Proteomic And Physiological Responses To Salt(NaCl) Stress In Leymus Chinensis

Due to its strong salt resistance,Leymus chinensis is regarded as an important forage grass with economic and ecological value.Therefore,a deep study on salt-tolerant mechanism of L.chinensis will provide important theoretical basis and scientific basis for salt tolerant forage breeding.In this study,to reveal the initial salt tolerance mechanism,the effects of,L.chinensis seedlings were treated with different concentrations of NaCl,the growth and development,physiological indicators and differential proteins of L.chinensis in response to salt stress were analyzed.In order to reveal the regulatory mechanism of L.chinensis in response to salt stress,the effects of different salt stress concentration and time on the growth and development,chlorophyll,cell membrane,osmoregulatory substances and antioxidative enzyme activity were observed,and the differential proteomes were analyzed.The main contents include:the growth,physiological and biochemical mechanisms of L.chinensis under different salt stress,the abundance changes of differential proteins,and the identification and classification of the differential protein functions.The effect of salt stress on physiological parameters and proteome of L.chinensis was analyzed,and the regulatory mechanism of L.chinensis responding to salt stress was initially revealed.The results of this study are as follows:(1)The NaCl stress inhibited the growth of L.chinensis seedlings and the inhibitory effect became more obvious with the increase of stress intensity and stress time.(2)The determination of physiological and biochemical indexes of L.chinensis under salt stress revealed that:chlorophyll content of L.chinensis seedlings first increased and then decreased with the increase of stress intensity,and the chlorophyll content increased slightly with the increase of stress time.The relative electrical conductivity of L.chinensis seedlings increased with the increase of NaCl concentration and stress time.The contents of osmotic regulators(soluble sugars,soluble proteins,and free proline)increased first and then decreased with the increase of salt stress intensity,and increased slightly with the increase of stress time.The protective mechanisms of antioxidant enzymes were activated and the activities of POD,SOD and CAT in leaves all increased under NaCl stress.(3)A total of 10,858 unique peptides,3,814 proteins with quantitative information and274 differentially expressed proteins were selected in the leaves of L.chinensis using iTRAQ technology.The biological processes involved are mainly metabolic and cellular processes,the main functions performed are catalytic activity and binding proteins,the location of the cells is mainly cells and cell components,and the most important biochemical metabolic pathways and signal transduction pathways involved are amino acid biosynthesis and carbon metabolism.(4)Comprehensive analysis of the salt tolerance mechanism of L.chinensis:(1)Salt stress reduced the expression of chlorophyll synthesis precursor protein and key enzymes in the synthetic pathway and inhibited chlorophyll synthesis in L.chinensis.(2)Salt stress affects the expression of proteins involved in light reactions.On the one hand,it inhibits the FNR-mediated cyclic electron transfer(CET)response.On the other hand,it promotes transmembrane adverse transport of Na~+,and maintain the normal physiological function of the plant.(3)The down-regulation expression of related enzymes(C6YBD7,W5I7D1 and W5AFA2)in the Calvin cycle resulting affecting the carbon assimilation process,which inhibits the growth of the leaves and roots of L.chinensis.(4)L.chinensis responds to salt stress by regulating the expression of specific proteins in the citric acid cycle.Down-regulation of the key enzyme acetyltransferase(W5FJ50)in the citrate cycle under salt stress results in down-regulated expression of key enzymes in downstream processes(W5EKJ6,W5F8D5 and W5C6B8),which reduced the energy metabolism of plants.The key enzyme in proline biosynthesis may increase the proline synthesis ability and maintain cell osmotic balance.(5)The activities of antioxidant enzymes(SOD,POD and CAT),L.chinensis improved to scavenging ROS and reducing the effects of salt stress on organisms.(6)To maintain turgor pressure and cell structure stability,osmoprotectants(such as proline,soluble sugar and soluble protein)of L.chinensis accumulated under salt stress.And the up-regulation of the expression level in protein V-ATPase(W5BNG7)showed that more sodium ions accumulated in the vacuole to maintain the osmotic potential of the cell membrane under salt stress.The innovation of this research is as follows:(1)The innovation of the research is:using iTRAQ technology to find the differential proteome of L.chinensis under salt stress,and analyze the function and classification of differential proteins through bioinformatics.(2)The salt-tolerant mechanism of L.chinensis was analyzed from the Calvin cycle,citric acid cycle,chlorophyll synthesis and other biological pathways by observing the changes of growth,chlorophyll,cell membrane,penetration of L.chinensis under salt stress,combined with the analysis of differential protein expression.