Proline related genes expression and physiological changes in indica rice response to water-deficit stress

Abstract

Water deficit stress is a major abiotic stress causing to reduce crop productivity especially rice. Rice has been reported as drought susceptible, which decline plant growth and development in both seedling and reproductive developmental stages. Induced mutant in rice crop against water deficit stress is a fruitful topic. Proline osmolyte is a candidate metabolite to maintain the osmotic pressure in cellular level of water deficit stressed plants. The key enzymes i.e. P5CS, P5CR and ProDH in proline biosynthesis and degradation are well established. In present study, P5CS, P5CR and ProDH and the final product, proline in rice genotypes at booting stage was investigated when subjected to water-deficit and recovery processes. The expression levels of the P5CS gene in PT1 rice (drought susceptible) and the EE12 mutant line were up-regulated when rice genotypes were exposed to severe water-deficit (7% SWC), whereas P5CR genes in NSG19, IR20 and PT1 were up-regulated by the recovery process to a significant degree (p≤0.01). A positive relationship between P5CS expression level and proline content in rice genotypes subjected to water-deficit stress was evidently stated (R 2 = 0.60). In addition, the expression level of ProDH in rice genotypes was exhibited in the recovery process. Moreover, physiological changes, including maximum quantum yield of PSII (F v /F m ), water use efficiency (WUE) and net photosynthetic rate (P n ) were significantly reduced when plants were subjected to severe water-deficit stress (7% SWC), leading to retard plant height.