urediniospores infect one wheat plant, leading to the production of more urediniospores that then infect other wheat plants. Puccinia graminis produces all five of

555-569: A common ancestor, but differ in their virulence /avirulence profiles and the countries in which they have been detected. Ug99 is the product of a type of somatic nuclear exchange event which has not been observed in other stem rust races. During this event and thereafter the nuclei have not experienced recombination . Ug99 and its variants differ from other strains of the Black Stem Rust (BSR) pathogen due to their ability to overcome resistance genes in wheat that have been durable against

666-814: A common ancestor. Also known as PTKS . The first Ug99 race to be characterised. Like most Ug99 races, and unlike other stem rust varieties, it is virulent against the Sr gene Sr31 ; also virulent against Sr38 . Avirulent against Sr24 . It was found in Uganda in 1999 , Kenya in 2001 , Ethiopia in 2003 , Sudan and Yemen in 2006 , Iran in 2007 , and Tanzania in 2009 , Eritrea in 2012 , and Rwanda and Egypt in 2014 . First detected in South Africa in 2000 , Zimbabwe 2009 , and Uganda in 2012 . Avirulent on Sr31 . Discovered in Kenya in 2006

777-506: A continuous process of development of new resistant cultivars and failure of those cultivars. This demonstrates the need for continuous improvement. As of 2020 modern molecular and molecular genetics techniques are identifying quantitative trait loci (QTLs), particular cellular structures, and individual R genes more efficiently than ever before. These will be needed given the continuing severe, worldwide threat Ug99 poses. Sr35 confers resistance to all other severe Pgt races and

888-451: A density gradient, which separated the DNA molecules based on their density. The results showed that after one generation of replication in the N medium, the DNA formed a band of intermediate density between that of pure N DNA and pure N DNA. This supported the semiconservative DNA replication proposed by Watson and Crick, where each strand of the parental DNA molecule serves as a template for

999-455: A federal quarantine was established against the sale of stem rust susceptible barberry in those states that were part of the program. A barberry testing program was created to ensure that only those species and varieties of barberry that are immune to stem rust will be grown in the quarantine area. In 1969 two races not detected before in Australia were found and for decades one hypothesis

1110-504: A few other locations in the US, and overall across the US, this race declined 97–98 in favor of other races, and not because of overall Pg decline. As listed by Species Fungorum ; The stem rust fungus attacks the parts of the plant that are above ground. Spores that land on green wheat plants form a pustule that invades the outer layers of the stalk. Infected plants produce fewer tillers and set fewer seed, and in cases of severe infection

1221-424: A group of cultivars known to bear that gene. Pgt contains many races of wheat diseases, including some of the most significant in the world. Ug99 began as a race ( TTKSK ) of Pgt and now has proliferated into a large number of races of its own . The virulent new race, against which most current wheat strains show no resistance, was identified in 1999. The race was named TTKSK (e.g. isolate Ug99), named after

SECTION 10

#1732773022664

1332-526: A host's immune system cannot recognize the bacteria and it kills the host. The other, avirulent, rough strain lacks this polysaccharide capsule and has a dull, rough appearance. Presence or absence of capsule in the strain, is known to be genetically determined. Smooth and rough strains occur in several different type such as S-I, S-II, S-III, etc. and R-I, R-II, R-III, etc. respectively. All this subtypes of S and R bacteria differ with each other in antigen type they produce. The Avery–MacLeod–McCarty experiment

1443-462: A host, John Craigie , a Canadian pathologist, identified the function of the spermogonium in 1927. Due to the useful nature of both barberry and wheat plants, they were eventually brought to North America by European colonists. Barberry was used for many things like making wine and jams from the berries to tool handles from the wood. Ultimately, as they did in Europe, the colonists began to notice

1554-456: A labeled complement of a sequence of interest. The results may be visualized through a variety of ways depending on the label used; however, most result in the revelation of bands representing the sizes of the RNA detected in sample. The intensity of these bands is related to the amount of the target RNA in the samples analyzed. The procedure is commonly used to study when and how much gene expression

1665-518: A mixture of proteins. Western blots can be used to determine the size of isolated proteins, as well as to quantify their expression. In western blotting , proteins are first separated by size, in a thin gel sandwiched between two glass plates in a technique known as SDS-PAGE . The proteins in the gel are then transferred to a polyvinylidene fluoride (PVDF), nitrocellulose, nylon, or other support membrane. This membrane can then be probed with solutions of antibodies . Antibodies that specifically bind to

1776-561: A new virulent race of stem rust was identified against which most current wheat strains show no resistance. The race was named TTKSK (e.g. isolate Ug99 ). An epidemic of stem rust on wheat caused by race TTKSK spread across Africa , Asia and the Middle East , causing major concern due to the large numbers of people dependent on wheat for sustenance, thus threatening global food security . An outbreak of another virulent race of stem rust, TTTTF, took place in Sicily in 2016, suggesting that

1887-428: A receptive hypha of the opposite mating type , leading to the production of a mycelium that is dikaryotic . This is the sexual stage of the life cycle and cross-fertilisation provides an important source of genetic recombination. This dikaryotic mycelium then forms structures called aecia , which produce a type of dikaryotic spores called aeciospores . These have a worty appearance and are formed in chains – unlike

