Rice Response To Salt Stress And Low Temperature Stress Of Proteome Research

Proteomics studyisplayinganincreasinglyimportantroleinthe functionalgenomicsera.Two-dimensional electrophoresis is one of the key techniques in proteomics studies. Rice(Oryza sativa L.)is not only the most importantcrop worldwide, but also the model plantfor the monocots. We optimized the rice protein extraction method and the electrophoresisconditions, and obtained the high-resolution and reproducible gel maps. At least 1150, 1000,1050 protein spots were detected on the gels of root, leaf and suspension cell, respectively.Thecorrelationcoefficientbetweenreplicatesvariedfrom0.87to0.94.Salt stress is one of the major abiotic stressesaffecting the productivityof crops all overthe world. It was estimated that about 20% of the world land and 50% of all irrigated landwere affected by salinity. There were 34 up-regulated and 20 down-regulated root proteins inthe three-week-old riceseedlings (cv. Nipponbare) treated with 150 mM NaCl for 24, 48 and72h.Massspectrometryanalysishelpedtoidentify12spots representing10differentproteins.Three spots were identified as the same protein enolase. While four of them were previouslyconfirmed as salt stress-responsive proteins, 6 were novel ones, i.e. UDP-glucosepyrophosphorylase, cytochrome c oxidase subunit 6b-1, glutamine synthetase root isozyme,putative nascent polypeptide associated complex alpha chain, putative splicing factor-likeprotein and putative actin-binding protein. These proteins are involved in carbohydrate,nitrogen and energy metabolism, reactive oxygen species scavenging, mRNA and proteinprocessing,andcytoskeletonstability.Low temperature stress is another major abiotic stress limiting the productivity and thegeographical distribution of many important crops. Three-week-old rice seedlings treated at6°C for 6 or 24 h showed stress phenotypes of rolling leaves, increased relative electrolyteleakage and decreased net photosynthetic rate. Among more than 1,000 leaf total proteinsdetected on two-dimensional electrophoresis gels, 31 proteins were down-regulated and 65were up-regulated. Mass spectrometry analysis allowed the identification of 85 differentiallyexpressed proteins, including well-known and novel cold-responsive proteins. Severalproteins showed enhanced degradation during chilling stress, especially the photosyntheticproteins such as Rubisco large subunit, of which 19 fragments were detected. The identifiedproteins are involved in signal transduction, RNAprocessing, translation, protein processing,redox homeostasis, photosynthesis, photorespiration, and metabolisms of carbon, nitrogen,sulfur and energy. Gene expression analysis of 44 different proteins by quantitative real-timePCR revealed that the mRNA level was not correlated well with the protein level.Furthermore, the 41 decreased and 26 increased phosphoproteins stained by Pro-Q Diamondweredetected.