Analysis Of Bioinformation And Data Related To Proteome Of Rice Under Drought Stress

Drought is one of the major abiotic stresses limiting the productivity and the geographical distribution of many important crops.Rice(Oryza sativa L.) is not only the most important crop worldwide,but also the model plant for the monocots.Omics techniques are effective approaches that have in recent years been adopted to study the mechanism of response to stress in plants.Here,through bioinformatic analysis,we investigated the correlations among proteomic,transcriptomic,metabolomic data to uncover the molecular responses of rice plant to drought stress.Drought stress was applied to four-week-old rice seedings(IRAT109,upland variety) by withholding water for 3 days.Drought treatment resulted in leaf rolling,increased relative electrolyte leakage and proline content,and decreased leaves water potential.The decreasing relative soil water content was also monitored.The changes of total proteins in rice leaves were examined using two-dimensional electrophoresis.Among more than 1200 proteins spots reproducibly detected on each gel, 71 differentially expressed protein spots with higher than 1.5-fold change in spot density were founded by T-test(48 were upregulated and 23 were down regulated). MALDI-TOF-TOF-MS analysis allowed the identification of 60 differentially expressed proteins,most of which were drought-inducible proteins previously reported,four were novel proteins appeared under drought stress which were not reported so far.These included adenosylhomocysteinase,ketol-acid reductoisomerase,sucroce-UDP glucosyltransferase 2,formate dehydrogenase.According to Expasy,KEGG and NCBI database and related literature references,these proteins may approximately be classified into 6 functional categories such as,regulatory factor,redox homeostasis,metabolism and energy,cytoskeleton et al.,while the largest functional group(40%of the total) was proteins involved in regulatory factor.Transcript profiling of rice genes was performed using rice DNA microarray and validated by RT-PCR.A total of 4427 rice genes were found differentially expressed,and the Pearson's correlation coefficient of microarray and RT-PCR was 0.95.The most differentially expressed mRNAs belong to 7 categories through Gene ontology(GO) analysis:cell,cell part,organelle,binding,cataltic,celluar process and metabolic process, which,in general,well matched with proteomic data.Comparison of the over all differentially expressed protein levels with their corresponding mRNA levels showed a poor correlation(r=0.08).Particularly,proteins involved in different functional categories showed differen correlation to those of mRNAs:regulatory factor group was-0.35 and dought related proteins was 0.82.To investigate variation of whole metabolites,metabolic fingerprinting analysis of rice leaves was carried out by gas chromatograph(GC) and gas chromatograph-mass spectrometry(GC-MS).A tatol of 129 metabolites were identified.Principal Component Analysis(PCA) base on these metabolites discriminated stressed group from normal group products.Among these metabolites,38 metabolites were found significantly differentially expressed,including amino acids,glucide,and organic acid.after evaluation by pathway and biological process analysis programs,the differentially expressed proteins are demonstrated to be involved with a high degree of confidence(P＜0.05) in Carbon fixation,Pentose phosphate pathway,Glycolysis / Gluconeogenesis.And it was found that Aspartic acid,a component of the most remarkable Carbon fixation pathway,is significantly elevated to 2.7-fold by drought stress as compared with the controls.