1998-436: A reddish-brown color. When Coomassie Blue binds to protein in an acidic solution, the background wavelength shifts to 595 nm and the dye gives off a bright blue color. Proteins in the assay bind Coomassie blue in about 2 minutes, and the protein-dye complex is stable for about an hour, although it is recommended that absorbance readings are taken within 5 to 20 minutes of reaction initiation. The concentration of protein in

2109-504: A relationship between barberry and stem rust epidemics in wheat. Laws were enacted in many New England colonies, but as the farmers moved west, the problem with stem rust moved with them and began to spread to many areas, creating a devastating epidemic in 1916. It was not until two years later in 1918 that the United States created a program to remove barberry. The program was one that was supported by state and federal entities and

2220-408: A single slide. Each spot has a DNA fragment molecule that is complementary to a single DNA sequence . A variation of this technique allows the gene expression of an organism at a particular stage in development to be qualified ( expression profiling ). In this technique the RNA in a tissue is isolated and converted to labeled complementary DNA (cDNA). This cDNA is then hybridized to the fragments on

2331-501: A small number of spring wheat land races from North America – 23 out of 250 races with adult plant resistance , 27 out of 23,976 SNPs conveying APR, and only 9 races having seedling resistance . This resistance was present without the Ug99 pathogen challenge being present in NA to drive its selection . USDA has studied winter wheat land races where resistance is more probable. In addition to

SECTION 20

#1732773022664

2442-530: A strong and broad pattern of convergent evolution around the plant pathogenic lifestyle . Due to its cyclical nature, there is no true 'start point' for this process. Here, the production of urediniospores is arbitrarily chosen as a start point. Urediniospores are formed in structures called uredinia, which are produced by fungal mycelia on the cereal host 1–2 weeks after infection. The urediniospores are dikaryotic (contain two un-fused, haploid nuclei in one cell) and are formed on individual stalks within

2553-462: A viewpoint on the interdisciplinary relationships between molecular biology and other related fields. While researchers practice techniques specific to molecular biology, it is common to combine these with methods from genetics and biochemistry . Much of molecular biology is quantitative, and recently a significant amount of work has been done using computer science techniques such as bioinformatics and computational biology . Molecular genetics ,

2664-445: A wide area. Towards the end of the cereal host's growing season, the mycelia produce structures called telia. Telia produce a type of spore called teliospores . These black, thick-walled spores are dikaryotic . They are the only form in which Puccinia graminis is able to overwinter independently of a host. Each teliospore undergoes karyogamy (fusion of nuclei) and meiosis to form four haploid spores called basidiospores . This

2775-453: Is heteroecious , requiring two hosts to complete its life cycle – the cereal host and the alternate host . There are many species in Berberis and Mahonia (and their hybrid genus x Mahoberberis ) that are susceptible to stem rust, but the common barberry ( B. vulgaris ) is considered to be the most important alternate host. P. graminis is macrocyclic (exhibits all five of

2886-442: Is a member of the phylum Basidiomycota within the kingdom Fungi . The characteristic rust color on stems and leaves is typical of a general stem rust as well as any variation of this type of fungus. Different from most fungi, the rust variations have five spore stages and alternate between two hosts. Wheat is the primary host, and barberry is the alternate host. The rust is sometimes termed "red rust" or "red dust" owing to

2997-439: Is also a long tradition of studying biomolecules "from the ground up", or molecularly, in biophysics . Molecular cloning is used to isolate and then transfer a DNA sequence of interest into a plasmid vector. This recombinant DNA technology was first developed in the 1960s. In this technique, a DNA sequence coding for a protein of interest is cloned using polymerase chain reaction (PCR), and/or restriction enzymes , into

3108-403: Is an important source of genetic recombination in the life cycle. Basidiospores are thin-walled and colourless. They cannot infect the cereal host, but can infect the alternative host (barberry). They are usually carried to the alternative host by wind. Once basidiospores arrive on a leaf of the alternative host, they germinate to produce a mycelium (which is haploid ) that directly penetrates

3219-439: Is becoming more affordable and used in many different scientific fields. This will drive the development of industries in developing nations and increase accessibility to individual researchers. Likewise, CRISPR-Cas9 gene editing experiments can now be conceived and implemented by individuals for under $ 10,000 in novel organisms, which will drive the development of industrial and medical applications. The following list describes

3330-413: Is called transfection . Several different transfection techniques are available, such as calcium phosphate transfection, electroporation , microinjection and liposome transfection . The plasmid may be integrated into the genome , resulting in a stable transfection, or may remain independent of the genome and expressed temporarily, called a transient transfection. DNA coding for a protein of interest

3441-598: Is caused by the fungus Puccinia graminis , which causes significant disease in cereal crops. Crop species that are affected by the disease include bread wheat , durum wheat , barley and triticale . These diseases have affected cereal farming throughout history. The annual recurrence of stem rust of wheat in North Indian plains was discovered by K.C. Mehta. Since the 1950s, wheat strains bred to be resistant to stem rust have become available. Fungicides effective against stem rust are available as well. In 1999

Ug99 - Misplaced Pages Continue

3552-410: Is centrifuged and the pellet which contains E.coli cells was checked and the supernatant was discarded. The E.coli cells showed radioactive phosphorus, which indicated that the transformed material was DNA not the protein coat. The transformed DNA gets attached to the DNA of E.coli and radioactivity is only seen onto the bacteriophage's DNA. This mutated DNA can be passed to the next generation and

