Misplaced Pages

#460539

65-402: Cytorhabdovirus gramineae is a plant pathogenic virus of the family Rhabdoviridae . Winter wheat Russian mosaic virus is probably a strain of this species. This plant virus article is a stub . You can help Misplaced Pages by expanding it . Plant pathogen Most phytopathogenic fungi are Ascomycetes or Basidiomycetes . They reproduce both sexually and asexually via

130-508: A root hair they produce a plasmodium which invades the roots . Some abiotic disorders can be confused with pathogen-induced disorders. Abiotic causes include natural processes such as drought , frost , snow and hail ; flooding and poor drainage; nutrient deficiency ; deposition of mineral salts such as sodium chloride and gypsum ; windburn and breakage by storms; and wildfires . Plants are subject to disease epidemics. The introduction of harmful non native organisms into

195-489: A 1993 Nobel to Philip Sharp and Richard Roberts . Catalytic RNA molecules ( ribozymes ) were discovered in the early 1980s, leading to a 1989 Nobel award to Thomas Cech and Sidney Altman . In 1990, it was found in Petunia that introduced genes can silence similar genes of the plant's own, now known to be a result of RNA interference . At about the same time, 22 nt long RNAs, now called microRNAs , were found to have

260-425: A certain amount of time, the message degrades into its component nucleotides with the assistance of ribonucleases . Transfer RNA (tRNA) is a small RNA chain of about 80 nucleotides that transfers a specific amino acid to a growing polypeptide chain at the ribosomal site of protein synthesis during translation. It has sites for amino acid attachment and an anticodon region for codon recognition that binds to

325-537: A country can be reduced by controlling human traffic (e.g., the Australian Quarantine and Inspection Service ). Global trade provides unprecedented opportunities for the introduction of plant pests. In the United States , even to get a better estimate of the number of such introductions would require a substantial increase in inspections. In Australia a similar shortcoming of understanding has

390-663: A different origin: Port inspections are not very useful because inspectors know too little about taxonomy. There are often pests that the Australian Government has prioritised as harmful to be kept out of the country, but which have near taxonomic relatives that confuse the issue. X-ray and electron-beam /E-beam irradiation of food has been trialed as a quarantine treatment for fruit commodities originating from Hawaii . The US FDA ( Food and Drug Administration ), USDA APHIS ( Animal and Plant Health Inspection Service ), producers, and consumers were all accepting of

455-417: A few species. Nematodes are able to cause radical changes in root cells in order to facilitate their lifestyle. A few plant diseases are caused by protozoa such as Phytomonas , a kinetoplastid . They are transmitted as durable zoospores that may be able to survive in a resting state in the soil for many years. Further, they can transmit plant viruses . When the motile zoospores come into contact with

520-686: A negative charge each, making RNA a charged molecule (polyanion). The bases form hydrogen bonds between cytosine and guanine, between adenine and uracil and between guanine and uracil. However, other interactions are possible, such as a group of adenine bases binding to each other in a bulge, or the GNRA tetraloop that has a guanine–adenine base-pair. The chemical structure of RNA is very similar to that of DNA , but differs in three primary ways: Like DNA, most biologically active RNAs, including mRNA , tRNA , rRNA , snRNAs , and other non-coding RNAs , contain self-complementary sequences that allow parts of

585-647: A nucleoprotein called a ribosome. The ribosome binds mRNA and carries out protein synthesis. Several ribosomes may be attached to a single mRNA at any time. Nearly all the RNA found in a typical eukaryotic cell is rRNA. Transfer-messenger RNA (tmRNA) is found in many bacteria and plastids . It tags proteins encoded by mRNAs that lack stop codons for degradation and prevents the ribosome from stalling. The earliest known regulators of gene expression were proteins known as repressors and activators – regulators with specific short binding sites within enhancer regions near

