Systemic signals in plant defence

Presented by:-

Manoj Yadav(13LPMS20)

G. SRAVINI(13LPMS21)

UNIVERSITY OF HYDERABAD

Introduction Efficient communication between the pest colonised

and non- colonised is a vital for the timely menifestation of defence that restrict systemic spread of pest.

Communication requires a mobile ‘systemic signal’. Plants defend themselves against pathogens by a

combination of weapons from two arsenal:

1) Physical barrier (wax, cuticle)

2) Biochemical reactions in tissue of plant

Systemic Acquired Resistance (SAR)

SAR is a mechanism of induced defense that confers long-lasting protection against a broad spectrum of microorganisms.

Enhance resistance against subsequent attack by a wide array of pathogen.

The vasculature provide the excellent channel for transport of systemic signals.

SAR induces the chromatin modification.

SAR can also be

transmitted to the next

generation progeny.

DIR = DEFECTIVE IN INDUCED RESISTANCE1

G3P = glycerol-3-phosphate

DA= Dihydroabetinal amine

NPR1,2 or 3 = signaling receptors

Systemic signals in plant defence

These mobile

signals help in

activation of

SAR.

Mostly metabolites function as systemic signal, contributing to long distance signaling in plant defence.

Methyl salicylate(MeSA) Mobile signal, moves systemically, it found in phloem

exudates of infected leaves, and is required in systemic tissue for SAR

Accumulation of salicylic acid induces the secretion of pathogenesis-related (PR) proteins with antimicrobial activities.

SAR requires SABP2's MeSA esterase activity in the systemic tissue to convert biologically inactive MeSA to active SA. (SABP2’S = Receptor in systemic tissue)

Nicotiana tabaccum contains N resistance gene that governs gene –for –gene type resistance to TMV,MeSA functions as enhance the resistance to subsquent infection by TMV.

Jasmonates

oxylipns ,synthesized from polyunsaturated fatty acid.

Methyl jasmonate (MJ) function as volatile signal and also translocated through the vasculature.

JA activates gene encoding protease inhibitor which protect plants against insect attack.

Treatment of potato with jasmonate increase resistance to Phytophthora infestans.

Azelaic acid

A nine–carbon dicaboxylic acid. Pathogen infection induces the release of free

carbon 18 fatty acids (C18 FA) from membrane lipids, these results in azelaic acid (AzA) production.

AZI1 (AZELAIC ACID INDUCED1) gene, which is expressed at elevated level in azelaic acid-treated plant, was required for defence priming by azelaic acid.

Terpenoids Plant metabolites ,function as in plant growth,

development and stress response. The role of terpenoids in parasitism by weed and in

plant defence against herbivores is widely recognised. Capsidol, polygoidal and gossypol function as

phytoalexins, contributing to direct defence against herbivores and microbes.

Dhydroabictinal, a diterpenoid aldehyde, was purified as a SAR-eliciting factor from petiol exudates(PEs), from avirulent- inoculed Arabidopsis leaves.

Terpenoids Dehydroabietinal induced systemic resistance required

the SID2 (SALICYLIC ACID INDUCTION DEFICIENT2) and NPR1(NONEXPRESSER OF PR GENES1) genes which are involved in SA synthesis and signaling.

Plant Volatiles as a Defense against Insect Herbivores

when a plant is damaged by herbivorous insects, many volatiles are released.

volatile compounds varies with the plant species. They may also induce defense responses in neighbouring

plants. Such chemicals, which function in communication

between and among species, as well as those that serve as messengers between members of the same species, are called semiochemicals.

volatile compounds released by plants

Paré P W , and Tumlinson J H Plant Physiol. 1999;121:325-332

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