Effect Of Water Stress On Physiology And Root Proteome Of Two Genotypic Rice (Oryza Sativa L.) Seedlings

Rice (Oryza sativa L.) is not only the most important crop worldwide, but also the model plant for the monocot families. Water stress is one of the major abiotic stresses limiting the productivity of crops all over the world. It can greatly decrease the rice quantity and quality. Therefore, it is of important theoretical significance and practical value to study the mechanism of drought tolerance and to improve the drought tolerance in rice.A lowland indica cultivar (IR64) and an upland japonica cultivar (Azucena) were used for this study. Three-week old seedlings were treated with 15% PEG-6000 for 7 days. The physiological responses during water stress were investigated, and the root proteomic responses in 2-d stressed seedlings of two rice genotypes were analyzed. The results are summarized as follows:1. The seedlings of IR64 growed better, got the higher biomass and chlorophyll content, and showed fewer changes on photosynthetic parameters (Pn,Gs,Ci,Tr) and root relative water content under water stress. Therefore, lowland rice IR64 showed a stronger tolerance to water stress than upland rice Azucena.2. Root absorbes water directly and is the first organ to perceive soil drought. Thirteen protein spots with significant differential expression between two rice genotypes were detected by 2-DE. Four of them were up-regulated in IR64 roots and down-regulated in Azucena roots, 6 were up-regulated and 3 were down-regulated in both genotypes. Twelve differentially expressed proteins were identified by MALDI-TOF-TOF MS, including PR proteins, and proteins involved in detoxification, protein processing and degradation, enegy production and metabolism. Gene expression analysis of PR-1a, JIOsPR-10, RSOsPR-10 and SAMS by semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) revealed that the mRNA level was not correlated all the time with the protein level and none of them were root -specific expression.Here, the effects of water stress on the physiological responses and root proteome of seedlings between two rice genetypes were compared. The results about different responses between lowland and upland rice were valuable for further understanding water-stress tolerance mechanisms of rice.