650-552: A nucleus, also contain nucleic acids. The role of RNA in protein synthesis was suspected already in 1939. Severo Ochoa won the 1959 Nobel Prize in Medicine (shared with Arthur Kornberg ) after he discovered an enzyme that can synthesize RNA in the laboratory. However, the enzyme discovered by Ochoa ( polynucleotide phosphorylase ) was later shown to be responsible for RNA degradation, not RNA synthesis. In 1956 Alex Rich and David Davies hybridized two separate strands of RNA to form

715-547: A number of RNA-dependent RNA polymerases that use RNA as their template for synthesis of a new strand of RNA. For instance, a number of RNA viruses (such as poliovirus) use this type of enzyme to replicate their genetic material. Also, RNA-dependent RNA polymerase is part of the RNA interference pathway in many organisms. Many RNAs are involved in modifying other RNAs. Introns are spliced out of pre-mRNA by spliceosomes , which contain several small nuclear RNAs (snRNA), or

SECTION 10

#1732787156461

780-457: A pathogen and determine which molecular parts to extract, inactivate, and use in a vaccine. Small molecules with conventional therapeutic properties can target RNA and DNA structures, thereby treating novel diseases. However, research is scarce on small molecules targeting RNA and approved drugs for human illness. Ribavirin, branaplam, and ataluren are currently available medications that stabilize double-stranded RNA structures and control splicing in

845-528: A plant's defenses. Some slime molds in Phytomyxea cause important diseases, including clubroot in cabbage and its relatives and powdery scab in potatoes. These are caused by species of Plasmodiophora and Spongospora , respectively. Most bacteria associated with plants are saprotrophic and do no harm to the plant itself. However, a small number, around 100 known species, cause disease, especially in subtropical and tropical regions of

910-585: A problem in tropical and subtropical regions. Potato cyst nematodes ( Globodera pallida and G. rostochiensis ) are widely distributed in Europe and the Americas, causing $ 300 million worth of damage in Europe annually. Root knot nematodes have quite a large host range, they parasitize plant root systems and thus directly affect the uptake of water and nutrients needed for normal plant growth and reproduction, whereas cyst nematodes tend to be able to infect only

975-483: A protein that allows transmission by a vector. Plant viruses are generally transmitted by a vector , but mechanical and seed transmission also occur. Vectors are often insects such as aphids ; others are fungi , nematodes , and protozoa . In many cases, the insect and virus are specific for virus transmission such as the beet leafhopper that transmits the curly top virus causing disease in several crop plants. Some nematodes parasitize plant roots . They are

1040-472: A role in the development of C. elegans . Studies on RNA interference earned a Nobel Prize for Andrew Fire and Craig Mello in 2006, and another Nobel for studies on the transcription of RNA to Roger Kornberg in the same year. The discovery of gene regulatory RNAs has led to attempts to develop drugs made of RNA, such as siRNA , to silence genes. Adding to the Nobel prizes for research on RNA, in 2009 it

1105-417: A role in the activation of the innate immune system against viral infections. In the late 1970s, it was shown that there is a single stranded covalently closed, i.e. circular form of RNA expressed throughout the animal and plant kingdom (see circRNA ). circRNAs are thought to arise via a "back-splice" reaction where the spliceosome joins a upstream 3' acceptor to a downstream 5' donor splice site. So far

1170-455: A specific sequence on the messenger RNA chain through hydrogen bonding. Ribosomal RNA (rRNA) is the catalytic component of the ribosomes. The rRNA is the component of the ribosome that hosts translation. Eukaryotic ribosomes contain four different rRNA molecules: 18S, 5.8S, 28S and 5S rRNA. Three of the rRNA molecules are synthesized in the nucleolus , and one is synthesized elsewhere. In the cytoplasm, ribosomal RNA and protein combine to form

1235-431: A specific spatial tertiary structure . The scaffold for this structure is provided by secondary structural elements that are hydrogen bonds within the molecule. This leads to several recognizable "domains" of secondary structure like hairpin loops , bulges, and internal loops . In order to create, i.e., design, RNA for any given secondary structure, two or three bases would not be enough, but four bases are enough. This