3663-493: Is designated as 'TTKSK' under the North American nomenclature system, was first detected in Uganda in 1998 and first characterised in 1999 (hence the name Ug99) and has since been detected in Kenya , Ethiopia , Eritrea , Sudan , Yemen , Iran , Tanzania , Mozambique , Zimbabwe , South Africa , and Egypt . There are now 15 known races of Ug99. They are all closely related and are believed to have evolved from

3774-433: Is found in a cDNA library . PCR has many variations, like reverse transcription PCR ( RT-PCR ) for amplification of RNA, and, more recently, quantitative PCR which allow for quantitative measurement of DNA or RNA molecules. Gel electrophoresis is a technique which separates molecules by their size using an agarose or polyacrylamide gel. This technique is one of the principal tools of molecular biology. The basic principle

3885-783: Is identified. Similarly, in 2014, a Ug99 race called "Digalu" emerged and devastated the Digalu variety in Ethiopia. JRCQC is a race affecting Durum in Ethiopia . Affects barley. Affects barley. Successfully overwintered in Kansas in 1989/90, and in Texas and Kansas in 1990/91, and so was expected to thereafter be a permanent part of the North American Pg population. Further pathogen adaptation, resulting in widening of

3996-454: Is known as horizontal gene transfer (HGT). This phenomenon is now referred to as genetic transformation. Griffith's experiment addressed the pneumococcus bacteria, which had two different strains, one virulent and smooth and one avirulent and rough. The smooth strain had glistering appearance owing to the presence of a type of specific polysaccharide – a polymer of glucose and glucuronic acid capsule. Due to this polysaccharide layer of bacteria,

4107-472: Is now inside a cell, and the protein can now be expressed. A variety of systems, such as inducible promoters and specific cell-signaling factors, are available to help express the protein of interest at high levels. Large quantities of a protein can then be extracted from the bacterial or eukaryotic cell. The protein can be tested for enzymatic activity under a variety of situations, the protein may be crystallized so its tertiary structure can be studied, or, in

4218-456: Is occurring by measuring how much of that RNA is present in different samples, assuming that no post-transcriptional regulation occurs and that the levels of mRNA reflect proportional levels of the corresponding protein being produced. It is one of the most basic tools for determining at what time, and under what conditions, certain genes are expressed in living tissues. A western blot is a technique by which specific proteins can be detected from

4329-484: Is susceptible to influence by strong alkaline buffering agents, such as sodium dodecyl sulfate (SDS). The terms northern , western and eastern blotting are derived from what initially was a molecular biology joke that played on the term Southern blotting , after the technique described by Edwin Southern for the hybridisation of blotted DNA. Patricia Thomas, developer of the RNA blot which then became known as

4440-400: Is that DNA fragments can be separated by applying an electric current across the gel - because the DNA backbone contains negatively charged phosphate groups, the DNA will migrate through the agarose gel towards the positive end of the current. Proteins can also be separated on the basis of size using an SDS-PAGE gel, or on the basis of size and their electric charge by using what is known as

4551-412: Is then exposed to a labeled DNA probe that has a complement base sequence to the sequence on the DNA of interest. Southern blotting is less commonly used in laboratory science due to the capacity of other techniques, such as PCR , to detect specific DNA sequences from DNA samples. These blots are still used for some applications, however, such as measuring transgene copy number in transgenic mice or in

Ug99 - Misplaced Pages Continue

4662-457: Is transported between regions). This type of dispersal is rare and is very difficult to predict. This is especially known to rarely occur across thousands of km/mi from South Africa to Western Australia. Molecular biology Though cells and other microscopic structures had been observed in living organisms as early as the 18th century, a detailed understanding of the mechanisms and interactions governing their behavior did not emerge until

4773-699: Is under way to marry resistance against present races with future needs for resistance against Ug99 whenever it arrives. Although Sr5 , Sr21 , Sr9e , Sr7b , Sr11 , Sr6 , Sr8a , Sr9g , Sr9b , Sr30 , Sr17 , Sr9a , Sr9d , Sr10 , SrTmp , Sr38 , and SrMcN are no longer effective in Lebanon , Sr11 , Sr24 , and Sr31 still are which is diagnostic for the absence of Ug99 from Lebanon. Detected in Iraq in 2019. Low-levels of TTKTT were detected in Nepal in 2023, but surveillance has not revealed any propagation in

4884-520: Is used to detect post-translational modification of proteins. Proteins blotted on to the PVDF or nitrocellulose membrane are probed for modifications using specific substrates. A DNA microarray is a collection of spots attached to a solid support such as a microscope slide where each spot contains one or more single-stranded DNA oligonucleotide fragments. Arrays make it possible to put down large quantities of very small (100 micrometre diameter) spots on

4995-541: The Bill Gates Foundation donated $ 40   million towards research into Ug99, to be spent on critical infrastructure in Africa. Scientists are working on breeding strains of wheat that are resistant to UG99. However, wheat is grown in a broad range of environments. This means that breeding programs would have extensive work remaining to get resistance into regionally adapted germplasms even after resistance

