Cold exposure transiently increases resistance ofArabidopsis thalianaagainst the fungal pathogenBotrytis cinerea

ABSTRACT A sudden cold exposure (4°C, 24 h) primes resistance of Arabidopsis thaliana against the virulent biotrophic pathogen Pseudomonas syringae pv. tomato DC3000 ( Pst ) for several days. This effect is mediated by chloroplast cold sensing and the activity of stromal and thylakoid-bound ascorbate peroxidases (sAPX/tAPX). In this study, we investigated the impact of such cold exposure on plant defence against the necrotrophic fungus Botrytis cinerea . Plant resistance was transiently enhanced if the B. cinerea infection occurred immediately after the cold exposure, but this cold-enhanced B. cinerea resistance was absent when the cold treatment and the infection were separated by 5 days at normal growth conditions. Plastid ascorbate peroxidases partially contributed to the transient cold-enhanced resistance against the necrotrophic fungus. In response to B. cinerea , the levels of reactive oxygen species (ROS) were significantly higher in cold-pretreated Arabidopsis leaves. Pathogen-triggered ROS levels varied in the absence of sAPX, highlighting the strong capacity for sAPX-dependent ROS regulation in the chloroplast stroma. The cold-enhanced resistance against B. cinerea was associated with cold-induced plant cell wall modifications, including sAPX-dependent callose formation and significant lignification in cold-treated Arabidopsis leaves. Funding This work was supported by the German Research Foundation (CRC973/C4) and the FU Berlin.