SlNAC2 Enhanced The Stress Resistance Of Transgenic Arabidopsis And The Mechanism Analysis

NAC(NAM,ATAF1/2,CUC)transcription factors are plant specific transcription regulatory factors which not only participate in various growth and developmental process,but also respond to biotic and abiotic stress.Preliminary work in our laboratory has also cloned a NAC transcription factor from S.liaotungensis,named as SlNAC2,and obtained the seeds of second generation transgenic Arabidopsis.This study use seeds of second generation transgenic Arabidopsis as materious to screen the third generation of homozygous diploid Arabidopsis,and analyze abiotic stress resistance and mechanism of transgenic homozygous diploid Arabidopsis.The main results are as follows :1.T2 generation of transgenic plants were obtained in our previous research work.The transformants were selected on the MS culture medium containing Kanamycin,then obtained the pBI121-SlNAC2 transgenic Arabidopsis:L1 ? L2 ? L3 and pBI121-GUS transgenic Arabidopsis:VT1?VT2.Six strains of transgenic Arabidopsis were detected by RT-PCR,which demonstrate SlNAC2 was expressed in transgenic Arabidopsis.2.Under abiotic stress(drought,high salt,low temperature),morphological and physiological characteristics of transgenic Arabidopsis and wild Arabidopsis were analyzed.The morphological characteristics included survival rate,germination rate,root development,water content and stomatal aperture.The physiological characteristics includes chlorophyll fluorescence,soluble protein content,proline content,conductivity,and activity of antioxidant.Under abiotic stresses,the germination of these Arabidopsis thaliana were all restrained,but wild type and transgenic pBI121-GUS Arabidopsis thaliana was markedly.At the seeding growth stage,transgenic pBI121-SlNAC2 Arabidopsis were more tolerant than wild type and transgenic pBI121-GUS Arabidopsis thaliana on survival rate,root development,water content and stomatal aperture.The contents of proline and activity of antioxidant enzyme in the transgenic pBI121-SlNAC2 Arabidopsis were significantly higher than that in the wild type,and cell injury rates of transgenic plants was lower compared to the wild type and transgenic pBI121-GUS Arabidopsis.The results suggested that the expression of external gene SlNAC2 in transgenic Arabidopsis enhanced its resistance of abiotic stresses and reduced the damage caused by them.It is effectively proved that theSlNAC2 gene can enhance the ability of transgenic pBI121-SlNAC2 Arabidopsis thaliana resistance to abiotic stresses.3.The Agilent,s microarray was used to determine the differentially expression genes between wild and transgenic SlNAC2 Arabidopsis thaliana,and the expression patterns of selected differentially expressed genes were further identified by quantitative real-time PCR.The results showed that 1258 differentially expressed genes were screened out of transgenic SlNAC2 Arabidopsis thaliana,and showed that 706 genes were up-regulated,which22 genes were more than 50 times,522 genes were down-regulated.According to GO classification,the selected differentially expressed genes were related to development of plant cell growth and development,hormone signal transduction,enzyme regulator activity and the responses of plants to stress involved in a complex series of physiological and biochemical processes,such as ion transport,synthesis of antioxidants,interaction of transcription factors.Some different expression gene coded MYB?WRKY transcription factors and existed to the pathway in arginine and proline metabolism.SlNAC2 is one of family members of NAC transcription factors,which improved the transgenic Arabidopsis tolerance in abiotic stress through regulate of down-stream responsive genes.This study confirmed the SlNAC2 functions in abiotic stress,and revealed the regulation of downstream gene,which provides a new materials for the study of the mechanism of stress resistance in plants.