七星瓢虫卵黄原蛋白基因的表达mRNA的体外转译

七星瓢虫成熟雌虫脂肪体总RNA和poly(A)~+RNA中可转译mRNA的水平约为雄虫和不成熟雌虫的两倍,其中所含的卵黄原蛋白mRNA可在体外转译系统中指导卵黄原蛋白多肽的合成。 雌虫取食人工饲料时,其脂肪体RNA中可转译mRNA的水平很低,不能指导卵黄原蛋白多肽的合成。保幼激素类似物能诱导可转译卵黄原蛋白mRNA的出现。

EXPRESSION OF VITELLOGENIN GENE IN COCCINELLA SEPTEMPUNCTATA: IN VITRO TRANSLATION OF mRNA

Total fat body RNA and poly(A)+RNA were prepared from the lady beetle Coccinella septempunctata.Total protein synthesis directed by fat body RNA in the reticulocyte lysate system was linear for 90 min,and was proportional to the added RNA up to 600μg/ml reaction mixture under our standard conditions.The amount of translatable mRNA in different RNA preparations was assayed in the reticulocyte lysate system.The translatable mRNA in total fat body RNA and poly(A)+RNA from mature females was roughly twice as much as those in corresponding RNA preparations from immature females and males.Treatment with a juvenile hormone analogue ZR-512 doubled the amount of translatable mRNA in females reared on an artificial diet.Total fat body RNA from mature females and hormone-treated females directed the synthesis of larger vitellogenin(Vg) polypeptides in the reticulocyte lysate.Total RNA from immature females or males,however,failed to direct Vg synthesis in the cell-free system.Injection of total RNA or poly(A)+ RNA from mature females into Xenopus oocytes resulted in the synthesis of 4 Vg polypeptides which were immunologically and eletrophoretically indistinguishable from the Vg polypeptides synthesized and secreted by cultured fat body.RNA preparations from immature females and females on artificial diet did not direct Vg synthesis in Xenopus oocytes.Translation of RNA from those females after hormone treatment yielded 4 Vg polypeptides.Thus,the induction of Vg synthesis by juvenile hormone involves the increase in the level of translatable Vg mRNA in the lady beetle.