PAMP Signaling in Plant Innate Immunity - PAMP Signals in Plant Innate Immunity: Signal Perception and Transduction - page 55

residues). The lectin receptor kinases (LecRKs) contain an extracellular domain of
mannose specifi c binding lectin and an intracellular Ser/Thr kinase catalytic
domain (Barre et al. 2002 ). A mannose-binding lectin (MBL) gene, CaMBL1 , has
been isolated from pepper ( Capsicum annuum ) leaves (Hwang and Hwang 2011 ).
The CaMBL1 gene contains a predicted Galanthus nivalis agglutinin-related lectin
domain responsible for the recognition of high-mannose N -glycans. The CaMBL1
protein exhibits binding specifi city for mannose and is mainly localized to the
plasma membrane. Mannose has been recognized as a PAMP found in fungal
pathogens (Meyer-Wentrup et al. 2007).

2.11.12 RLK Receptor for the PAMP Lipopolysaccharides

The bacterial PAMP lipopolysaccharide (LPS) was found to bind to tobacco cells
and become internalized into endocytic vesicles, suggesting a receptor-mediated
process (Gross et al. 2005 ). It has been suggested that the receptor of the LPS may
be a receptor-like kinase (RLK) (Sanabria and Dubery 2006 ). Further studies are
needed to characterize the PRR for the PAMP LPS.

2.11.13 Peptidoglycan-Binding Proteins

The PRR of the PAMP peptidoglycan is still not known. The LysM motif present
in several receptor kinases and transmembrane proteins in plants can bind pepti-
doglycan (Guan and Mariuzza 2007 ; Zhang et al. 2007b ; Buist et al. 2008 ). It is
likely that these proteins may function as PRRs for the carbohydrate PAMPs
(Nicaise et al. 2009 ).

2.11.14 Pep Receptors for the HAMPs Pep Proteins

Two receptors for the perception of At Pep1 have been recognized in Arabidopsis .
The Pep1 receptor, PEPR1, and the gene encoding the receptor have been isolated
from Arabidopsis suspension-cultured cells (Yamaguchi et al. 2006 ). PEPR1 is a
typical LRR receptor kinase, having an extracellular LRR domain and an intracel-
lular protein kinase domain, and belongs to the LRR XI subfamily of the 15 LRR-
RLK subfamilies (Shiu et al. 2004 ; Qi et al. 2010 ). At PEPR1 has guanylyl cyclase
activity, generating cGMP from GTP, and the cGMP can activate CNGC2-dependent
cytosolic Ca 2+ elevation (Qi et al. 2010 ).
The second Pep1 receptor,PEPR2, has been identifi ed by Yamaguchi et al.
( 2010 ).It is a plasma membrane LRR receptor kinase and has 76 % amino acid simi-
larity to PEPR1 (Yamaguchi et al. 2010 ). PEPR1 has been identifi ed as a receptor