systemic signal in plant defence

1. Systemic signals in plant
defence
Presented by:-
Manoj Yadav(13LPMS20)
G. SRAVINI(13LPMS21)

2. 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

3. 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.

4.  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

5. 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.

6. 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.

7. 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.

8. 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.

9. 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.

10. 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.

11. 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.

12. volatile compounds released by
plants
Paré P W , and Tumlinson J H Plant Physiol. 1999;121:325-332

13. SELECTED REFRENCES