Editing Plant virus (section)

{{Short description|Virus that affects plants}}
{{more citations needed|date=December 2023}}
{{Use dmy dates|date=January 2020}}
[[File:Pepper mild mottle virus.png|thumb|''[[Pepper mild mottle virus]]'']]
[[File:SequoiaBio Leaf Curl.jpg|thumb|right|Leaf curl virus]]
'''Plant viruses''' are [[virus]]es that have the potential to affect [[plant]]s. Like all other viruses, plant viruses are obligate [[intracellular parasite]]s that do not have the molecular machinery to [[Self-replication|replicate]] without a [[host (biology)|host]]. Plant viruses can be [[pathogen]]ic to [[vascular plant|vascular plants ("higher plants")]].

Many plant viruses are [[rod-shaped]], with protein discs forming a tube surrounding the viral [[genome]]; isometric particles are another common structure. They rarely have an [[viral envelope|envelope]]. The great majority have an RNA genome, which is usually small and single stranded (ss), but some viruses have double-stranded (ds) RNA, ssDNA or dsDNA genomes. Although plant viruses are not as well understood as their animal counterparts, one plant virus has become very recognizable: ''[[tobacco mosaic virus]]'' (TMV), the first virus to be discovered. This and other viruses cause an estimated US$60 billion loss in crop yields worldwide each year. Plant viruses are grouped into 73 [[genus (biology)|genera]] and 49 [[family (biology)|families]]. However, these figures relate only to cultivated plants, which represent only a tiny fraction of the total number of plant species. Viruses in wild plants have not been well-studied, but the interactions between wild plants and their viruses often do not appear to cause disease in the host plants.<ref>{{cite journal |last1=Roossinck |first1=Marilyn J. |year=2011 |title=The good viruses: viral mutualistic symbioses |journal=Nature Reviews Microbiology |volume=9 |issue=2|pages=99–108 |doi=10.1038/nrmicro2491 |pmid=21200397 |s2cid=23318905 |doi-access=free }}</ref>

To transmit from one plant to another and from one plant cell to another, plant viruses must use strategies that are usually different from [[animal virus]]es. Most plants do not move, and so plant-to-plant transmission usually involves vectors (such as insects). Plant cells are surrounded by solid [[cell wall]]s, therefore transport through [[plasmodesmata]] is the preferred path for virions to move between plant cells. Plants have specialized mechanisms for transporting [[mRNA]]s through plasmodesmata, and these mechanisms are thought to be used by [[RNA virus]]es to spread from one cell to another.<ref name="Plasmodesmata">{{cite journal |last1=Oparka |first1=Karl J. |last2=Roberts |first2=Alison G. |title=Plasmodesmata. A Not So Open-and-Shut Case |journal=Plant Physiology |volume=125 |issue=1 |date=2001-01-01 |pmid=11154313 |pmc=1539342 |doi=10.1104/pp.125.1.123 |pages=123–126}}</ref> [[Innate immune system#Plants|Plant defenses against viral infection]] include, among other measures, the use of [[siRNA]] in response to [[dsRNA]].<ref>{{Cite book |last1=Alberts |first1=Bruce |last2=Johnson |first2=Alexander |last3=Lewis |first3=Julian |last4=Raff |first4=Martin |last5=Roberts |first5=Keith |last6=Walter |first6=Peter |title=Molecular Biology of the Cell |publisher=Garland Science |year=2002 |isbn=978-0-8153-3218-3 |url=https://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=mboc4 |chapter=7: Control of Gene Expression |pages=451–452}}</ref> Most plant viruses encode a protein to suppress this response.<ref>{{Cite journal |doi=10.1016/j.cell.2007.07.039 |title=Antiviral Immunity Directed by Small RNAs |year=2007 |last1=Ding |first1=Shou-Wei |last2=Voinnet |first2=Olivier |journal=Cell |volume=130 |pages=413–426 |pmid=17693253 |issue=3 |pmc=2703654 }}</ref> Plants also reduce transport through [[plasmodesmata]] in response to injury.<ref name="Plasmodesmata"/>