Functional Analysis Of Receptor-Like Protein Kinase(RLK) In Cadmium Stress Response In Rice(Oryza Sativa L.)

In recent years,with the development of industry and agriculture,a large number of farmland has been polluted by cadmium?Cd?,posing a serious threat to the safety of plants and doing harm to human health through food chain.How to reduce the Cd content of rice has become an urgent front-burner.RLKs,a class of serine/threonine protein kinases,were known as important components that regulate plant development,hormone perception and stress response.In this paper,RLK overexpression transgenic rice plants?OE?,RNAi transgenic rice plants and wild-type rice plants?ZH11?were used as material to study the function of RLK in rice response to Cd stress.The main results were as follows:1.The bioinformatics and expression characteristics analysis of RLKBioinformatics prediction showed that RLK was a hydrophobic protein,localized in endoplasmic reticulum and plasma membrane,and had two transmembrane domains and one signal peptide;qRT-PCR was used to detect the expression of RLK in WT rice plants untreated with Cd.Results showed that during the seedling stage,tillering stage and panicle differentiation stage,RLK was mainly expressed in leaves.At the heading stage,filling stage and maturity stage,RLK was mainly expressed in panicle and node.2.The response of RLK overexpression and RNAi knockdown transgenic rice plants under Cd treatmentAfter 10 ?mol·L-L CdCl₂ stress for 2 W,OE rice plants had better growth compared to the WT rice plants,while Ri rice plants were more sensitive to Cd,which growth worse and had less chlorophyll.Both the increase of MDA and H₂O₂ were in order of Ri,WT and OE rice plants.The activities of POD,CAT and SOD were increased in OE rice plants,and were significantly reduced in Ri rice plants.These results indicated that overexpression of RLK could enhance the activity of antioxidant protective enzymes,alleviate the oxidative stress,so as to alleviate the toxic effect of Cd.3.The Cd accumulation characteristics of RLK overexpression and RNAi knockdown transgenic rice plantsAfter Cd stress,the contents of Cd in different parts?roots,stems,and leaves?and subcellular fractions were in order of Ri,WT and OE rice plants.The contents of Cd in different rice plants were in order of roots,stems and leaves.Results showed that Cd in roots was mainly concentrated in the cell wall,and Cd in overground part was concentrated in the cell wall and soluble fraction;The expression pattern of RLK as well as Cd accumulation and transport genes showed that overexpression of RLK could reduce the content of Cd in rice.OsNRAMP5,OsHMA2,OsHMA3,OsLCT1,OsLCD played roles in Cd accumulation and transport.RLK may affect the absorption and distribution of Cd by regulating the expression of those genes in rice.4.iTRAQ technique to screen the downstream genes of RLKUsing RLK RNAi knockdown transgenic and wild-type rice plants,a total of 289 proteins were identified by proteomic analysis of iTRAQ technique under Cd stress.It was suggested that RLK could regulate Cd tolerance through regulating the basic metabolism,stress response and redox state.The Peroxidase P7 gene was screened out by qRT-PCR,which may play a significant role in RLK regulating rice Cd tolerance.However,further research was needed to be done to validate its role.