Peptidomics Study Of Rice Responds To Salt Stress And Identification Of Bioactive Peptides

Rice(Oryza sativa L.)is a cereal crop of the gramineous rice genus,originating in China and India,which is an important grain crop and monocot model species.As the major food source for more than half of the world’s population,ensuring the production and quality of rice is a very important issue for global food security.Rice is a saltsensitive crop,especially in the seedling stage and reproductive stage,the tolerance to salt stress will be weaker.In recent years,the phenomenon of soil salinization has shown a globally trend of spreading and increasing,which has caused serious challenges to the growth and development of rice crops.Peptide is an important compound in cells,which is widely used as signaling molecules for cell-to-cell communication in animals and plants.Peptidomics,the comprehensive qualitative and quantitative analysis of all peptides in a biological sample.As an emerging research method,peptidomics provide us with a novel viewpoint to solve biology problems.In this study,we used rice as the research object,using two research methods,quantitative peptidomics and phosphpeptidomics,to study and analyze rice seedlings under salt stress.Combining relevant physiological and biochemical indices to further understand the molecular mechanism of rice response to salt tolerance.In addition,we also analyzed functional identification of the three differentially expressed peptides Os STPE1,Os STPE2,and Os STPE3,which were identified in quantitative peptidomics.We guessed that they are related to the rice responding to salt stress.The main results and conclusions obtained are as follows:1.The rice seedlings under different salt treatment conditions were subjected to peptide extraction using quantitative peptidomics.911,1263 nonredundant peptides were respectively identified in the two TMT-6plex labeling mixed samples,which were extracted from the root tissue of rice seedlings,Sample-1 and Sample-2.770,673 nonredundant peptides were respectively identified in the two TMT-6plex labeling mixed samples,which were extracted from the shoot tissue of rice seedlings,Sample-3 and Sample-4.In the peptides samples extracted from the root tissue of rice seedlings,RTLS24 h,RT-LS72 h,RT-HS24 h and RT-HS72 h,36,78,64,and 83 DEPs were identified respectively;In the peptides samples extracted from the shoot tissue of rice seedlings,STLS24 h,ST-LS72 h,ST-HS24 h and ST-HS72 h,19,51,6,and 23 DEPs were identified respectively.We did statistical analysis of the general characteristics of these DEPs,and compared their sequence with their precursor proteins’.We found the ladder-like distribution of peptides derived from the same precursor protein.Various characteristics of DEPs differed from sample to sample.The main source of peptides is that precursor proteins are hydrolyzed and cleaved at different sites under the action of proteolytic enzymes.These differences may be related to differences in the types and activities of proteolytic enzymes.2.Using phosphopeptidomics to extract phosphopeptides from rice seedlings that under 100 m M Na Cl treatment,4,4,46,15 non-redundant phosphopeptides were respectively identified in ST-CK,ST-NT,RT-CK and RT-NT.The basic characteristics of these phosphopeptides were analyzed and counted,and sequence comparisons were made with their precursor proteins.The unique ladder-like distribution of different peptides on the precursor protein was found,which may be related to the type and activity of proteolytic enzymes.3.Encoding genes of three peptide Os STPE1,Os STPE2,Os STPE3 were heterologous expressed in Arabidopsis.Among them,transgenic Arabidopsis lines with two peptide Os STPE2 and Os STPE3 have a significant increase in seed germination rate under high concentration of salt stress.This result preliminarily verifies our conjecture,and the molecular mechanisms involved in it is the goal of our next research and analysis.