Open AccessThe leucine‐rich repeat (LRR) protein, CaLRR1, interacts with the hypersensitive induced reaction (HIR) protein, CaHIR1, and suppresses cell death induced by the CaHIR1 protein
Author(s) -
JUNG HO WON,
HWANG BYUNG KOOK
Publication year - 2007
Publication title -
molecular plant pathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.945
H-Index - 103
eISSN - 1364-3703
pISSN - 1464-6722
DOI - 10.1111/j.1364-3703.2007.00410.x
Subject(s) - arabidopsis , biology , hypersensitive response , pseudomonas syringae , gene , ectopic expression , programmed cell death , microbiology and biotechnology , arabidopsis thaliana , leucine rich repeat , plant disease resistance , genetics , mutant , apoptosis
SUMMARY Leucine‐rich repeat proteins (LRRs) function in a number of signal transduction pathways via protein–protein interactions. The gene encoding a small protein of pepper, CaLRR1 , is specifically induced upon pathogen challenge and treatment with pathogen‐associated molecular patterns (PAMPs). We identified a pepper hypersensitive induced reaction (CaHIR1) protein that interacts with the LRR domain of the CaLRR1 protein using yeast two‐hybrid screening. Ectopic expression of the pepper CaHIR1 gene induces cell death in tobacco and Arabidopsis, indicating that the CaHIR1 protein may be a positive regulator of HR‐like cell death. Because transformation is very difficult in pepper plants, we over‐expressed CaLRR1 and CaHIR1 in Arabidopsis to determine cellular functions of the two genes. The over‐expression of the CaHIR1 gene, but not the CaLRR1 gene, in transgenic Arabidopsis confers disease resistance in response to Pseudomonas syringae infection, accompanied by the strong expression of PR genes, the accumulation of both salicylic acid and H 2 O 2 , and K + efflux in plant cells. In Arabidopsis and tobacco plants over‐expressing both CaHIR1 and CaLRR1 , the CaLRR1 protein suppresses not only CaHIR1 ‐induced cell death, but also PR gene expression elicited by CaHIR1 via its association with HIR protein. We propose that the CaLRR1 protein functions as a novel negative regulator of CaHIR1‐mediated cell death responses in plants.