1300-809: A variety of disorders. Protein-coding mRNAs have emerged as new therapeutic candidates, with RNA replacement being particularly beneficial for brief but torrential protein expression. In vitro transcribed mRNAs (IVT-mRNA) have been used to deliver proteins for bone regeneration, pluripotency, and heart function in animal models. SiRNAs, short RNA molecules, play a crucial role in innate defense against viruses and chromatin structure. They can be artificially introduced to silence specific genes, making them valuable for gene function studies, therapeutic target validation, and drug development. mRNA vaccines have emerged as an important new class of vaccines, using mRNA to manufacture proteins which provoke an immune response. Their first successful large-scale application came in

1365-402: Is protein synthesis , a universal function in which RNA molecules direct the synthesis of proteins on ribosomes . This process uses transfer RNA ( tRNA ) molecules to deliver amino acids to the ribosome , where ribosomal RNA ( rRNA ) then links amino acids together to form coded proteins. It has become widely accepted in science that early in the history of life on Earth , prior to

SECTION 20

#1732787156461

1430-423: Is a ribozyme . Each nucleotide in RNA contains a ribose sugar, with carbons numbered 1' through 5'. A base is attached to the 1' position, in general, adenine (A), cytosine (C), guanine (G), or uracil (U). Adenine and guanine are purines , and cytosine and uracil are pyrimidines . A phosphate group is attached to the 3' position of one ribose and the 5' position of the next. The phosphate groups have

1495-498: Is called enhancer RNAs .  It is not clear at present whether they are a unique category of RNAs of various lengths or constitute a distinct subset of lncRNAs.  In any case, they are transcribed from enhancers , which are known regulatory sites in the DNA near genes they regulate.  They up-regulate the transcription of the gene(s) under control of the enhancer from which they are transcribed. At first, regulatory RNA

1560-419: Is likely why nature has "chosen" a four base alphabet: fewer than four would not allow the creation of all structures, while more than four bases are not necessary to do so. Since RNA is charged, metal ions such as Mg are needed to stabilise many secondary and tertiary structures . The naturally occurring enantiomer of RNA is D -RNA composed of D -ribonucleotides. All chirality centers are located in

1625-431: Is not economically viable to try to control them, except when they infect perennial species, such as fruit trees. Most plant viruses have small, single-stranded RNA genomes . Some also have double stranded RNA or single or double stranded DNA . These may encode only three or four proteins : a replicase , a coat protein, a movement protein to facilitate cell to cell movement through plasmodesmata , and sometimes

1690-413: Is processed to mature mRNA. This removes its introns —non-coding sections of the pre-mRNA. The mRNA is then exported from the nucleus to the cytoplasm , where it is bound to ribosomes and translated into its corresponding protein form with the help of tRNA . In prokaryotic cells, which do not have nucleus and cytoplasm compartments, mRNA can bind to ribosomes while it is being transcribed from DNA. After

1755-550: Is used as template for building the ends of eukaryotic chromosomes . Double-stranded RNA (dsRNA) is RNA with two complementary strands, similar to the DNA found in all cells, but with the replacement of thymine by uracil and the adding of one oxygen atom. dsRNA forms the genetic material of some viruses ( double-stranded RNA viruses ). Double-stranded RNA, such as viral RNA or siRNA , can trigger RNA interference in eukaryotes , as well as interferon response in vertebrates . In eukaryotes, double-stranded RNA (dsRNA) plays

1820-547: The D -ribose. By the use of L -ribose or rather L -ribonucleotides, L -RNA can be synthesized. L -RNA is much more stable against degradation by RNase . Like other structured biopolymers such as proteins, one can define topology of a folded RNA molecule. This is often done based on arrangement of intra-chain contacts within a folded RNA, termed as circuit topology . RNA is transcribed with only four bases (adenine, cytosine, guanine and uracil), but these bases and attached sugars can be modified in numerous ways as