5106-565: The Medical Research Council Unit, Cavendish Laboratory , were the first to describe the double helix model for the chemical structure of deoxyribonucleic acid (DNA), which is often considered a landmark event for the nascent field because it provided a physico-chemical basis by which to understand the previously nebulous idea of nucleic acids as the primary substance of biological inheritance. They proposed this structure based on previous research done by Franklin, which

5217-714: The Midwestern United States and Great Plains, and overall was 94% of Pg s on Hordea in 1991. 67% of QCCJ was from barley and 95% of Pg on barley was QCCJ. On wheat, QCCJ was still the most common race but only at 38% of Pg . Continues to threaten barley in the Red River Valley in North Dakota and Minnesota . Higher than normal inoculum production in South Central Oklahoma and the adjacent part of North Texas before

5328-425: The genetic code is a triplet code, where each triplet (called a codon ) specifies a particular amino acid. Furthermore, it was shown that the codons do not overlap with each other in the DNA sequence encoding a protein, and that each sequence is read from a fixed starting point. During 1962–1964, through the use of conditional lethal mutants of a bacterial virus, fundamental advances were made in our understanding of

5439-422: The northern blot , actually did not use the term. Named after its inventor, biologist Edwin Southern , the Southern blot is a method for probing for the presence of a specific DNA sequence within a DNA sample. DNA samples before or after restriction enzyme (restriction endonuclease) digestion are separated by gel electrophoresis and then transferred to a membrane by blotting via capillary action . The membrane

5550-488: The spore types that are known for rust fungi ). P. graminis can complete its life cycle either with or without barberry (the alternate host). P. g. tritici ' s obligately biotrophic lifestyle involves the dramatic up-regulation of particular gene transcriptions, constituting its biotrophy genomic features. These genomic regions have parallels in other eukaryotic plant pathogens. These parallels – between these independently evolved and unrelated sets of genes – show

5661-506: The spore types that are known for rust fungi . Spores are typically deposited close to the source, but long-distance dispersal is also well documented commonly out to hundreds of kilometres/miles. The following three categories of long-distance dispersal are known to occur: This can occur unassisted (the robust nature of the spores allows them to be carried long distances in the air and then deposited by rain-scrubbing) or assisted (typically on human clothing or infected plant material that

SECTION 50

#1732773022664

5772-415: The uredinium . They are spiny and brick-red. Urediniospores are the only type of spores in the rust fungus life cycle that are capable of infecting the host on which they are produced, and this is therefore referred to as the 'repeating stage' of the life cycle. It is the spread of urediniospores that allows infection to spread from one cereal plant to another. This phase can rapidly spread the infection over

5883-453: The 1950s," with the last U.S. outbreak in 1962 destroying 5.2% of the crop. Stem rust has been an ongoing problem dating back to Aristotle 's time (384–322 BC). An early ancient practice by the Romans was one where they would sacrifice red animals such as foxes, dogs, and cows to Robigus ( fem. Robigo ), the rust god. They would perform this ritual in the spring during a festival known as

5994-495: The 1991 season resulted in an epidemic in North Central and northwestern Kansas. Virulent against barley bearing Rpg1 . Down to 26% of Pg s afflicting wheat in the US in 1995, 1% in 1996, and not at all in 1997 or 1998. Not found on barley in 1997 but found again in 1998. The first QCC race (since renamed QCCJ or QCCJB) was detected in the northwest Great Plains in 1988, and by 1990 was over 90% of Pg s on barley in

6105-801: The 20th century, when technologies used in physics and chemistry had advanced sufficiently to permit their application in the biological sciences. The term 'molecular biology' was first used in 1945 by the English physicist William Astbury , who described it as an approach focused on discerning the underpinnings of biological phenomena—i.e. uncovering the physical and chemical structures and properties of biological molecules, as well as their interactions with other molecules and how these interactions explain observations of so-called classical biology, which instead studies biological processes at larger scales and higher levels of organization. In 1953, Francis Crick , James Watson , Rosalind Franklin , and their colleagues at

6216-514: The BSR pathogen for decades. These resistant Sr genes, of which 50 are known, give wheat different resistances to stem rust. The virulence in Uganda was virulent against Sr31 and is specific to Ug99. The massive losses of wheat that have occurred have been devastating, but in recent years the wheat rust epidemic has been effectively controlled through selection and breeding for additional Sr genes. (In

6327-640: The Bradford assay can then be measured using a visible light spectrophotometer , and therefore does not require extensive equipment. This method was developed in 1975 by Marion M. Bradford , and has enabled significantly faster, more accurate protein quantitation compared to previous methods: the Lowry procedure and the biuret assay. Unlike the previous methods, the Bradford assay is not susceptible to interference by several non-protein molecules, including ethanol, sodium chloride, and magnesium chloride. However, it

6438-461: The DNA model was Phoebus Levene , who proposed the "polynucleotide model" of DNA in 1919 as a result of his biochemical experiments on yeast. In 1950, Erwin Chargaff expanded on the work of Levene and elucidated a few critical properties of nucleic acids: first, the sequence of nucleic acids varies across species. Second, the total concentration of purines (adenine and guanine) is always equal to

6549-568: The Robigalia in hopes of the wheat crop being spared from the destruction caused by the rust. Weather records from that time have been reexamined and it has been speculated that the fall of the Roman Empire was due to a string of rainy seasons in which the rust would have been more harsh, resulting in reduced wheat harvests. Laws banning barberry were established in 1660 in Rouen , France. This

