{{Short description|Plant defence mechanism against pathogens}} {{section move to|Biotic stress|section={{section link|Biotic stress|Response to stress}}|date=November 2021}} '''Induced systemic resistance''' ('''ISR''') is a resistance mechanism in plants that is activated by infection.<ref>{{Cite journal |date=2007-12-08 |title=Induced systemic resistance (ISR) in plants: mechanism of action |url=https://pubmed.ncbi.nlm.nih.gov/23100680 |journal=Indian Journal of Microbiology |volume=47 |issue=4 |pages=289–297 |doi=10.1007/s12088-007-0054-2 |issn=0046-8991 |pmc=3450033 |pmid=23100680}}</ref> Its mode of action does not depend on direct killing or inhibition of the invading pathogen, but rather on increasing physical or chemical barrier of the host plant.<ref>{{cite journal |last1=Choudhary |first1=Devendra K. |last2=Prakash |first2=Anil |last3=Johri |first3=B. N. |title=Induced systemic resistance (ISR) in plants: mechanism of action |journal=Indian Journal of Microbiology |date=December 2007 |volume=47 |issue=4 |pages=289–297 |doi=10.1007/s12088-007-0054-2 |pmid=23100680 |pmc=3450033}}</ref> Like the Systemic Acquired Resistance (SAR) a plant can develop defenses against an invader such as a pathogen or parasite if an infection takes place. In contrast to SAR, which is triggered by the accumulation of salicylic acid, ISR instead relies on signal transduction pathways activated by jasmonate and ethylene.<ref>{{cite journal |last1=Yan |first1=Zhinong |last2=Reddy |first2=M. S. |last3=Ryu |first3=Choong-Min |last4=McInroy |first4=John A. |last5=Wilson |first5=Mark |last6=Kloepper |first6=Joseph W. |title=Induced Systemic Protection Against Tomato Late Blight Elicited by Plant Growth-Promoting Rhizobacteria |journal=Phytopathology |date=December 2002 |volume=92 |issue=12 |pages=1329–1333 |doi=10.1094/phyto.2002.92.12.1329 |pmid=18943888 |doi-access=free|bibcode=2002PhPat..92.1329Y }}</ref>

== Discovery ==

The induction of plant-induced resistance to pathogen protection was identified in 1901 and was described as the "system of acquired resistance." Subsequently, several different terms have been used, namely, "acquired physiological immunity", "resistance displacement", "plant immune function" and "induced system resistance."<ref>{{cite journal |vauthors=Conrath U |title=Systemic acquired resistance |journal=Plant Signaling & Behavior |volume=1 |issue=4 |pages=179–84 |date=July 2006 |pmid=19521483 |pmc=2634024|doi=10.4161/psb.1.4.3221 |bibcode=2006PlSiB...1..179C }}</ref> Many forms of stimulus have been found to induce the plant to the virus, bacteria and fungi and other disease resistance including mechanical factors (dry ice damage, electromagnetic, ultraviolet, and low temperature and high temperature treatment, etc.), chemical factors (heavy metal salts, water, salicylic acid), and biological factors (fungi, bacteria, viruses, and their metabolites).<ref>{{cite journal |last1=Walters |first1=Dale R. |last2=Ratsep |first2=Jaan |last3=Havis |first3=Neil D. |title=Controlling crop diseases using induced resistance: challenges for the future |journal=Journal of Experimental Botany |date=March 2013 |volume=64 |issue=5 |pages=1263–1280 |doi=10.1093/jxb/ert026 |pmid=23386685 |doi-access=free}}</ref>

== Mode of action == Induced resistance of plants has 2 major modes of action: the SAR pathway and the ISR pathway. SAR can elicit a rapid local reaction, or hypersensitive response, the pathogen is limited to a small area of the site of infection. As mentioned, salicylic acid (SA) is the mode of action for the SAR pathway. ISR enhances the defense systems of the plant by jasmonic acid (JA) mode of action. Both act on the effect of the NPR-1, but SAR utilizes PR genes. It is important to note that the two mediated responses have regulatory effects on one another. As SA goes up, it can inhibit the effect of JA. There is a balance to be maintained when activating both responses.<ref>{{cite journal |last1=Traw |first1=M. Brian |last2=Bergelson |first2=Joy |title=Interactive Effects of Jasmonic Acid, Salicylic Acid, and Gibberellin on Induction of Trichomes in Arabidopsis |journal=Plant Physiology |date=1 November 2003 |volume=133 |issue=3 |pages=1367–1375 |doi=10.1104/pp.103.027086 |pmid=14551332 |pmc=281631}}</ref>