1885-498: The RNA World theory. There are indications that the enterobacterial sRNAs are involved in various cellular processes and seem to have significant role in stress responses such as membrane stress, starvation stress, phosphosugar stress and DNA damage. Also, it has been suggested that sRNAs have been evolved to have important role in stress responses because of their kinetic properties that allow for rapid response and stabilisation of

1950-453: The amino acid sequence in the protein that is produced. However, many RNAs do not code for protein (about 97% of the transcriptional output is non-protein-coding in eukaryotes ). These so-called non-coding RNAs ("ncRNA") can be encoded by their own genes (RNA genes), but can also derive from mRNA introns . The most prominent examples of non-coding RNAs are transfer RNA (tRNA) and ribosomal RNA (rRNA), both of which are involved in

2015-583: The galactic center of the Milky Way Galaxy . RNA, initially deemed unsuitable for therapeutics due to its short half-life, has been made useful through advances in stabilization. Therapeutic applications arise as RNA folds into complex conformations and binds proteins, nucleic acids, and small molecules to form catalytic centers. RNA-based vaccines are thought to be easier to produce than traditional vaccines derived from killed or altered pathogens, because it can take months or years to grow and study

Cytorhabdovirus gramineae - Misplaced Pages Continue

2080-414: The genetic code . There are more than 100 other naturally occurring modified nucleosides. The greatest structural diversity of modifications can be found in tRNA , while pseudouridine and nucleosides with 2'-O-methylribose often present in rRNA are the most common. The specific roles of many of these modifications in RNA are not fully understood. However, it is notable that, in ribosomal RNA, many of

2145-475: The 2006 Nobel Prize in Physiology or Medicine for discovering microRNAs (miRNAs), specific short RNA molecules that can base-pair with mRNAs. Post-transcriptional expression levels of many genes can be controlled by RNA interference , in which miRNAs , specific short RNA molecules, pair with mRNA regions and target them for degradation. This antisense -based process involves steps that first process

2210-423: The 3’ to 5’ direction, synthesizing a complementary RNA molecule with elongation occurring in the 5’ to 3’ direction. The DNA sequence also dictates where termination of RNA synthesis will occur. Primary transcript RNAs are often modified by enzymes after transcription. For example, a poly(A) tail and a 5' cap are added to eukaryotic pre-mRNA and introns are removed by the spliceosome . There are also

2275-562: The B-form most commonly observed in DNA. The A-form geometry results in a very deep and narrow major groove and a shallow and wide minor groove. A second consequence of the presence of the 2'-hydroxyl group is that in conformationally flexible regions of an RNA molecule (that is, not involved in formation of a double helix), it can chemically attack the adjacent phosphodiester bond to cleave the backbone. The functional form of single-stranded RNA molecules, just like proteins, frequently requires

2340-768: The RNA so that it can base-pair with a region of its target mRNAs. Once the base pairing occurs, other proteins direct the mRNA to be destroyed by nucleases . Next to be linked to regulation were Xist and other long noncoding RNAs associated with X chromosome inactivation .  Their roles, at first mysterious, were shown by Jeannie T. Lee and others to be the silencing of blocks of chromatin via recruitment of Polycomb complex so that messenger RNA could not be transcribed from them. Additional lncRNAs, currently defined as RNAs of more than 200 base pairs that do not appear to have coding potential, have been found associated with regulation of stem cell pluripotency and cell division . The third major group of regulatory RNAs

2405-410: The RNA to fold and pair with itself to form double helices. Analysis of these RNAs has revealed that they are highly structured. Unlike DNA, their structures do not consist of long double helices, but rather collections of short helices packed together into structures akin to proteins. In this fashion, RNAs can achieve chemical catalysis (like enzymes). For instance, determination of the structure of

2470-507: The RNAs mature. Pseudouridine (Ψ), in which the linkage between uracil and ribose is changed from a C–N bond to a C–C bond, and ribothymidine (T) are found in various places (the most notable ones being in the TΨC loop of tRNA ). Another notable modified base is hypoxanthine , a deaminated adenine base whose nucleoside is called inosine (I). Inosine plays a key role in the wobble hypothesis of