6660-566: The US on wheat in 1997 and 1998 – but only in the West across both years. On barley in 1997 but not 1998. 25% of Pg s on wheat in 1991. Traces found growing in northwest Illinois fields, also in 1991. 8% of all Pg s on wheat, barley, and oat in the US in 1997, and 31% in 1998. Displaced the previously dominant TPMK suddenly in 1998. 36% of Pg samples from wheat in 1991 in the United States. Unusually severe in southern Illinois in

6771-409: The United States. Also afflicted wheat until a mass switch away from vulnerable cultivars resulted in complete absence in 1997 or 1998. Barley virulence is temperature-sensitive: from 18–20 °C (64–68 °F) rpg4 and Rpg5 are highly effective, but above 27 °C (81 °F) they are ineffective. Not necessarily distinguishable from QCCJ, used synonymously by some practitioners. Found in

SECTION 60

#1732773022664

6882-437: The array and visualization of the hybridization can be done. Since multiple arrays can be made with exactly the same position of fragments, they are particularly useful for comparing the gene expression of two different tissues, such as a healthy and cancerous tissue. Also, one can measure what genes are expressed and how that expression changes with time or with other factors. There are many different ways to fabricate microarrays;

6993-473: The atomic level. Molecular biologists today have access to increasingly affordable sequencing data at increasingly higher depths, facilitating the development of novel genetic manipulation methods in new non-model organisms. Likewise, synthetic molecular biologists will drive the industrial production of small and macro molecules through the introduction of exogenous metabolic pathways in various prokaryotic and eukaryotic cell lines. Horizontally, sequencing data

7104-403: The bacteriophage's protein coat with radioactive sulphur and DNA with radioactive phosphorus, into two different test tubes respectively. After mixing bacteriophage and E.coli into the test tube, the incubation period starts in which phage transforms the genetic material in the E.coli cells. Then the mixture is blended or agitated, which separates the phage from E.coli cells. The whole mixture

7215-484: The country where it was identified ( Uganda ) and the year of its discovery (1999). It spread to Kenya , then Ethiopia , Sudan and Yemen , and becomes more virulent as it spreads. An epidemic of stem rust on wheat caused by race TTKSK spread across Africa , Asia and the Middle East , causing major concern due to the large numbers of people dependent on wheat for sustenance, thus threatening global food security . In 2011, after it had spread into southern Africa ,

7326-459: The decades since, however, Sr31 -virulence has evolved in other strains in other locations. Patpour et al. , 2022 finds it in Spain and Siberia .) United States Department of Agriculture ( USDA ) researchers are testing genes to determine their Ug99 resistance, which will ultimately aid in the development of wheat varieties that will be able to fight off the rust. Resistance has been identified in

7437-493: The development of new technologies and their optimization. Molecular biology has been elucidated by the work of many scientists, and thus the history of the field depends on an understanding of these scientists and their experiments. The field of genetics arose from attempts to understand the set of rules underlying reproduction and heredity , and the nature of the hypothetical units of heredity known as genes . Gregor Mendel pioneered this work in 1866, when he first described

7548-625: The disease is returning to Europe. Comprehensive genomic analysis of Puccinia graminis , combined with plant pathology and climate data, has pointed out the potential of the re-emergence of stem wheat rust in UK. The fungal ancestors of stem rust have infected grasses for millions of years and wheat crops for as long as they have been grown. According to Jim Peterson, professor of wheat breeding and genetics at Oregon State University , "Stem rust destroyed more than 20% of U.S. wheat crops several times between 1917 and 1935, and losses reached 9% twice in

7659-401: The engineering of gene knockout embryonic stem cell lines . The northern blot is used to study the presence of specific RNA molecules as relative comparison among a set of different samples of RNA. It is essentially a combination of denaturing RNA gel electrophoresis , and a blot . In this process RNA is separated based on size and is then transferred to a membrane that is then probed with

7770-431: The epidermis and colonises the leaf. Once inside the leaf the mycelium produces specialised infection structures called pycnia. The pycnia produce two types of haploid gametes, the pycniospores and the receptive hyphae. The pycniospores are produced in a sticky honeydew that attracts insects. The insects carry pycniospores from one leaf to another. Splashing raindrops can also spread pycniospores. A pycniospore can fertilise

7881-412: The experiment involved growing E. coli bacteria in a medium containing heavy isotope of nitrogen ( N) for several generations. This caused all the newly synthesized bacterial DNA to be incorporated with the heavy isotope. After allowing the bacteria to replicate in a medium containing normal nitrogen ( N), samples were taken at various time points. These samples were then subjected to centrifugation in

7992-399: The extract. They discovered that when they digested the DNA in the extract with DNase , transformation of harmless bacteria into virulent ones was lost. This provided strong evidence that DNA was the genetic material, challenging the prevailing belief that proteins were responsible. It laid the basis for the subsequent discovery of its structure by Watson and Crick. Confirmation that DNA is

