Cloning And Functional Analysis Of Soybean MYC Transcription Factor

Plants will meet some kinds of stresses inevitably in the period of growing life.for example,the low or high temperatures、drought、salt、insect pest and so on.Crop growth of plants affected by the pest seriously,particularly for the development of agricultural and quality of production.It was a threat to economic cost to human.Transcription factors play an important role in the plant response to stresses. Signal transduction pathways in the plants transcription factors has been shown to bind revelant to element and activate resistance gene expression.In this study we characterized genes by meas of in silico cloning.Nucleotide sequence of A tMYC2 was used as a querying probe to screen EST database of Glycine max and the candidate ESTs was contigging.the extension of genes from genomic library of Glycine max.we made the gene-specific primers,seven full-length cDNAs sequences of Glycine max were confirmed by amplifying cDNA of Glycine max. cv huan pi xiao qing dou. The phylogenetic tree based on amino acid sequences of GmMYCs genes.The result showed that GmMYC5 and GmMYC6 were clustered into one branch; GmMYC3 and GmMYC7 were clustered into one branch; GmMYC1 and GmMYC4 were clustered into one branch; GmMYC2 was the only branch. The protein of the GmMYCs genes have a typical DNA binding domain:basic/helix-loop-helix(bHLH) motif at the C-terminus. It was reported that MYC transcription factors play a key role in multiple biological functions and responses to stresses such as jasmonate signaling in plant.To investigate the expression pattern of GmMYCs in Glycine max,the expression of the seven genes at different organs was analyzed.in root、stem and leaves these genes were highly expression,but with no expression in seed almost by real-time fluorescence quantitative PCR technique.The expression levels of GmMYCs were different in several stresses.Under cotton worms,the expression levels of GmMYCs were the highliest.The transcriptional activation assay showed that GmMYCs encoding products had the transcriptional activation activities in yeast. To further examine the effect of GmMYCs genes, it was overexpressed in tobacco.Insect bioassay was performed to test the insecticidal activity of the GmMYCs overexpressed in transgenic tobacco plants.Dual-choice feeding preference test showed that cottom worms chosed to eat control leaves were more than transgenic tobacco leaves, and control tobacco leaves were more significantly damaged compared to transgenic,PI<1. during force-fed experiment after 24 hours control tobacco leaves consumed were lager significantly than transgenic.The size and RGR of cottom worms feeding control leaves were larger than those fed by transgenic tobacco leaves. The results reveal the importance of GmMYC1and GmMYC5 in defense insect affected.consequence,GmMYC1and GmMYC5 genes may be a useful tool for improving resistance against insect in Glycine max.