Genome Identification And Expression Analysis Of BdGRAS Family Gene In Brachypodium Distachyon

The GRAS family is an important transcription factor family in plants.It was first discovered in Arabidopsis thaliana and named after its first three members,namely gibberellic acid insensitive(GAI)、repressor of GA1-3 mutant(RGA)and scarecrow(SCR).At present,GRAS family genes have been reported in a variety of plants,and it has been proved that the GRAS family is involved in plant growth and development regulation,disease resistance and stress resistance,and hormone signal transduction pathways.Brachypodium distachyon is a new model plant of the Gramineae family.It has the characteristics of short growth cycle,small plants,low requirements for growth environment,small genome,easy genetic transformation and infection of rice blast fungus.In this study,the BdGRAS family genes of B.distachyon were identified and expressed in order to promote the study of molecular interaction between rice and rice blast fungus.The main results are as follows:1.A total of 63 BdGRAS protein sequences were retrieved from the plant transcription factor database,and the GRAS family protein sequences of rice and Arabidopsis were also obtained.The phylogenetic tree analysis was performed using MEGA7.0.The results showed that the BdGRAS family was divided into 10 subfamilies.Most BdGRAS proteins、Os GRAS proteins and At GRAS proteins belong to the same clade as,indicating that they have a certain degree of homology in the evolutionary relationship.2.The genes of the BdGRAS family of B.distachyon are unevenly distributed on 5chromosomes.Among them,chromosome 4 is the most distributed with 28,and chromosome 5 is the least distributed with only 3.There are 5 pairs of tandem repeat genes in the BdGRAS family,indicating that B.distachyon may have undergone genome replication events during the evolution process.3.The BdGRAS family of B.distachyon contains the typical GRAS domain,GRAS superfamily domain,DELLA and PA28-alpha superfamily,which have a highly conserved domain at the C-terminus and highly variable at the N-terminus.At the same time,20 motifs structures have been identified for BdGRAS family proteins,which have a certain influence on the function of BdGRAS protein.4.Tissue-specific expression pattern analysis of BdGRAS gene was conducted by semi-quantitative method,and it was found that most BdGRAS genes were expressed in roots,stems,leaves,and seeds,indicating that BdGRAS family genes regulate the growth and development of B.distachyon.5.After 1 h the treatment with different hormones(SA,JA,IAA,ABA)of B.distachyon seedlings,the transcription level of BdGRAS34,BdGRAS36,BdGRAS37,BdGRAS38,BdGRAS39,BdGRAS40,BdGRAS41,BdGRAS42 and BdGRAS45 genes decreased,and the expression levels of the other genes were different.It indicates that BdGRAS family genes regulate hormones signal transduction pathway.6.The expression of most BdGRAS genes was significantly increased after B.distachyon was inoculated with rice blast fungus RO1-1.At the same time,this study also identified BdGRAS31 as the target gene of mi R171 related to disease resistance,indicates that BdGRAS31 is regulated by Bd-mi R171 and participates in the resistance of B.distachyon to rice blast.7.The transcriptional activity of BdGRAS protein was verified by yeast self-activation,and nine BdGRAS protein transcriptional activities were tested,of which eight had transcriptional activation activity,and only one had transcriptional inhibitory activity,indicating that most of Bd GARS proteins have transcriptional activity and regulate target genes through a variety of ways.