8103-1054: The first such detection in the country. Found in Nepal in 2023. Virulent on Sr31 , Sr24 , and SrTmp . First detected in Kenya, Rwanda, Uganda, Eritrea, and Egypt in 2014 . Virulent on Sr31 and SrTmp . First detected in Kenya in 2014 . Differs from the original ( TTKSK ) by avirulence against Sr30 . Similar to TTHST . Virulent on Sr31 but avirulent on Sr30 . First detected in Kenya in 2014 . Differs from PTKSK by virulence against SrTmp . Differs from TTKTK by avirulence against Sr21 . Virulent on Sr31 and Sr24 , but avirulent on Sr21 . First detected in Kenya in 2013 . Virulent on Sr31 and Sr24 , but avirulent on Sr30 . First detected in Kenya in 2019 . Virulent to Sr31 , Sr24 , SrTmp , and Sr8155B1 . First detected in Kenya in 2020 . Virulent to Sr31 , Sr24 , and SrTmp , avirulent to Sr30 . Because stem rust (as with many fungi) spreads its spores across long distances with

8214-447: The first week of June, and in west central Indiana , in 1991. TPMK was the worst at 69% of Pg s on wheat in 1997 in the United States – being absent only from the southern Great Plains and the west, but then was down to 10% in 1998. In the upper Great Plains it was already declining – to 26% of samples in 1997, and 12% in 1998. In the most fertile areas of the eastern US it was 96% of Pg s in 1997 but then suddenly fell to 29% in 1998. In

8325-504: The functions and interactions of the proteins employed in the machinery of DNA replication , DNA repair , DNA recombination , and in the assembly of molecular structures. In 1928, Frederick Griffith , encountered a virulence property in pneumococcus bacteria, which was killing lab rats. According to Mendel, prevalent at that time, gene transfer could occur only from parent to daughter cells. Griffith advanced another theory, stating that gene transfer occurring in member of same generation

8436-526: The genetic material which is cause of infection came from the Hershey–Chase experiment . They used E.coli and bacteriophage for the experiment. This experiment is also known as blender experiment, as kitchen blender was used as a major piece of apparatus. Alfred Hershey and Martha Chase demonstrated that the DNA injected by a phage particle into a bacterium contains all information required to synthesize progeny phage particles. They used radioactivity to tag

8547-406: The help of natural air currents , containment is difficult. Advances in fluid mechanics which are commonly used for meteorology have also aided Ug99 dispersal prediction. This is especially important for inter-continental, intermittent spread, such as from Eastern South Africa to Western Australia . Although Ug99 has not yet reached China , other stem rust races already have, and an effort

8658-482: The host range, is expected. Synonymous with QCCJB or known as QCC-2 by some classifications. Most common Pg race in 1991 in the United States , 68% of all Pg samples, and 67% in 1990. Afflicted spring-sown barley in the northern Great Plains in 1990. Was the first barley stem rust to show up in the United States in 1991, in southern Texas in Uvalde . Thought to be responsible for rusting of wild Hordea in

8769-522: The implications of this unique structure for possible mechanisms of DNA replication. Watson and Crick were awarded the Nobel Prize in Physiology or Medicine in 1962, along with Wilkins, for proposing a model of the structure of DNA. In 1961, it was demonstrated that when a gene encodes a protein , three sequential bases of a gene's DNA specify each successive amino acid of the protein. Thus

8880-434: The laws of inheritance he observed in his studies of mating crosses in pea plants. One such law of genetic inheritance is the law of segregation , which states that diploid individuals with two alleles for a particular gene will pass one of these alleles to their offspring. Because of his critical work, the study of genetic inheritance is commonly referred to as Mendelian genetics . A major milestone in molecular biology

8991-408: The leaf sheaths, but are also found on stems , leaves , glumes and awns . On leaves they develop mostly on the underside but may penetrate to the upperside. On leaf sheaths and glumes pustules rupture the epidermis, giving a ragged appearance. Towards the end of the growing season black telia are produced. For this reason stem rust is also known as "black rust". The telia are firmly attached to

9102-418: The leaf surface. So important is its role in maintenance of prevalence that since the near extermination of the alternate host from the northern Great Plains in the United States, epidemics in crops have become rare. Like other Puccinia species, P. graminis is an obligate biotroph (it colonizes living plant cells) and has a complex life cycle featuring alternation of generations . The fungus

9213-415: The most common are silicon chips, microscope slides with spots of ~100 micrometre diameter, custom arrays, and arrays with larger spots on porous membranes (macroarrays). There can be anywhere from 100 spots to more than 10,000 on a given array. Arrays can also be made with molecules other than DNA. Allele-specific oligonucleotide (ASO) is a technique that allows detection of single base mutations without

9324-399: The need for PCR or gel electrophoresis. Short (20–25 nucleotides in length), labeled probes are exposed to the non-fragmented target DNA, hybridization occurs with high specificity due to the short length of the probes and even a single base change will hinder hybridization. The target DNA is then washed and the unhybridized probes are removed. The target DNA is then analyzed for the presence of

9435-480: The original Ug99. Salcedo et al. , 2017 finds its Avr target, AvrSr35 . Races virulent on Sr35 benefit from nonfunctionalization of AvrSr35 by insertion of a mobile element . There are 15 races of Ug99, which (under the North American nomenclature system) have the designations TTKSK, TTKSF, TTKST, TTTSK, TTKSP, PTKSK, PTKST, TTKSF+, TTKTT, TTKTK, TTHSK, PTKTK, TTHST, TTKTT+, and TTHTT. They are all closely related and are believed to have evolved from

