Cantharidin (CTD), a terpenoid defensive toxin mainly produced by blister beetles, is widely known by its toxicity to both cancer cells and pests. However, little information is known about its biosynthesis in blister...Cantharidin (CTD), a terpenoid defensive toxin mainly produced by blister beetles, is widely known by its toxicity to both cancer cells and pests. However, little information is known about its biosynthesis in blister beetles. In this study, first we determined the CTD content in various tissues of adult blister beetles on different days after mating, and then detected the temporal and spatial expression patterns of genes related to CTD biosynthesis in Epicauta chinensis. Results revealed that the accessory gland is the source of the highest CTD production. The second highest level was in the fat body in male blister beetles after mating. In females, the highest CTD content was in the reproductive system except the ovary after mating. As revealed by messenger RNA expression level analysis, the highest levels of 3-hydroxy-3-methylglutary-CoA reductase (HMGR) and juvenile hormone epoxide hydrolase (JHEH) transcripts of E. chinensis were observed in the fat body in males after mating. However, the highest transcript level of EcHMGR was in the ovary and EcJHEH was maintained at a nearly similar level in females. The transcript level of methyl-farnesoate epoxide was significantly higher in the head and that of CYP4BM1 in the midgut in both male and female E. chinensis. We speculate that the fat body may play a more important role than other tissues on the CTD biosynthesis in male E. chinensis after mating. There may be multiple tissues involved in the process of CTD biosynthesis. These four genes probably play regulatory roles in different tissues in males.展开更多
3-羟甲基戊二酰辅酶A-还原酶(3-hydroxy-3-methylglutaryl coenzyme A reductase,HMGR)是甲羟戊酸途径的关键酶。获得芫菁体内HMGR基因信息是确定甲羟戊酸途径与斑蝥素合成相关性的基础。本研究利用RACE技术从细纹豆芫菁Epicauta manner...3-羟甲基戊二酰辅酶A-还原酶(3-hydroxy-3-methylglutaryl coenzyme A reductase,HMGR)是甲羟戊酸途径的关键酶。获得芫菁体内HMGR基因信息是确定甲羟戊酸途径与斑蝥素合成相关性的基础。本研究利用RACE技术从细纹豆芫菁Epicauta mannerheimi(Mklin)体内克隆获得HMGR基因全长cDNA序列,命名为EmHMGR(GenBank登录号为JQ690539)。该基因全长3118bp,其中5'端非翻译区178bp,3'端非翻译区414bp,开放阅读框2526bp,编码842个氨基酸。推测的蛋白质分子量为92.8kDa,理论等电点为6.0,预测分子式为C4135H6604N1098O1216S50,不稳定系数为43.37,总亲水性系数为0.091,为疏水性不稳定蛋白。序列分析发现该基因编码的蛋白与已报道的其他昆虫HMGR的氨基酸序列一致性达50%以上,而且包含HMGR_Class I保守功能域、固醇敏感多肽区及HMGR蛋白的其他保守功能位点。系统进化分析发现该基因与叶甲科昆虫HMGR基因的关系最近。本研究首次从芫菁科昆虫体内克隆获得甲羟戊酸途径的关键酶EmHMGR基因,为后期芫菁体内斑蝥素生物合成途径的研究奠定了基础。展开更多
基金the Special Fund for the Public Interest (Agriculture)(Grant No. 200903052)the "113115" Sci-Tech Innovation Project of Shaanxi Province (No. 2007ZDKG-14 and No. 2009ZDKG-06), the National Natural Science Foundation of China (No. 31101442)the Fundamental Research Funds for the Central Universities (No. 2452015113 and No. 2452013QN044).
文摘Cantharidin (CTD), a terpenoid defensive toxin mainly produced by blister beetles, is widely known by its toxicity to both cancer cells and pests. However, little information is known about its biosynthesis in blister beetles. In this study, first we determined the CTD content in various tissues of adult blister beetles on different days after mating, and then detected the temporal and spatial expression patterns of genes related to CTD biosynthesis in Epicauta chinensis. Results revealed that the accessory gland is the source of the highest CTD production. The second highest level was in the fat body in male blister beetles after mating. In females, the highest CTD content was in the reproductive system except the ovary after mating. As revealed by messenger RNA expression level analysis, the highest levels of 3-hydroxy-3-methylglutary-CoA reductase (HMGR) and juvenile hormone epoxide hydrolase (JHEH) transcripts of E. chinensis were observed in the fat body in males after mating. However, the highest transcript level of EcHMGR was in the ovary and EcJHEH was maintained at a nearly similar level in females. The transcript level of methyl-farnesoate epoxide was significantly higher in the head and that of CYP4BM1 in the midgut in both male and female E. chinensis. We speculate that the fat body may play a more important role than other tissues on the CTD biosynthesis in male E. chinensis after mating. There may be multiple tissues involved in the process of CTD biosynthesis. These four genes probably play regulatory roles in different tissues in males.
