Response of two Arabidopsis ecotypes Columbia-0 and Dijon-G to necrotrophic and biotrophic pathogens

Abstract

Arabidopsis thaliana L. ecotype Dijon-G (Di-G) showed a different symptom development during pathogenesis compared to ecotype Columbia-0 (Col-0). Previously, it has been shown that Di-G has a higher susceptibility to necrotrophic fungus Alternaria brassicicola than Col-0. In this study, Di-G showed enhanced disease susceptibility to necrotrophic fungi Botrytis cinerea, Sclerotinia sclerotiorum, and Sclerotium rolfsii known to secrete oxalic acid (OA) as a pathogenicity factor. Treatment with 50 and 100 mM OA resulted in a more leaf tissue collapse in Di-G than in Col-0. The OA also up-regulated expression of the salicylic acid (SA)-inducible pathogenesis-related gene 1 (PR1) and down-regulated expression of the jasmonic acid/ethylene-inducible defensin PDF1.2 gene in Di-G. By contrast, Di-G was resistant to hemibiotrophic fungus Colletotrichum higginsianum and biotrophic Turnip crinkle virus (TCV) infections. Application of 0.5 mM SA resulted in a higher accumulation of endogenous SA and in a preferential expression of SA-responsive genes in Di-G. Salicylic acid accelerated OA-triggered plant cell death and attenuated PDF1.2 expression in Di-G. These results suggest that the enhanced susceptibility of Di-G to necrotrophic pathogen infections might be mediated by attenuated JA-ethylene defence signalling and/or heightened SA-related defence signalling. Interaction of SA-signalling with OA secretion might be also involved in the enhanced susceptibility of Di-G.