Down-regulation of OsPDCD5, a homolog of the mammalian PDCD5, increases rice tolerance to salt stress

Environmental stresses influence the growth of plants and the productivity of crops. Salinity is one of the most important abiotic stresses for agricultural crops. Programmed cell death (PCD) is induced by a variety of biotic and abiotic stresses in plants, including high salinity treatment. OsPDCD5, an ortholog of the mammalian-programmed cell death 5 gene, is up-regulated under low temperature and salt treatments in rice (Oryza sativa). In this study, transgenic rice that constitutively expressed antisense-OsPDCD5 increased salt stress tolerance in unique ways by inhibiting PCD pathways and regulating specific groups of stress-related genes. Real-time quantitative PCR analysis showed that PCD pathways were inhibited under both normal conditions and salt stress in transgenic rice. Using transcript microarray analysis, 38 stress-related genes regulated in transgenic rice were identified, which appeared to render the transgenic rice adapted for salt stress conditions. Our results suggested that PCD pathways were inhibited and salt stress signaling pathways were regulated in transgenic rice even under normal growth conditions without stress. PCD was further inhibited and these stress-related genes were further regulated to increase tolerance to high salinity under salt stress conditions, thereby leading to build-up of stress protection mechanisms in transgenic rice.