Isolation And Molecular Characterzation Of HbWRKY 55 From Hevea Brasiliensis

Natural rubber(NR)is a cis-1,4-polyisoprene biopolymer that is highly valued because of its comparable elasticity,flexibility,and resistance to high temperature.The rubber tree(Hevea brasiliensis Muell.Arg)is still the only commercial source of NR mainly because of its abundance,quality,and ease of harvesting.WRKY proteins constitute a large family of transcription factors in plants.WRKY proteins are so named because of the highly conserved WRKY domain,which contains the almost invariant WRKYGQK sequence at the N-terminus.WRKY transcription factors are involved in many significant physiological and biochemical processes and have important roles in diverse biological processes in plants,such as the regulation of plant responses to abiotic stresses,plant hormone signaling,secondary metabolism.82 WRKY genes were identified in the latest rubber tree genome.However,little is known about the role of WRKY transcription factors in Hevea brasiliensis,especially the the regulatory mechanism of WRKY in NR biosynthesis.In this study,HbWRKY55 was able to interact specifically with the HbSRPP1 and HbHRT2 promoter to up-regulate its transcription in vivo,and HbWRKY55 promoter was analyzed and its function was preliminarily analyzed.The results will lay the foundation for a thorough understanding of the regulatory mechanism of WRKY in natural rubber biosynthesis.The main results are as follows:1.HbWRKY55 was expressed in all the tested tissues at different levels,with the highest transcription occurring in latex,followed by bark,leaves and flowers.The expression of HbWRKY55 was down-regulated by JA and SA,while ET up-regulated the expression of HbWRKY55.ABA exhibited little effect on the transcription of HbWRKY55 in the latex.2.HbWRKY55 was located in the nucleus.3.HbWRKY55 can bind to promoters of HbSRPP1 and HbHRT2 and activate the expression of HbSRPP1 and HbHRT2 promoter.It is speculated that HbWRKY55 may play a regulatory role in the synthesis process of NR.4.The HbWRKY55 promoter was cloned.Bioinformatics analysis showed that TATA box,CAAT-box and other core configurations were found in this promoter region.In addition several sequences similar to eukaryotic cis-regulatory such as gibberellin GARE-motif,P-box;salicylic acid response element TCA-element and other hormone response element were found in the promoter region.It was found that exogenous hormone GA and SA could inhibit the activity of HbWRKY55 promoter.