2535-445: The case of the 5S rRNA of the members of the genus Halococcus ( Archaea ), which have an insertion, thus increasing its size. Messenger RNA (mRNA) carries information about a protein sequence to the ribosomes , the protein synthesis factories in the cell. It is coded so that every three nucleotides (a codon ) corresponds to one amino acid. In eukaryotic cells, once precursor mRNA (pre-mRNA) has been transcribed from DNA, it

2600-402: The cell nucleus and is usually catalyzed by an enzyme— RNA polymerase —using DNA as a template, a process known as transcription . Initiation of transcription begins with the binding of the enzyme to a promoter sequence in the DNA (usually found "upstream" of a gene). The DNA double helix is unwound by the helicase activity of the enzyme. The enzyme then progresses along the template strand in

2665-404: The class Mollicutes . Their cells are extremely small, 1 to 2 micrometres across. They tend to have small genomes (roughly between 0.5 and 2 Mb). They are normally transmitted by leafhoppers (cicadellids) and psyllids , both sap-sucking insect vectors. These inject the bacteria into the plant's phloem , where it reproduces. Many plant viruses cause only a loss of crop yield . Therefore, it

Cytorhabdovirus gramineae - Misplaced Pages Continue

2730-498: The dead host cells. Significant fungal plant pathogens include: The oomycetes are fungus-like organisms among the Stramenopiles . They include some of the most destructive plant pathogens, such as the causal agents of potato late blight root rot , and sudden oak death . Despite not being closely related to the fungi, the oomycetes have developed similar infection strategies, using effector proteins to turn off

2795-444: The earliest forms of life (self-replicating molecules) could have relied on RNA both to carry genetic information and to catalyze biochemical reactions—an RNA world . In May 2022, scientists discovered that RNA can form spontaneously on prebiotic basalt lava glass , presumed to have been abundant on the early Earth . In March 2015, DNA and RNA nucleobases , including uracil , cytosine and thymine , were reportedly formed in

2860-414: The evolution of DNA and possibly of protein-based enzymes as well, an " RNA world " existed in which RNA served as both living organisms' storage method for genetic information —a role fulfilled today by DNA, except in the case of RNA viruses —and potentially performed catalytic functions in cells—a function performed today by protein enzymes, with the notable and important exception of the ribosome, which

2925-456: The first crystal of RNA whose structure could be determined by X-ray crystallography. The sequence of the 77 nucleotides of a yeast tRNA was found by Robert W. Holley in 1965, winning Holley the 1968 Nobel Prize in Medicine (shared with Har Gobind Khorana and Marshall Nirenberg ). In the early 1970s, retroviruses and reverse transcriptase were discovered, showing for the first time that enzymes could copy RNA into DNA (the opposite of

2990-646: The four major macromolecules essential for all known forms of life . RNA is assembled as a chain of nucleotides . Cellular organisms use messenger RNA ( mRNA ) to convey genetic information (using the nitrogenous bases of guanine , uracil , adenine , and cytosine , denoted by the letters G, U, A, and C) that directs synthesis of specific proteins. Many viruses encode their genetic information using an RNA genome . Some RNA molecules play an active role within cells by catalyzing biological reactions, controlling gene expression , or sensing and communicating responses to cellular signals. One of these active processes

3055-423: The function of circRNAs is largely unknown, although for few examples a microRNA sponging activity has been demonstrated. Research on RNA has led to many important biological discoveries and numerous Nobel Prizes . Nucleic acids were discovered in 1868 by Friedrich Miescher , who called the material 'nuclein' since it was found in the nucleus . It was later discovered that prokaryotic cells, which do not have

3120-551: The genes to be regulated.   Later studies have shown that RNAs also regulate genes. There are several kinds of RNA-dependent processes in eukaryotes regulating the expression of genes at various points, such as RNAi repressing genes post-transcriptionally , long non-coding RNAs shutting down blocks of chromatin epigenetically , and enhancer RNAs inducing increased gene expression. Bacteria and archaea have also been shown to use regulatory RNA systems such as bacterial small RNAs and CRISPR . Fire and Mello were awarded

