LAUSR

Although accumulating evidence points to the essential roles of nucleus-encoded chloroplast S1 domain-containing proteins (SDPs) in chloroplast RNA metabolism and plant development, functions of chloroplast SDPs in abiotic stress responses are largely unknown. In this study, we investigated the role of a SDP (At1g12800) in Arabidopsis response to diverse abiotic stresses. Analysis of the sdp knockout mutant and complementation lines demonstrated that loss of SDP function results in decreased survival rate of Arabidopsis under salt, heat, UV, or freezing stress, but not under dehydration stress or ABA. In consistent with a previous report demonstrating that SDP is involved in chloroplast rRNA processing, translation in chloroplasts was impaired in the sdp mutant. Expression of several nuclear genes involved in stress response and adaptation was altered in the sdp mutant subjected to different abiotic stresses, suggesting that modulation of chloroplast translation affects the expression of nuclear genes under abiotic stresses. These data reveal that chloroplast-localized SDP plays an important role in abiotic stress response by modulating chloroplast translation and the expression of nuclear genes possibly via unidentified plastid-to-nucleus signaling.