Effects Of Low Temperature And Exogenous ABA On The Expressions Of ZmASR1 Gene In Maize Seedling

Maize(Zea mays L.)is one of the most important food crops in the world.It is a warmth-tolerant and short sunshine C4 crop,which requires higher temperature during the growth period.Low temperature,to a great extent,affects the yield and quality of maize,especially at seedling stage.Maize is highly sensitive to low temperature stress.As a kind of protein unique to plants,ASR()(abscisic acid,stress,ripening-induced)gene plays an important role in plant response to biological stress and abiotic stress.At present,ASR gene has been cloned from many plants.However,there are great differences in the degree of response of these ASR genes to stress.The study of ASR1 in maize at low temperature has not been reported at home and abroad,and the function expression of ASR1 in the process of maize cold resistance is still unclear.Therefore,it is of great significance to study the r esponse mechanism of ASR1 gene to low temperature stress in maize.In order to analyze the mechanism of Zm ASR1 stress tolerance,and to improve maize low temperature tolerance by genetic improvement in agricultural production.The experiment was conducted in the laboratory of maize cultivation physiology of Agricultural College of Northeast Agricultural University from 2014 to 2017.The main maize variety was ZD958,the low temperature tolerant maize inbred line Z58,and the low temperature sensitive maize inbred line C7-2,In the early stage of the experiment,seven maize gene sequences with similar sequence and unknown function were compared on NCBI,and the seedlings of ZD958 were treated under low temperature stress.The expression patterns of scene candidate genes under low temperature induction were analyzed by q PCR technique.Three high expression genes were screened out,and then the low temperature tolerant maize inbred line Z58 and the low temperature sensitive maize inbred line C7-2 were used as experimental materials under low temperature stress,exogenous ABA treatment and ABA+ low temperature stress,respectively.The expression patterns of three genes in roots,stems and leaves of maize seedlings were analyzed.The candidate gene Zm ASR1,with relatively high expression level and stable expression was screened.Agrobacterium tumefaciens transformation method was used to transform Arabidopsis thaliana(clo-0)and low temperature sensitive maize inbred line C7-2,Transgenic plants of Arabidopsis thaliana and maize Zm ASR1 were obtained and their functions were identified under different stress conditions.The main results are as follows.(1)Under low temperature,ABA,ABA+low temperature treatment the expression of Zm ASR1 in low temperature tolerant maize Z58 was higher than that in low temperature sensitive maize C7-2,and the expression of Zm ASR1 was up-regulated in root,stem and leaf,the expression level was higher than that in root > stem.Under low temperature stress,the expression of Zm ASR1 in the roots of maize seedlings reached the maximum at 48 h and reached the maximum at 24 h in stems and leaves,and Zm ASR1 began to express in the roots of maize seedlings induced by ABA.There was no significant difference between the interaction of ABA and low temperature on the expression of Zm ASR1 and the treatment of ABA alone,and there was no superimposed effect.(2)The overexpression of Zm ASR1 enhanced the chilling resistance of plants.Under low temperature stress,Zm ASR1-OE transgenic maize seedlings showed strong photosynthetic capacity,PSII maximum light energy conversion efficiency(Fv/Fm),photosynthetic rate(Pn),SPAD value higher than wild type;The activity of SOD,POD and CAT was higher than that of wild type,and the degree of membrane damage and lipid peroxidation was lower.The content of MDA,proline was higher than that of wild type,and the relative conductivity was lower than that of wild type.(3)Transgenic Arabidopsis thaliana with Zm ASR1 enhanced the cold resistance of the plants.Under low temperature stress,transgenic plants of Zm ASR1 Arabidopsis showed higher chlorophyll content,lower electrical conductivity and proline content than wild type plants,and had higher resistance to low temperature than wild type plants.(4)Spraying exogenous ABA,increased endogenous ABA content of maize seedlings,ABA content of Zm ASR1-OE transgenic seedlings was higher than that of wild type,and the ratio of ABA/GA?ABA/IAA was higher than that of wild type;Compared with wild type,the changes of endogenous hormones in Zm ASR1-OE transgenic seedlings enhanced the low temperature tolerance of plants.(5)Zm ASR1 over-expressed transgenic plants showed high sensitivity to ABA stress at germination stage,and ABA inhibited seed germination,and transpiration r ate and stomatal conductance at seedling stage were lower than those of wild type Arabidopsis,and decreased with the increase of ABA concentration.The over-expression of Zm ASR1 makes Arabidopsis exhibit a sensitive effect to ABA.(6)Zm ASR1 positively regulated the expression of stress-related genes.The expression of drought-inducible gene RD29 B,cold response gene COR15 A and RD29 A,salt and water stress-induced gene RD22,ROS clearance-related enzyme gene CAT3 in Arabidopsis transgenic with Zm ASR1 gene was up-regulated,and the antioxidant protective gene SOD4,CAT1,c APX in Zm ASR1-OE transgenic maize seedlings was up-regulated.