PAMP Signaling in Plant Innate Immunity - PAMP Signals in Plant Innate Immunity: Signal Perception and Transduction - page 46

The ZmPROPEP1 gene is expressed in response to fungal infection and
jasmonic acid. Treatment of maize leaves with Zm Pep1 induces the expression of
ZmPROPEP1 gene (Huffaker et al. 2011 ). Pretreatment with Zm Pep1 prior to infection
enhances resistance to the southern leaf blight pathogen Cochliobolus heterostro-
phus and the stalk rot pathogen Colletotrichum gramoinicola in maize (Huffaker
et al. 2011 ).

2.11 Plant Pattern Recognition Receptors

2.11.1 Structure of PRRs

PAMPs are perceived by plants as danger signals and these signals trigger a net-
work of signaling systems activating defense responses. Specifi c receptors for the
recognition of PAMPs have been identifi ed in the plant cell plasma membrane and
these receptors are called 'Pattern Recognition Receptors (PRRs)'. PAMPs are per-
ceived as alarm/danger signals by cognate pattern recognition receptors (PRRs)
and the PAMP-PRR complex activates the plant immune system (Takakura et al.
2004 ; Jones and Dangl 2006 ; Altenbach and Robatzek 2007 ; He et al. 2007 ; Wan
et al. 2008a , b ; Iriti and Faoro 2009 ). Several receptors for the PAMPs have been
recognized in plasma membrane of plant cells (Table 2.4 ; Mithöfer et al. 2000 ;
Montesano et al. 2003 ; Fliegmann et al. 2004 ; Ron and Avni 2004 ; Fritz-Laylin
et al. 2005; Altenbach and Robatzek 2007 ; He et al. 2007 ). The PRRs identifi ed to
date are modular proteins harbouring an extracellular domain consisting of leu-
cine-rich repeat (LRR) or lysine motifs (LysM) (Table 2.4 ; Saijo 2010 ; Segonzac

Table 2.4 Structure of plant pattern recognition receptors (PRRs)
PAMP/endogenous elicitor PRR Structure

fl g22 FLS2 LRR-RLK

EFTu EFR LRR-RLK

Ax21 XA21 LRR-LK

Pep1 PEPR1 LRR-RLK

PEP2 PEPR2 LRR-RLK

EIX1 LeEIX1, LeEIX2 LRR-RLP

Chitin CERK1 LysM-RLK

Chitin CEBiP LysM-RLP

β -glucans GBP Glycoside hydrolases

Mannose MBL Lectin receptor kinase

Oligogalacturonides WAK1 Wall-associated RLK

INF1 elicitin NbLRK1 Lectin-like receptor kinase

Capsicein elicitin NgRLK1 PR5 protein kinase

Lipopolysaccharides Receptor RLK

Peptidoglycan Receptor LysM-receptor kinase