Chloroplast-mediated activation of plant immunesignalling in Arabidopsis

摘要

Chloroplasts have a critical role in plant immunity as a site for the production for salicylicacid and jasmonic acid, important mediators of plant immunity. However, the molecular linkbetween chloroplasts and the cytoplasmic-nuclear immune system remains largely unknown.Here we show that pathogen-associated molecular pattern (PAMP) signals are quickly relayedto chloroplasts and evoke specific Ca2+ signatures in the stroma. We further demonstrate thata chloroplast-localized protein, named calcium-sensing receptor (CAS), is involved in stromalCa2+ transients and responsible for both PAMP-induced basal resistance and R gene-mediatedhypersensitive cell death. CAS acts upstream of salicylic acid accumulation. Transcriptomeanalysis demonstrates that CAS is involved in PAMP-induced expression of defence genesand suppression of chloroplast gene expression possibly through 1O~2-mediated retrogradesignalling, allowing chloroplast-mediated transcriptional reprogramming during plant immuneresponses. The present study reveals a previously unknown chloroplast-mediated signallingpathway linking chloroplasts to cytoplasmic-nuclear immune responses.