家蚕有色茧主要色素物质在幼虫体内的代谢变化

为探讨有色茧色素物质在蚕体内的代谢机制,检测了有色茧主要色素物质的含量及其在家蚕5龄幼虫不同时期中肠、血液、丝腺组织中的消长变化,分析色素物质从中肠进入血液再转运到丝腺的时序差异。有色茧中,黄茧的色素以类胡萝卜素化合物为主,绿茧的色素以黄酮类化合物为主。黄酮类化合物、类胡萝卜素化合物在家蚕5龄幼虫中肠、血液、中部丝腺、后部丝腺中的含量均呈现龄初低、龄末高的趋势,其中,黄酮类化合物在熟蚕组织中的含量是中肠>血液>中部丝腺>后部丝腺;类胡萝卜素化合物在熟蚕组织中的含量是中部丝腺>后部丝腺>中肠>血液。2种色素物质含量变幅最大的是后部丝腺组织,结黄茧蚕和结绿茧蚕的黄酮类化合物分别增加406.55%、202.50%,类胡萝卜素化合物分别增加211.80%、250.84%。黄酮类化合物在5龄幼虫丝腺组织的绝对含量是结绿茧蚕大于结黄茧蚕,类胡萝卜素化合物在5龄幼虫丝腺组织的绝对含量是结黄茧蚕显著大于结绿茧蚕,与在不同颜色蚕茧中检测到的2种色素物质含量一致。研究结果提示:黄酮类化合物在5龄幼虫中肠组织中积累较多,类胡萝卜素化合物在丝腺组织中积累较多;丝腺组织中2种色素物质的含量与茧色密切相关;来自桑叶中的2种色素物质经中肠消化吸收后,再通过血液进入丝腺组织并产生累积效应。

Metabolic Variations of the Main Pigment Substances in Silkworm Larvae Spinning Colored Cocoons

In order to explore the metabolic mechanism of pigment substance of colored cocoon in larval body of the silk-worm (Bombyx mori),the contents of the main pigment substances in the colored cocoons and the growth and decline changes of flavonoids and carotenoids in the midgut,hemolymph and silk gland of the 5th instar larvae were detected, and the timing differences of pigment substance transportation from midgut into hemolymph and then into silk gland were analyzed.It was found that carotenoids and flavonoids were the major pigment substances in yellow and green cocoons, respectively.The contents of flavonoids and carotenoids in midgut,hemolymph,middle silk gland and posterior silk gland of the 5th instar larvae were all lower at the beginning of the instar than those at the end of the instar.The content of flavonoids in mature larval tissues was in the order of midgut > hemolymph > middle silk gland > posterior silk gland.The content of carotenoids in mature larval tissues was in the order of middle silk gland > posterior silk gland > midgut >hemolymph.The amplitude of content changes of both pigment substances was the highest in posterior silk gland:the flavonoids in larvae spinning yellow cocoons and green cocoons were increased by 406.55% and 202.50% respectively, and the carotenoids in larvae spinning yellow cocoons and green cocoons were increased by 211.80% and 250.84%,respectively.The absolute content of flavonoids in silk gland of the 5th instar larvae spinning green cocoons was higher than that of yellow cocoons,and that of carotenoids in silk gland of the 5th instar larvae spinning yellow cocoons was significantly higher than that of green cocoons,being consistent with the contents of both pigment substances detected in the colored co-coons.The above results suggest that flavonoids were mainly accumulated in midgut and carotenoids were mainly accumulated in silk gland of the 5th instar larvae.The contents of both pigment substances in silk gland are closely related with cocoon color.After the two pigment substances from mulberry leaves are digested and absorbed in midgut,they are transported into silk gland tissue by hemolymph and are then accumulated there.