Alfalfa mosaic virus: The type species of the genus ALFAMOVIRUS that is non-persistently transmitted by aphids.Mosaic Viruses: Viruses which produce a mottled appearance of the leaves of plants.Medicago sativa: A plant species of the family FABACEAE widely cultivated for ANIMAL FEED.Ilarvirus: A genus of the family BROMOVIRIDAE which infects mainly woody plants. Species are divided into ten subgroups. Tobacco streak virus is the type species.Alfamovirus: A genus of the family BROMOVIRIDAE with a wide host range. Transmission is by aphids and the type species is ALFALFA MOSAIC VIRUS.Plants, Toxic: Plants or plant parts which are harmful to man or other animals.RNA, Viral: Ribonucleic acid that makes up the genetic material of viruses.Tobacco: A plant genus of the family SOLANACEAE. Members contain NICOTINE and other biologically active chemicals; its dried leaves are used for SMOKING.Plant Viral Movement Proteins: Viral proteins that facilitate the movement of viruses between plant cells by means of PLASMODESMATA, channels that traverse the plant cell walls.Capsid: The outer protein protective shell of a virus, which protects the viral nucleic acid.Protoplasts: The protoplasm and plasma membrane of plant, fungal, bacterial or archaeon cells without the CELL WALL.Plant Viruses: Viruses parasitic on plants higher than bacteria.RNA Replicase: An enzyme that catalyses RNA-template-directed extension of the 3'- end of an RNA strand by one nucleotide at a time, and can initiate a chain de novo. (Enzyme Nomenclature, 1992, p293)Capsid Proteins: Proteins that form the CAPSID of VIRUSES.Bromovirus: A genus of tripartite plant viruses in the family BROMOVIRIDAE. Transmission is by beetles. Brome mosaic virus is the type species.Tobacco Mosaic Virus: The type species of TOBAMOVIRUS which causes mosaic disease of tobacco. Transmission occurs by mechanical inoculation.Viral Proteins: Proteins found in any species of virus.Base Sequence: The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.Virus Replication: The process of intracellular viral multiplication, consisting of the synthesis of PROTEINS; NUCLEIC ACIDS; and sometimes LIPIDS, and their assembly into a new infectious particle.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Nucleic Acid Conformation: The spatial arrangement of the atoms of a nucleic acid or polynucleotide that results in its characteristic 3-dimensional shape.Cucumovirus: A genus of plant viruses of the family BROMOVIRIDAE, which infect cucurbits and solanaceous plants. Transmission occurs via aphids in a non-persistent manner, and also via seeds. The type species Cucumber mosaic virus, a CUCUMOVIRUS, should not be confused with Cucumber green mottle mosaic virus, a TOBAMOVIRUS.Plants, Genetically Modified: PLANTS, or their progeny, whose GENOME has been altered by GENETIC ENGINEERING.Protein Biosynthesis: The biosynthesis of PEPTIDES and PROTEINS on RIBOSOMES, directed by MESSENGER RNA, via TRANSFER RNA that is charged with standard proteinogenic AMINO ACIDS.Caulimovirus: A genus of PLANT VIRUSES, in the family CAULIMOVIRIDAE, that are transmitted by APHIDS in a semipersistent manner. Aphid-borne transmission of some caulimoviruses requires certain virus-coded proteins termed transmission factors.Amino Acid Sequence: The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.Plant Diseases: Diseases of plants.Comovirus: A genus of plant viruses of the family COMOVIRIDAE in which the bipartite genome is encapsidated in separate icosahedral particles. Mosaic and mottle symptoms are characteristic, and transmission is exclusively by leaf-feeding beetles. Cowpea mosaic virus is the type species.Genes, Viral: The functional hereditary units of VIRUSES.Virion: The infective system of a virus, composed of the viral genome, a protein core, and a protein coat called a capsid, which may be naked or enclosed in a lipoprotein envelope called the peplos.3' Untranslated Regions: The sequence at the 3' end of messenger RNA that does not code for product. This region contains transcription and translation regulating sequences.Plants: Multicellular, eukaryotic life forms of kingdom Plantae (sensu lato), comprising the VIRIDIPLANTAE; RHODOPHYTA; and GLAUCOPHYTA; all of which acquired chloroplasts by direct endosymbiosis of CYANOBACTERIA. They are characterized by a mainly photosynthetic mode of nutrition; essentially unlimited growth at localized regions of cell divisions (MERISTEMS); cellulose within cells providing rigidity; the absence of organs of locomotion; absence of nervous and sensory systems; and an alternation of haploid and diploid generations.RNA Viruses: Viruses whose genetic material is RNA.Peptide Chain Initiation, Translational: A process of GENETIC TRANSLATION whereby the formation of a peptide chain is started. It includes assembly of the RIBOSOME components, the MESSENGER RNA coding for the polypeptide to be made, INITIATOR TRNA, and PEPTIDE INITIATION FACTORS; and placement of the first amino acid in the peptide chain. The details and components of this process are unique for prokaryotic protein biosynthesis and eukaryotic protein biosynthesis.Tymovirus: A genus of plant viruses, in the family TYMOVIRIDAE, possessing a narrow host range that includes CRUCIFERAE. Transmission occurs by BEETLES and mechanical inoculation.Potyvirus: A large genus of plant viruses of the family POTYVIRIDAE which infect mainly plants of the Solanaceae. Transmission is primarily by aphids in a non-persistent manner. The type species is potato virus Y.Potexvirus: A genus of plant viruses in the family FLEXIVIRIDAE, that cause mosaic and ringspot symptoms. Transmission occurs mechanically. Potato virus X is the type species.Cloning, Molecular: The insertion of recombinant DNA molecules from prokaryotic and/or eukaryotic sources into a replicating vehicle, such as a plasmid or virus vector, and the introduction of the resultant hybrid molecules into recipient cells without altering the viability of those cells.Transcription, Genetic: The biosynthesis of RNA carried out on a template of DNA. The biosynthesis of DNA from an RNA template is called REVERSE TRANSCRIPTION.Cucumber Mosaic Virus Satellite: A satellite RNA (not a satellite virus) which has several types. Different cucumoviruses can act as helper viruses for different types.RNA, Messenger: RNA sequences that serve as templates for protein synthesis. Bacterial mRNAs are generally primary transcripts in that they do not require post-transcriptional processing. Eukaryotic mRNA is synthesized in the nucleus and must be exported to the cytoplasm for translation. Most eukaryotic mRNAs have a sequence of polyadenylic acid at the 3' end, referred to as the poly(A) tail. The function of this tail is not known for certain, but it may play a role in the export of mature mRNA from the nucleus as well as in helping stabilize some mRNA molecules by retarding their degradation in the cytoplasm.Plant Leaves: Expanded structures, usually green, of vascular plants, characteristically consisting of a bladelike expansion attached to a stem, and functioning as the principal organ of photosynthesis and transpiration. (American Heritage Dictionary, 2d ed)Mutation: Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.Structure-Activity Relationship: The relationship between the chemical structure of a compound and its biological or pharmacological activity. Compounds are often classed together because they have structural characteristics in common including shape, size, stereochemical arrangement, and distribution of functional groups.Vaccinia virus: The type species of ORTHOPOXVIRUS, related to COWPOX VIRUS, but whose true origin is unknown. It has been used as a live vaccine against SMALLPOX. It is also used as a vector for inserting foreign DNA into animals. Rabbitpox virus is a subspecies of VACCINIA VIRUS.