Cold exposure transiently increases resistance of Arabidopsis thaliana against the fungal pathogen Botrytis cinerea
A sudden cold exposure (4{degrees}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. FundingThis work was supported by the German Research Foundation (CRC973/C4) and the FU Berlin.