橡胶树HMGS编码基因的分离鉴定

Identification of HMGS-coding Genes from Hevea brasiliensis

羟甲基戊二酸单酰辅酶A合成酶(HMGS)将乙酰辅酶A转化为羟甲基戊二酸单酰辅酶A,是甲羟戊酸代谢途径的限速酶之一。本研究从橡胶树热研879和热研7-33-97品系的胶乳中分离出HbHMGS1和HbHMGS2基因。相比HbHMGS1基因在胶乳和树皮中的共表达模式,胶乳中高丰度表达的HbHMGS2基因可能是乳管细胞中参与天然橡胶合成的主效基因,而HbHMGS1是功能冗余基因。HbHMGS2基因在橡胶树高产品系热研879胶乳中的表达量亦高于测序品系热研7-33-97,表明HbHMGS2基因的高水平表达可能有助于橡胶的合成。其上游启动子的顺式作用元件差异可能与该基因在热研879和热研7-33-97的差异表达有关。HbHMGS2基因的转录亦受茉莉酸诱导,可能参与了茉莉酸信号调控天然橡胶的合成过程。HbHMGS2基因在大肠杆菌中成功表达为后续研究该基因的功能、利用该基因生产活性物质提供新的基因资源。

3-hydroxy-3-methylglutaryl coenzyme-A synthase is one of the rate-limiting enzymes in the mevalonate metabolic pathway via catalyzing the condensation of acetoacetyl-CoA to form 3-hydroxy-3-methylglutaryl-CoA. HbHMGS1 and HbHMGS2 genes were isolated from the latex of Reyan 879 and Reyan 7-33-97 rubber tree clones. When compared with the co-expression pattern of HbHMGS1 gene in the bark and latex, the HbHMGS2 gene especially expressed highly in the latex, suggesting it may be the main HMGS member gene involved in the natural rubber biosynthesis in laticifer cells, while the HbHMGS1 gene may be the redundant gene in rubber trees. The high expression level of HbHMGS2 gene in latex suggested it was beneficial for natural rubber biosynthesis, its differential expression pattern in Reyan 879 and Reyan 7-33-97 may be related to the differential cis-acting element located in the upstream promoters of the Reyan 879 and Reyan 7-33-97 HbHMGS2 genes. Its expression was induced by jasmonates, indicating that it may participate in the jasmonates signaling in regulating natural rubber biosynthesis process. The successful expression of HbHMGS2 gene in prokaryotic Escherichia coli after IPTG induction was not only laying the foundation for further investigating its roles in natural rubber biosynthesis, but also providing alternative gene resource for manufacture of bioactive products.