ISR responses can be mediated by rhizobacteria. This has shown to be effective against necrotrophic pathogens and insect herbivores that are sensitive to JA/ET defenses.<ref>{{cite journal |last1=Pieterse |first1=Corné M.J. |last2=Zamioudis |first2=Christos |last3=Berendsen |first3=Roeland L. |last4=Weller |first4=David M. |last5=Van Wees |first5=Saskia C.M. |last6=Bakker |first6=Peter A.H.M. |title=Induced Systemic Resistance by Beneficial Microbes |journal=Annual Review of Phytopathology |date=4 August 2014 |volume=52 |issue=1 |pages=347–375 |doi=10.1146/annurev-phyto-082712-102340 |pmid=24906124 |bibcode=2014AnRvP..52..347P |hdl=1874/297859 |s2cid=207551516 |hdl-access=free}}</ref> The importance of rhizobacteria-mediated ISR has been widely reported.<ref>{{cite journal |last1=Pieterse |first1=Corné M.J. |last2=Van Pelt |first2=Johan A. |last3=Van Wees |first3=Saskia C.M. |last4=Ton |first4=Jurriaan |last5=Léon-Kloosterziel |first5=Karen M. |last6=Keurentjes |first6=Joost J.B. |last7=Verhagen |first7=Bas W.M. |last8=Knoester |first8=Marga |last9=Van Der Sluis |first9=Ientse |last10=Bakker |first10=Peter A.H.M. |last11=Van Loon |first11=L.C. |title=Rhizobacteria-mediated Induced Systemic Resistance: Triggering, Signalling and Expression |journal=European Journal of Plant Pathology |date=2001 |volume=107 |issue=1 |pages=51–61 |doi=10.1023/a:1008747926678 |bibcode=2001EJPP..107...51P |hdl=1874/7715 |s2cid=24450948 |hdl-access=free}}</ref><ref>{{cite journal |last1=Siddiqui |first1=I. A. |last2=Shaukat |first2=S. S. |title=Rhizobacteria-mediated Induction of Systemic Resistance (ISR) in Tomato against ''Meloidogyne javanica'' |journal=Journal of Phytopathology |date=September 2002 |volume=150 |issue=8–9 |pages=469–473 |doi=10.1046/j.1439-0434.2002.00784.x|bibcode=2002JPhyt.150..469S }}</ref><ref>{{cite journal |last1=Bakker |first1=P. A. H. M. |last2=Ran |first2=L. X. |last3=Pieterse |first3=C. M. J. |last4=van Loon |first4=L. C. |title=Understanding the involvement of rhizobacteria-mediated induction of systemic resistance in biocontrol of plant diseases |journal=Canadian Journal of Plant Pathology |date=March 2003 |volume=25 |issue=1 |pages=5–9 |doi=10.1080/07060660309507043 |bibcode=2003CaJPP..25....5B |hdl=1874/7767 |s2cid=15977931|hdl-access=free }}</ref>

The biological factors of plant-induced system resistance generally include two broad categories, namely classical plant-induced resistance to disease induction (PGPR) or fungi that promote plant growth (PGPF), and plant growth-promoting rhizosphere bacteria (PGPR) or plant growth promoting fungi (PGPF). The difference is mainly due to the fact that the latter can effectively promote plant growth and increase crop yield while causing (or increasing) plant resistance to diseases (sometimes including pests).<ref>{{cite journal |last1=Beneduzi |first1=Anelise |last2=Ambrosini |first2=Adriana |last3=Passaglia |first3=Luciana M.P. |title=Plant growth-promoting rhizobacteria (PGPR): their potential as antagonists and biocontrol agents |journal=Genetics and Molecular Biology |date=2012 |volume=35 |issue=4 suppl 1 |pages=1044–1051 |doi=10.1590/S1415-47572012000600020 |pmid=23411488 |pmc=3571425}}</ref>

