Identification And Charactcrization Of R2R3-MYB Transcription Factor And Their Response To The Abiotic Stress In Medicago Truncatula

Along with the deterioration of environment situation,the global plant production is suffering from serious threat of abiotic stress,such as cold stress,drought stress,salt stress and so on.It has become an important issue to be solved in plant genetic breeding field how to explore the stress resistance gene resources of plants.In recent years,studies have shown that transcription factors are widely involved in the process of plant growth and development,hormone regulation and response to abiotic stress,which makes it a hot topic in plant functional genomics researches.Medicago truncatula is an annual diploid plant of Legume Medicago.It has the advantages of small genome,self-pollination and high efficiency of genetic transformation,which enables it to rapidly become a model plant for leguminous research,especially in field of forage(alfalfa)genetics and breeding.With the completed of the genome sequencing of the Medicago truncatula,the researchers began to explore and identify the excellent gene function with Medicago truncatula genome so as to provide genetic resources for forage breeding.In this study,the genomic data of the Medicago truncatula,and the bioinformatics method were applied to explore and identify the members of the R2R3-MYB transcription factor family,one of the largest families of transcription factors.Besides,information of phylogenetic relationships and expression patterns of this gene family member are systematically analyzed to lay the foundation for its function.At the same time,abiotic stress transcriptome study of the Medicago truncatula was conducted to explore the excellent gene resources in Medicago truncatula related to the stress resistance.Finally,existing gene regulation information of Medicago truncatula was integrated to analyze gene regulation mechanism of R2R3-MYB transcription factor,and it was an important reference for further clarifying the function of these genes.The main findings can be seen as follows:1.Identification and charactcrization of R2R3-MYB transcription factor of Medicago truncatula.In this study,with double search method of the BLAST search and the domain search,150 R2R3-MYB transcription factor members were identified from the genome of Medicago truncatula.At the same time,gene structure and phylogenetic analysis of R2R3-MYB transcription factor of Medicago truncatula was completed by integrating known MYB transcription factor information of Arabidopsis thaliana and other plant species.Finally,the expression pattern of R2R3-MYB transcription factor members was determined with Medicago truncatula microarray data and transcriptome sequencing data in the common database,providing an important reference for clarifying their gene function.2.Sequencing study of abiotic stress transcriptome of Medicago truncatulaThe abiotic stress experiment on the Medicago truncatula was conducted,including six experimental groups(control group,cold stress,Freezing stress,osmotic stress,salt stress and ABA treatment stress),to carry out Abiotic stress transcriptome sequencing,and 135 million sequences were obtained.And by differential gene expression analysis,a total of 3360 differentially expressed genes were obtained,including low temperature stress,cold stress,osmotic stress,salt stress and ABA hormone.After the functional expression to these differential expression genes,it was found that they seem to be at enrichment in the annotated information related to abiotic stress,including transcriptional regulation of gene expression,redox reaction,and hormone response,which indicates that they may regulate the process of abiotic stress response of Medicago truncatula through these biological processes.Finally,10 R2R3-MYB transcription factors were selected for qRT-PCR expression test.The correlation between the results and transcriptome sequencing results was 0.85(average correlation coefficient),which indicated that the transcriptome sequencing result of this study was reliable..3.Investgation of molecular regulation mechanism of R2R3-MYB transcription factor in Medicago truncatula.Medicago truncatula gene regulation information was collected,and the Medicago truncatula gene control network was sort out and obtain.First,the gene regulatory network was analyzed to obtain the gene regulation module involving R2R3-MYB transcription factor.Then,the software topGO was used to analyze the function of gene regulatory module containing R2R3-MYB transcription factors,and the results showed that the functional genes of these gene regulatory modules were mainly in the process of abiotic stress response,redox reaction and photosynthetic metabolism,suggesting the Medicago truncatula R2R3-MYB transcription factor may regulate the growth and stress response of Medicago truncatula through these biological processes or metabolic ways,which is an important reference for further confirmation of its function.