Cold Exposure Memory Reduces Pathogen Susceptibility in Based on a Functional Plastid Peroxidase System.

Chloroplasts serve as cold priming hubs modulating the transcriptional response of to a second cold stimulus for several days by postcold accumulation of thylakoid ascorbate peroxidases (tAPX). In an attempt to investigate cross-priming effects of cold on plant pathogen protection, we show here that such a single 24-h cold treatment at 4°C decreased the susceptibility of to virulent pv. DC3000 but did not alter resistance against the avirulent pv. and pv. strains or the effector-deficient pv. strain . The effect of cold priming against pv. was active immediately after cold exposure and memorized for at least 5 days. The priming benefit was established independent of the immune regulator Enhanced Disease Susceptibility 1 (EDS1) or activation of the immune-related genes , , and but required thylakoid-bound as well as stromal ascorbate peroxidase activities because the effect was absent or weak in corresponding knock-out-lines. Suppression of postcold regulation in a conditional-inducible line led to increased bacterial growth numbers. This highlights that the plant immune system benefits from postcold regeneration of the protective chloroplast peroxidase system.[Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.