== Effects on insects ==

Some studies have also reported negative effects of beneficial microbes on plant-insect interactions.<ref>{{cite journal |last1=Pineda |first1=Ana |last2=Dicke |first2=Marcel |last3=Pieterse |first3=Corné M.J. |last4=Pozo |first4=María J. |title=Beneficial microbes in a changing environment: are they always helping plants to deal with insects? |journal=Functional Ecology |date=June 2013 |volume=27 |issue=3 |pages=574–586 |doi=10.1111/1365-2435.12050 |bibcode=2013FuEco..27..574P |hdl=1874/276314 |hdl-access=free}}</ref>

== Applied research ==

To date, work on induction of plant systemic resistance has shown that inducing plant system resistance work has important implications for basic and applied research.

Induced resistance applications in melons, tobacco, bean, potato, and rice have achieved significant success. Over the past decade, the study of induced system resistance has become a very active field of research.<ref>{{cite journal |last1=Heil |first1=M. |title=Induced Systemic Resistance (ISR) Against Pathogens in the Context of Induced Plant Defences |journal=Annals of Botany |date=1 May 2002 |volume=89 |issue=5 |pages=503–512 |doi=10.1093/aob/mcf076|pmid=12099523 |pmc=4233886 }}</ref>

Methods to artificially activate the ISR pathway is an active area of research.<ref>{{cite journal |last1=Welling |first1=Linda L |title=Induced resistance: from the basic to the applied |journal=Trends in Plant Science |volume=6 |issue=10 |pages=445–7 |date=October 2001 |pmid=11686134 |doi=10.1016/S1360-1385(01)02046-5 |bibcode=2001TPS.....6..445W |url=https://www.cell.com/trends/plant-science/fulltext/S1360-1385(01)02046-5?large_figure=true&code=cell-site|url-access=subscription }}</ref> The research and application of inducing plant system resistance have been encouraging but are not yet a major factor in controlling plant pathogens. Incorporation into integrated pest management programs have shown some promising results. There is research regarding defense against leaf chewing insect pests, by the activation of jasmonic acid signalling triggered by root-associated microorganisms.<ref>{{cite journal |last1=Jung |first1=Sabine C. |last2=Martinez-Medina |first2=Ainhoa |last3=Lopez-Raez |first3=Juan A. |last4=Pozo |first4=Maria J. |title=Mycorrhiza-Induced Resistance and Priming of Plant Defenses |journal=Journal of Chemical Ecology |date=June 2012 |volume=38 |issue=6 |pages=651–664 |doi=10.1007/s10886-012-0134-6 |pmid=22623151 |bibcode=2012JCEco..38..651J |s2cid=12918193 |hdl=10261/344431 |hdl-access=free}}</ref>

Some ongoing research into ISR includes (1) how to systematically improve the selection of induction factors; (2) the injury of induced factors; (3) the phenomenon of multi-effect of induced factors; (4) the effects of chemical induction factors on environmental factors; (5) Establishment of population stability of multivariate biological inducible factor. Research into ISR is driven largely by a response to pesticide use including 1) Increasing resistance by pathogens to pesticides, 2) the necessity to remove some of the more toxic pesticides from the market, 3) health and environment problems caused as an effect of pesticide use, and 4) the inability of certain pesticides to control some pathogens.<ref>{{Cite book |url=https://books.google.com/books?id=EmRHv9xcpAIC&q=Plant+breeding+for+ISR&pg=PA16 |title=Multigenic and Induced Systemic Resistance in Plants |last1=Sadik |first1=Tuzun |last2=Elizabeth |first2=Bent |date=2006-10-26 |publisher=Springer Science & Business Media |isbn=978-0-387-23266-9 |language=en}}</ref>

== See also == * Plant disease resistance * Systemic acquired resistance

== References == {{Reflist}}

Category:Phytopathology Category:Plant physiology Category:Immune system