Editing Plant pathology (section)

== Plant pathogenicity ==

{{further|Plant disease}}

Plant pathogens, organisms that cause infectious [[plant disease]]s, include [[fungus|fungi]], [[oomycetes]], [[bacterium|bacteria]], [[plant virus|viruses]], [[viroid]]s, [[virus]]-like organisms, [[phytoplasmas]], [[protozoa]], [[nematode]]s and [[parasitic plant]]s.<ref>{{cite journal |last1=Nazarov |first1=Pavel A. |last2=Baleev |first2=Dmitry N. |last3=Ivanova |first3=Maria I. |last4=Sokolova |first4=Luybov M. |last5=Karakozova |first5=Marina V. |date=27 October 2020 |title=Infectious plant diseases: etiology, current status, problems and prospects in plant protection |journal=Acta Naturae |volume=12 |issue=3 |pages=46–59 |doi=10.32607/actanaturae.11026 |pmc=7604890 |pmid=33173596}}</ref>
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In most plant [[pathosystem]]s, [[virulence]] depends on [[hydrolase]]s and enzymes that degrade the [[cell wall]]. The vast majority of these act on [[pectin]]s (for example, [[pectinesterase]], [[pectate lyase]], and [[pectinase]]s). For microbes, the cell wall [[polysaccharide]]s are both a food source and a barrier to be overcome. Many pathogens grow opportunistically when the host breaks down its own cell walls, most often during [[fruit ripening]].<ref name="Cantu-et-al-2008">{{cite journal |last1=Cantu |first1=Dario |last2=Vicente |first2=Ariel R. |last3=Labavitch |first3=John M. |last4=Bennett |first4=Alan B. |last5=Powell |first5=Ann L.T. |title=Strangers in the matrix: plant cell walls and pathogen susceptibility |journal=Trends in Plant Science |date=November 2008 |volume=13 |issue=11 |pages=610–617 |doi=10.1016/j.tplants.2008.09.002 |pmid=18824396 |bibcode=2008TPS....13..610C |hdl=11336/148749 |hdl-access=free}}</ref> Unlike human and animal pathology, plant pathology usually focuses on a single causal organism; however, some plant diseases have been shown to be interactions between multiple pathogens.<ref>{{cite journal |last1=Lamichhane |first1=Jay Ram |last2=Venturi |first2=Vittorio |title=Synergisms between microbial pathogens in plant disease complexes: a growing trend |journal=Frontiers in Plant Science |date=27 May 2015 |volume=06 |page=385 |doi=10.3389/fpls.2015.00385 |doi-access=free |pmid=26074945 |pmc=4445244}}</ref>

To colonize a plant, pathogens have specific [[pathogenicity factor]]s, of five main types: uses of cell wall–degrading enzymes, [[toxins]], effector proteins, [[phytohormone]]s, and [[exopolysaccharide]]s.

* '''Cell wall-degrading enzymes''': These are used to break down the plant [[cell wall]] in order to release the nutrients inside and include esterases, glycosyl hydrolases, lyases and oxidoreductases.<ref>{{cite journal |last1=Giovannoni |first1=Moira |last2=Gramegna |first2=Giovanna |last3=Benedetti |first3=Manuel |last4=Mattei |first4=Benedetta |title=Industrial Use of Cell Wall Degrading Enzymes: The Fine Line Between Production Strategy and Economic Feasibility |journal=Frontiers in Bioengineering and Biotechnology |date=29 April 2020 |volume=8 |page=356 |doi=10.3389/fbioe.2020.00356 |pmid=32411686 |pmc=7200985 |doi-access=free }}</ref>
* '''[[Toxins]]''': These can be non-host-specific, which damage all plants, or host-specific, which cause damage only on a host plant.
* '''[[Effector (biology)|Effector]] proteins''': These can be secreted by pathogens such as bacteria, fungi, and oomycetes<ref name="watermold">{{cite web |last1=Davis |first1=Nicole |url=http://www.broadinstitute.org/news/1328 |title=Genome of Irish potato famine pathogen decoded |publisher=Broad Institute of MIT and Harvard |date=9 September 2009 |access-date=24 July 2012 }}</ref><ref name="Oomycetes">{{cite web |url=http://www.dana-farber.org/Newsroom/News-Releases/First-large-scale-map-of-a-plant-s-protein-network-addresses-evolution,-disease-process.aspx |title=1st large-scale map of a plant's protein network addresses evolution, disease process |date=July 29, 2011 |publisher=Dana-Farber Cancer Institute |access-date=24 July 2012 |url-status=dead |archive-url=https://web.archive.org/web/20120512073154/http://www.dana-farber.org/Newsroom/News-Releases/First-large-scale-map-of-a-plant-s-protein-network-addresses-evolution,-disease-process.aspx |archive-date=12 May 2012 }}</ref> into the extracellular environment or directly into the host cell, often via the [[Type three secretion system]]. Some effectors are known to suppress host immune processes.<ref name=":0">{{Cite journal |last=Derevnina |first=Lida |last2=Contreras |first2=Mauricio P. |last3=Adachi |first3=Hiroaki |last4=Upson |first4=Jessica |last5=Vergara Cruces |first5=Angel |last6=Xie |first6=Rongrong |last7=Skłenar |first7=Jan |last8=Menke |first8=Frank L. H. |last9=Mugford |first9=Sam T. |last10=MacLean |first10=Dan |last11=Ma |first11=Wenbo |last12=Hogenhout |first12=Saskia A. |last13=Goverse |first13=Aska |last14=Maqbool |first14=Abbas |last15=Wu |first15=Chih-Hang |date=2021-08-23 |editor-last=Dong |editor-first=Xinnian |title=Plant pathogens convergently evolved to counteract redundant nodes of an NLR immune receptor network |url=https://dx.plos.org/10.1371/journal.pbio.3001136 |journal=PLOS Biology |language=en |volume=19 |issue=8 |pages=e3001136 |doi=10.1371/journal.pbio.3001136 |issn=1545-7885 |pmc=8412950 |pmid=34424903 |doi-access=free}}</ref> This can include reducing or inhibiting the plant's internal signaling mechanisms or reduction of phytochemicals production.<ref name=":0" /><ref name="effector">{{cite web |url=http://newsroom.ucr.edu/2587 |title=How do plants fight disease? Breakthrough research by UC Riverside plant pathologist offers a clue |publisher=UC Riverside |date=28 March 2011 |last1=Ma |first1=Winbo}}</ref>
* '''[[Phytohormone]]s''' are chemicals used by plants for signaling; pathogens can produce these to modify plant growth to their own advantage.
* '''[[Exopolysaccharide]]s''' are mostly small chains of sugars that help pathogens to adhere to a plant's surface, enabling them to begin the process of infection.