Studies On The Transcriptional Regulation Of Key Enzymes Of Natural Rubber Biosynthesis By MYC And Myb Transcription Factors

As one of the world’s four big industrial raw materials, rubber is an important strategic material. At present, more than99%of natural rubber obtained from rubber tree (Hevea brasiliensis). Laticifers are specific for rubber biosynthesis and storage. The natural rubber biosynthesis is a kind of typical isoprenoids metabolism of plants. The number of laticifer cell in tree bark, latex regeneration between two tappings, and duration of latex flow are the three key factors that determine the natural rubber yield. These three factors are both genetic characteristics of rubber tree clone and significantly affected by environmental conditions. Studies have shown that jasmonic acid is the key signaling molecule regulating laticifer differentiation, and rubber biosynthesis is mainly regulated by jasmonic acid signaling pathway. Researches on the molecular mechanisms of jasmonic acid signal pathway show that members of MYC transcription factors family is important for regulating jasmonic acid-responsive functional genes. Although available evidence shows that members of MYC transcriptional factor family are involved in the regulation of rubber biosynthesis, little is known about the interaction of MYC members as well as their interaction with other ranscription factor familymembers on the regulation of key enzymes for natural rubber biosynthesis. In this study, six transcription factors were identified to regulated some key enzymes of rubber biosynthesis by means of yeast one hybrid, quantit-ative PCR, yeast two hybrid technology, and related molecular biological technique. The main results were as follows:1, By using bioinformatics technology, four new MYC members were founded from rubber latex transcriptome library, and their full length CDS were cloned and designated as Hb1MYC6, Hb1MYC7, Hb1MYC8, Hb1MYC9, respectively. Bioinformatics analysis indicated that all of them have no introns, but contain two conservative domain, bHLHMYC-N and HLH, suggesting that they, belong to the MYC transcriptional favtor family. The Hb1MYC6and Hb1MYC7share54.78%and54.78%homology of AtMYC2, respectively.2, The length of the cloned promoter of HMGR1, HMGS1, HRT1, HRT2, REF, SRPP was1501bp,1100bp,1461bp,1500bp,1500bp,1159bp, respectively.3, Point-to-point yeast one hybrid analysis showed that Hb1MYC1, Hb1MYC3, H1MYC7have binding activity with G-box components in the genes encoding rubber biosynthesis key enzyme REF and SRPP; Hb1MYC7have binding activity with G-box component in the gene encoding key enzyme of rubber biosynthesis HMGR.4, Point-to-point yeast two hybrid analysis showed the physical interaction between Hb1MYC1and Hb1MYC1,between Hb1MYC1and Hb1MYC3, between HbMyb1and Hb1MYC1, and between HbMybl and HbMybl. But there is no physical interaction between Hb1MYC3and Hb1MYC6or HbMybl.5, Coronatine is effective on upregulating the expression of genes encoding HRT1, HMGR1,SRPP, and REF.