The 30th International Conference on Arabidopsis Research (ICAR 2019)

443 / 2019-02-13 11:49:16

WRKY70 and its homolog WRKY54 negatively modulate the cell wall-associated defenses to necrotrophic pathogens in Arabidopsis

WRKY,cell wall,necrotrophic pathogens,Arabidopsis

Plenary track > Biotic Stress

Previous studies have identified the Arabidopsis thaliana transcription factor WRKY70 as a
node of convergence for salicylic acid (SA) and jasmonic acid (JA)-mediated defense signal
pathways and, together with its closest homolog WRKY54, as a negative regulator of SA
biosynthesis. Here, we demonstrate that WRKY70 together with WRKY54 negatively affect
the response of Arabidopsis to the necrotrophic pathogens Pectobacterium carotovorum
and Botrytis cinerea, but not to the hemibiotroph Pseudomonas syringae pv tomato (Pst)
DC3000, as revealed by mutants studies. Unstressed wrky54wrky70 double mutants exhibited
increased levels of SA, accumulation of hydrogen peroxide (H2O2) and up-regulated
expression of both SA and JA/ethylene (ET) responsive defense related genes. Additionally,
protein cross-linking in cell wall was promoted by endogenous SA, suggesting involvement
of wall-associated defenses against necrotrophs. This response to necrotrophs was compromised
by introducing the sid2-1 allele impairing SA biosynthesis and leading to reduction
of H2O2 content and of defense gene expression. The data suggest that the elevated SA
level in the wrky54wrky70 double mutant results in moderate accumulation of H2O2, in promoting
cell wall fortification and consequently enhanced resistance to necrotrophs but is not
sufficient to trigger hypersensitive reaction (HR)-like cell death and resistance to biotrophs/
hemibiotrophs like Pst DC3000.