9546-463: The pharmaceutical industry, the activity of new drugs against the protein can be studied. Polymerase chain reaction (PCR) is an extremely versatile technique for copying DNA. In brief, PCR allows a specific DNA sequence to be copied or modified in predetermined ways. The reaction is extremely powerful and under perfect conditions could amplify one DNA molecule to become 1.07 billion molecules in less than two hours. PCR has many applications, including

9657-430: The plant may die. Infection can reduce what is an apparently healthy crop about three weeks before harvest into a black tangle of broken stems and shriveled grains by harvest. Stem rust of cereals causes yield losses in several ways: Stem rust on wheat is characterized by the presence of uredinia on the plant, which are brick-red, elongated, blister-like pustules that are easily shaken off. They most frequently occur on

9768-493: The plant tissue. The site of infection is a visible symptom of the disease. Pycnia appear on barberry plants in the spring, usually in the upper leaf surfaces. They are often in small clusters and exude pycniospores in a sticky honeydew. Five to ten days later, cup-shaped structures filled with orange-yellow, powdery aeciospores break through the lower leaf surface. The aecial cups are yellow and sometimes elongate to extend up to 5 millimetres ( 13 ⁄ 64  in) from

9879-418: The plant. The fungus grows inside the plant as a dikaryotic mycelium. Within 1–2 weeks the mycelium produces uredinia and the cycle is complete. Since the urediniospores are produced on the cereal host and can infect the cereal host, it is possible for the infection to pass from one year's crop to the next without infecting the alternate host (barberry). For example, infected volunteer wheat plants can serve as

9990-405: The probe via radioactivity or fluorescence. In this experiment, as in most molecular biology techniques, a control must be used to ensure successful experimentation. In molecular biology, procedures and technologies are continually being developed and older technologies abandoned. For example, before the advent of DNA gel electrophoresis ( agarose or polyacrylamide ), the size of DNA molecules

10101-500: The problem, and most subsequent efforts can be traced to his advocacy. It can cause up to 100% crop losses and is virulent against many resistance genes which have previously protected wheat against stem rust. Although Ug99- resistant varieties of wheat do exist, a screen of 200,000 wheat varieties used in 22 African and Asian countries found that only 5–10% of the area of wheat grown in these countries consisted of varieties with adequate resistance. The original race of Ug99, which

10212-530: The protein of interest can then be visualized by a variety of techniques, including colored products, chemiluminescence , or autoradiography . Often, the antibodies are labeled with enzymes. When a chemiluminescent substrate is exposed to the enzyme it allows detection. Using western blotting techniques allows not only detection but also quantitative analysis. Analogous methods to western blotting can be used to directly stain specific proteins in live cells or tissue sections. The eastern blotting technique

10323-691: The region. As of 2013 it was the US Director of National Intelligence 's assessment that Ug99 would arrive in South Asia soon, in the following few years. This was expected to cause worldwide supply disruptions because, although productivity was growing in Eastern Europe and could theoretically fill that gap, governments worldwide had shown a readiness to forbid exports. Stem rust See § Synonyms Stem rust , also known as cereal rust , black rust , red rust or red dust ,

10434-767: The research being conducted by the USDA , The United Kingdom’s Department for International Development (DFID) along with Bill & Melinda Gates Foundation , announced in February 2011 that they will be granting $ 40 million to a global project led by Cornell University to combat virulent strains of Ug99. The five-year grant to the Durable Rust Resistance in Wheat (DRRW) project supported attempts to identify new resistance genes as well as reproduce and distribute rust resistant wheat seeds to farmers. There has been

10545-433: The rest of the stages remained unknown. Anton de Bary later conducted experiments to observe the beliefs of European farmers regarding the relationship between the rust and barberry plants, and after connecting the basidiospores of the basidia stage to barberry, he also identified that the aeciospores in the aecia stage reinfect the wheat host. Upon de Bary's discovery of all five spore stages and their need for barberry as

10656-432: The spores on the leaf surfaces that range from orange to dark-red in color. Later, the spores change and become dark in color, which gives rise to another common name, "black rust". The North American race nomenclature system was introduced in 1988 by Roelfs and Martens. This nomenclature is a series of letters each of which indicate virulence/avirulence against one resistance gene , as diagnosed by performance against

10767-414: The stem rust. Thirty years later it received its name, Puccinia graminis , by Persoon , and in 1854 brothers Louis René and Charles Tulasne discovered the characteristic five-spore stage that is known in some stem rust species. The brothers were also able to make a connection between the red (urediniospore) and black (teliospore) spores as different stages within the life cycle of the same organism, but

10878-421: The study of gene expression, the detection of pathogenic microorganisms, the detection of genetic mutations, and the introduction of mutations to DNA. The PCR technique can be used to introduce restriction enzyme sites to ends of DNA molecules, or to mutate particular bases of DNA, the latter is a method referred to as site-directed mutagenesis . PCR can also be used to determine whether a particular DNA fragment

10989-532: The study of gene structure and function, has been among the most prominent sub-fields of molecular biology since the early 2000s. Other branches of biology are informed by molecular biology, by either directly studying the interactions of molecules in their own right such as in cell biology and developmental biology , or indirectly, where molecular techniques are used to infer historical attributes of populations or species , as in fields in evolutionary biology such as population genetics and phylogenetics . There