3185-664: The ground to take root. Plant diseases cause major economic losses for farmers worldwide. Across large regions and many crop species, it is estimated that diseases typically reduce plant yields by 10% every year in more developed settings, but yield loss to diseases often exceeds 20% in less developed settings. The Food and Agriculture Organization estimates that pests and diseases are responsible for about 25% of crop loss. To solve this, new methods are needed to detect diseases and pests early, such as novel sensors that detect plant odours and spectroscopy and biophotonics that are able to diagnose plant health and metabolism . As of 2018

3250-461: The introns can be ribozymes that are spliced by themselves. RNA can also be altered by having its nucleotides modified to nucleotides other than A , C , G and U . In eukaryotes, modifications of RNA nucleotides are in general directed by small nucleolar RNAs (snoRNA; 60–300 nt), found in the nucleolus and cajal bodies . snoRNAs associate with enzymes and guide them to a spot on an RNA by basepairing to that RNA. These enzymes then perform

3315-472: The laboratory under outer space conditions, using starter chemicals such as pyrimidine , an organic compound commonly found in meteorites . Pyrimidine , like polycyclic aromatic hydrocarbons (PAHs), is one of the most carbon-rich compounds found in the universe and may have been formed in red giants or in interstellar dust and gas clouds. In July 2022, astronomers reported massive amounts of prebiotic molecules , including possible RNA precursors, in

SECTION 50

#1732787156461

3380-601: The local ecosystem. From an economic standpoint, all but the simplest natural additives may disqualify a product from "organic" status, potentially reducing the value of the yield. Crop rotation is a traditional and sometimes effective means of preventing pests and diseases from becoming well-established, alongside other benefits. Other biological methods include inoculation. Protection against infection by Agrobacterium tumefaciens , which causes gall diseases in many plants, can be provided by dipping cuttings in suspensions of Agrobacterium radiobacter before inserting them in

3445-417: The most costly diseases of the most produced crops worldwide are: RNA Ribonucleic acid ( RNA ) is a polymeric molecule that is essential for most biological functions, either by performing the function itself ( non-coding RNA ) or by forming a template for the production of proteins ( messenger RNA ). RNA and deoxyribonucleic acid (DNA) are nucleic acids . The nucleic acids constitute one of

3510-401: The nucleotide modification. rRNAs and tRNAs are extensively modified, but snRNAs and mRNAs can also be the target of base modification. RNA can also be methylated. Like DNA, RNA can carry genetic information. RNA viruses have genomes composed of RNA that encodes a number of proteins. The viral genome is replicated by some of those proteins, while other proteins protect the genome as

3575-693: The physiological state. Bacterial small RNAs generally act via antisense pairing with mRNA to down-regulate its translation, either by affecting stability or affecting cis-binding ability. Riboswitches have also been discovered. They are cis-acting regulatory RNA sequences acting allosterically . They change shape when they bind metabolites so that they gain or lose the ability to bind chromatin to regulate expression of genes. Archaea also have systems of regulatory RNA. The CRISPR system, recently being used to edit DNA in situ , acts via regulatory RNAs in archaea and bacteria to provide protection against virus invaders. Synthesis of RNA typically occurs in

3640-405: The post-transcriptional modifications occur in highly functional regions, such as the peptidyl transferase center and the subunit interface, implying that they are important for normal function. Messenger RNA (mRNA) is the type of RNA that carries information from DNA to the ribosome , the sites of protein synthesis ( translation ) in the cell cytoplasm. The coding sequence of the mRNA determines

