Mechanism And Application On The Regulation Of MYB Transcription Factor To Stress Resistance In Hevea Brasiliensis

The growth and development of rubber tree(Hevea brasiliensis)were regulated by the biotic and abiotic stress,such as powdery mildew infection,wind,cold and drought stresses,etc.Powdery mildew(Oidium heveae Steinm.)is one of the most important leaf diseases in rubber tree.The plant MYB transcription factor family participates in the growth,differentiation,metabolism,biotic and abiotic stress responses,but the mechanism of the HbMYBs in the resistance to powdery mildew of the rubber tree remains to be elucidated.In this study,the molec?Lar biology,bioinformatics and plant pathology techniques were used to:1)comprehensively searching,identify,analyze and predict HbMYBs family members in the rubber leaf genome database;2)design qRT-PCR primers,analyze their expression patterns under the treatment of various tissues,ethylene and powdery mildew treatments;3)use the transgenic technology to prove HbMYB44 functions in stresses treatments in Arabidopsis,results were as follows:1.Using bioinformatics techniques,31 members of the HbMYBs family were identified,divided into 10 subgroups and characterized 4 unique motifs.The expression analysis found that the members of the HbMYBs family were mainly expressed in the flowers.The expression of 14 MYB family genes increased significantly in the powdery mildewinfected leaves.The expression of HbMYB44,HbMYB62 and HbMYB88 increased by 135,243 and 135 times,respectively.2.the HbMYB62 gene(GenBank:JQ 178240.1)was cloned by RT-PCR technique,with a sequence length of 1013 bp,including 945 bp ORF,which encodes 314 amino acids.Its deduced protein sequence contains the SANT-myb DNA binding domain of the plant MYB family.Real time quantitative PCR expression analysis showed that the expression of HbMYB62 was the highest in the flower,and the expression of HbMYB62 gene increased significantly at 48 h under drought and ABA treatment,respectively.The expression level of HhMYB62 increased significantly after mechanical wounding and H2O2 treatment,respectively.Under the treatment of ETH,SA,MeJA,IAA and other hormones,there is a significant difference in the expression of HbMYB62 at different time periods.3.The ORF of the HbMYB44 gene(GenBank:MG427050)was 1,038 bp,encoded 345 amino acids,The 34th-174th amino acid encoded the MYB domain.The cluster analysis showed that it was closely related to the Arabidopsis S22 family.The qRT-PCR analysis showed that the expression of HbMYB44 was the highest in the flowers,and the expression was significantly up to be expressed by ABA,ETH,JA hormone treatment and powdery mildew infection;subcellular localization analysis found HbMYB44 located in nucleus;yeast self activation verification found that HbMYB44 has the self activated activity and self activated region is located at the C end.After the overexpression of HbMYB44 in Arabidopsis,it was proved that transgenic Arabidopsis could significantly improve the resistance to drought stress and responsive to powdery mildew infection.The expression level of HbMYB44 gene in susceptible powdery mildew of rubber tree varieties is generally higher than that of resistance rubber tree varieties.4.This study lay a good foundation for elucidate the transcriptional regulation mechanism of HbMYB family members in the rubber tree resistance to powdery mildew,as well as apply the transgenic techniques to help the powdery mildew resistance breeding programs of rubber tree.