Functional Analysis Of Transcription Factor StNAC78 In Cadmium Tolerance In Potato

NAC transcription factor(NAC transcription factor)is a member of plant family,which plays an important role in plant growth and development and stress.According to the previous transcriptome database analysis of Solanum tuberosum L,StNAC78 may be involved in regulating the expression of low cadmium accumulation genes in potato.Therefore,this study cloned StNAC78 gene from ’Weiyu 7’ and analyzed its bioinformatics and gene expression pattern,The phenotypic changes and physiological and biochemical indexes of transgenic tobacco(Nicotiana tabacum L)under cadmium stress were analyzed,and the function of the gene was preliminarily discussed,so as to provide theoretical basis for revealing the molecular mechanism of potato response to cadmium stress and breeding potato varieties with low cadmium accumulation.The main results are as follows:(1)StNAC78 gene was cloned from potato.The full length of its coding region was 1203 BP,encoding 400 amino acids with a molecular weight of 45.08 KD and a theoretical isoelectric point(PI)of 5.30.Sequence analysis showed that StNAC78 gene had no transmembrane domain and no signal peptide.Its secondary structure was mainly irregular curly structural elements.It was an unstable hydrophilic protein and had the closest genetic relationship with tomato and Solanum nigrum.(2)The expression pattern of StNAC78 gene under different heavy metal(Pb,Ni,Zn,Cu,CD)stress was analyzed by fluorescence quantitative analysis.The results showed that all the five heavy metals could induce the expression of StNAC78 gene,but the response modes of StNAC78 gene to the five heavy metals were different,and the expression levels of StNAC78 gene in roots,stems and leaves were different.The expression level of StNAC78 gene in roots under 12 h Ni stress was 13.79 times higher than that at 0 H;The expression levels of Pb and Zn in leaves at 12 h and 24 h were 3.72 and 6.31 times higher than those at 0 h,respectively;The expression of Cu and Cd in stem at 12 h was 3.85 times and 7.03 times higher than that at 0 h,and it was the most sensitive to Ni and Cd stress.(3)The plant expression vector pcambia1300-35s-StNAC78 was constructed and transformed into tobacco by Agrobacterium mediated transformation.Three transgenic lines with the highest expression and good growth were screened by QRT PCR for phenotype observation and physiological index determination after cadmium stress.The results showed that the growth of overexpression strain was better than that of wild type;The activities of peroxidase(POD),superoxide dismutase(SOD)and catalase(CAT)of transgenic(WT)lines were significantly higher than those of wild type;The content of malondialdehyde(MDA)was significantly lower than that of wild type(52%,58%,53%).It indicated that StNAC78 gene improved the tolerance of plants to cadmium stress.