Open AccessPopW of Ralstonia solanacearum , a new two‐domain harpin targeting the plant cell wall
Author(s) -
LI JIANGANG,
LIU HONGXIA,
CAO JING,
CHEN LIFENG,
GU CHUN,
ALLEN CAITILYN,
GUO JIANHUA
Publication year - 2010
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.1364-3703.2010.00610.x
Subject(s) - ralstonia solanacearum , biology , mutant , pectate lyase , extracellular , glycine , cell wall , secretion , hypersensitive response , microbiology and biotechnology , amino acid , biochemistry , gene , plant disease resistance , enzyme , pathogen , pectinase
SUMMARY Harpins are extracellular glycine‐rich proteins eliciting a hypersensitive response (HR). In this study, we identified a new harpin, PopW, from Ralstonia solanacearum strain ZJ3721. This 380‐amino‐acid protein is acidic, rich in glycine and serine, and lacks cysteine. When infiltrated into the leaves of tobacco (non‐host), PopW induced a rapid tissue collapse via a heat‐stable but protease‐sensitive HR‐eliciting activity. PopW has an N‐terminal harpin domain (residues 1–159) and a C‐terminal pectate lyase (PL) domain (residues 160–366); its HR‐eliciting activity depends on its N‐terminal domain. Analyses of subcellular localization and plasmolysis demonstrated that PopW targeted the onion cell wall. This was further confirmed by its ability to specifically bind to calcium pectate, a major component of the plant cell wall. However, PopW had no detectable PL activity. Western blotting revealed that PopW was secreted by the type III secretion system in an hrpB ‐dependent manner. Gene sequencing indicated that popW is conserved among 20 diverse strains of R. solanacearum . A popW ‐deficient mutant retained the ability of wild‐type strain ZJ3721 to elicit HR in tobacco and to cause wilt disease in tomato (a host). We conclude that PopW is a new cell wall‐associated, hrpB ‐dependent, two‐domain harpin that is conserved across the R. solanacearum species complex.