3705-928: The process of translation. There are also non-coding RNAs involved in gene regulation, RNA processing and other roles. Certain RNAs are able to catalyse chemical reactions such as cutting and ligating other RNA molecules, and the catalysis of peptide bond formation in the ribosome ; these are known as ribozymes . According to the length of RNA chain, RNA includes small RNA and long RNA. Usually, small RNAs are shorter than 200  nt in length, and long RNAs are greater than 200  nt long. Long RNAs, also called large RNAs, mainly include long non-coding RNA (lncRNA) and mRNA . Small RNAs mainly include 5.8S ribosomal RNA (rRNA), 5S rRNA , transfer RNA (tRNA), microRNA (miRNA), small interfering RNA (siRNA), small nucleolar RNA (snoRNAs), Piwi-interacting RNA (piRNA), tRNA-derived small RNA (tsRNA) and small rDNA-derived RNA (srRNA). There are certain exceptions as in

3770-669: The production of spores and other structures. Spores may be spread long distances by air or water, or they may be soil borne. Many soil inhabiting fungi are capable of living saprotrophically , carrying out the role of their life cycle in the soil . These are facultative saprotrophs. Fungal diseases may be controlled through the use of fungicides and other agricultural practices. However, new races of fungi often evolve that are resistant to various fungicides. Biotrophic fungal pathogens colonize living plant tissue and obtain nutrients from living host cells. Necrotrophic fungal pathogens infect and kill host tissue and extract nutrients from

3835-671: The results - more thorough pest eradication and lesser taste degradation than heat treatment. The International Plant Protection Convention (IPPC) anticipates that molecular diagnostics for inspections will continue to improve. Between 2020 and 2030, IPPC expects continued technological improvement to lower costs and improve performance, albeit not for less developed countries unless funding changes. Many natural and synthetic compounds can be employed to combat plant diseases. This method works by directly eliminating disease-causing organisms or curbing their spread; however, it has been shown to have too broad an effect, typically, to be good for

3900-512: The ribosome—an RNA-protein complex that catalyzes the assembly of proteins—revealed that its active site is composed entirely of RNA. An important structural component of RNA that distinguishes it from DNA is the presence of a hydroxyl group at the 2' position of the ribose sugar . The presence of this functional group causes the helix to mostly take the A-form geometry , although in single strand dinucleotide contexts, RNA can rarely also adopt

3965-423: The usual route for transmission of genetic information). For this work, David Baltimore , Renato Dulbecco and Howard Temin were awarded a Nobel Prize in 1975. In 1976, Walter Fiers and his team determined the first complete nucleotide sequence of an RNA virus genome, that of bacteriophage MS2 . In 1977, introns and RNA splicing were discovered in both mammalian viruses and in cellular genes, resulting in

SECTION 60

#1732787156461

4030-467: The virus particle moves to a new host cell. Viroids are another group of pathogens, but they consist only of RNA, do not encode any protein and are replicated by a host plant cell's polymerase. Reverse transcribing viruses replicate their genomes by reverse transcribing DNA copies from their RNA; these DNA copies are then transcribed to new RNA. Retrotransposons also spread by copying DNA and RNA from one another, and telomerase contains an RNA that

4095-441: The world. Most plant pathogenic bacteria are bacilli . Erwinia uses cell wall–degrading enzymes to cause soft rot . Agrobacterium changes the level of auxins to cause tumours with phytohormones. Significant bacterial plant pathogens include: Phytoplasma and Spiroplasma are obligate intracellular parasites , bacteria that lack cell walls and, like the mycoplasmas , which are human pathogens, they belong to

4160-566: Was awarded for the elucidation of the atomic structure of the ribosome to Venki Ramakrishnan , Thomas A. Steitz , and Ada Yonath . In 2023 the Nobel Prize in Physiology or Medicine was awarded to Katalin Karikó and Drew Weissman for their discoveries concerning modified nucleosides that enabled the development of effective mRNA vaccines against COVID-19. In 1968, Carl Woese hypothesized that RNA might be catalytic and suggested that

4225-405: Was thought to be a eukaryotic phenomenon, a part of the explanation for why so much more transcription in higher organisms was seen than had been predicted. But as soon as researchers began to look for possible RNA regulators in bacteria, they turned up there as well, termed as small RNA (sRNA). Currently, the ubiquitous nature of systems of RNA regulation of genes has been discussed as support for

#460539