11100-554: The synthesis of a new complementary strand, resulting in two daughter DNA molecules, each consisting of one parental and one newly synthesized strand. The Meselson-Stahl experiment provided compelling evidence for the semiconservative replication of DNA, which is fundamental to the understanding of genetics and molecular biology. In the early 2020s, molecular biology entered a golden age defined by both vertical and horizontal technical development. Vertically, novel technologies are allowing for real-time monitoring of biological processes at

11211-486: The theory of Transduction came into existence. Transduction is a process in which the bacterial DNA carry the fragment of bacteriophages and pass it on the next generation. This is also a type of horizontal gene transfer. The Meselson-Stahl experiment was a landmark experiment in molecular biology that provided evidence for the semiconservative replication of DNA. Conducted in 1958 by Matthew Meselson and Franklin Stahl ,

11322-451: The total concentration of pyrimidines (cysteine and thymine). This is now known as Chargaff's rule. In 1953, James Watson and Francis Crick published the double helical structure of DNA, based on the X-ray crystallography work done by Rosalind Franklin which was conveyed to them by Maurice Wilkins and Max Perutz . Watson and Crick described the structure of DNA and conjectured about

11433-415: The urediniospores that are spiny and are produced on individual stalks. The chains of aeciospores are surrounded by a bell-like enclosure of fungal cells. The aeciospores are able to germinate on the cereal host but not on the alternative host (they are produced on the alternative host, which is usually barberry). They are carried by wind to the cereal host where they germinate and the germ tubes penetrate into

11544-443: The use of molecular biology or molecular cell biology in medicine is now referred to as molecular medicine . Molecular biology sits at the intersection of biochemistry and genetics ; as these scientific disciplines emerged and evolved in the 20th century, it became clear that they both sought to determine the molecular mechanisms which underlie vital cellular functions. Advances in molecular biology have been closely related to

11655-474: Was a landmark study conducted in 1944 that demonstrated that DNA, not protein as previously thought, carries genetic information in bacteria. Oswald Avery , Colin Munro MacLeod , and Maclyn McCarty used an extract from a strain of pneumococcus that could cause pneumonia in mice. They showed that genetic transformation in the bacteria could be accomplished by injecting them with purified DNA from

11766-462: Was an African origin, and in 2018 DNA analysis confirmed that, specifically South African . South Africa itself has an ongoing problem with various stem rust outbreaks which requires better response, including an indigenous breeding for resistance program. There is considerable genetic diversity within the species P. graminis , and several special forms, forma specialis , which vary in host range have been identified. P. graminis

11877-495: Was conveyed to them by Maurice Wilkins and Max Perutz . Their work led to the discovery of DNA in other microorganisms, plants, and animals. The field of molecular biology includes techniques which enable scientists to learn about molecular processes. These techniques are used to efficiently target new drugs, diagnose disease, and better understand cell physiology. Some clinical research and medical therapies arising from molecular biology are covered under gene therapy , whereas

11988-524: Was due to the fact that European farmers noticed a correlation between barberry and stem rust epidemics in wheat. The law banned the planting of barberry near wheat fields and was the first of its kind. The parasitic nature of stem rust was discovered in the 1700s. Two Italian scientists, Fontana and Tozzetti , first explained the stem rust fungus in wheat in 1767. Italian scientist Giuseppe Maria Giovene (1753–1837), in his work Lettera al dottor Cosimo Moschettini sulla ruggine , also thoroughly studied

12099-412: Was partly prompted by the threat it posed to food supplies during World War I . The "war against barberries" was waged and called upon the help of citizens through radio and newspaper advertisements, pamphlets, and fair booths asking for help from all in the attempt to rid the barberry bushes of their existence. Later, in 1975–1980, the program was reestablished under state jurisdiction. Once this happened,

12210-414: Was the discovery of the structure of DNA . This work began in 1869 by Friedrich Miescher , a Swiss biochemist who first proposed a structure called nuclein , which we now know to be (deoxyribonucleic acid), or DNA. He discovered this unique substance by studying the components of pus-filled bandages, and noting the unique properties of the "phosphorus-containing substances". Another notable contributor to

12321-1009: Was the first Ug99 race found to be virulent against Sr gene Sr24 . TTKST is now the predominant stem rust race in Kenya. Virulent on Sr31 . First detected in Kenya in 2007 , Tanzania in 2009 , Ethiopia in 2010 , Uganda in 2012 , and Rwanda in 2014 . Virulent on Sr31 and Sr36 . First detected by Visser et al. , 2011 in South Africa in 2007 . Avirulent on Sr31 and virulent on Sr24 . First detected in Ethiopia in 2007 , Kenya in 2009 , Yemen in 2009 , and South Africa in 2017 . Virulent on Sr31 and avirulent on Sr21 . First detected in Ethiopia in 2007 , Kenya in 2008 , South Africa in 2009 by Visser et al. , 2011, Eritrea and Mozambique and Zimbabwe in 2010 . Virulent on Sr31 and Sr24 , but avirulent on Sr21 . First detected in both South Africa and Zimbabwe in 2010 . Virulent against Sr9h . Avirulent on Sr31 but virulent on Sr9h . First detected in Kenya in 2014 . Also detected in Iraq in 2019,

#663336