College of Forestry, Shandong Agricultural University, Taian, Shandong, China.
School of Biology and Basic Medical Sciences, Medical College, Soochow University, Suzhou, China.
Arch Insect Biochem Physiol. 2021 Apr;106(4):e21783. doi: 10.1002/arch.21783. Epub 2021 Mar 15.
Vitamin C (VC) is an essential nutrient for many animals. However, whether insects, including Bombyx mori, can synthesize VC remains unclear. In this article, the optimized HPLC method was used to determine the content of l-ascorbic acid (AsA) in silkworm eggs, larvae and pupae, and the activity of l-gulono-1,4-lactone oxidase (GULO), a key enzyme in VC synthesis. The RNA interference method was used to determine the effect of the BmGulo-like gene on embryonic development and GULO activity in the pupal fat body. The AsA content increased significantly during E144 h-E168 h in the late embryonic stage and P48 h-P144 h in the middle-late pupal stage, in which exogenous VC was not ingested. Furthermore, the body AsA content in larvae fed VC-free feed also increased with larval stage. The GULO enzymatic activity was present in eggs and the fat bodies of larvae and pupae, even when the larvae were reared with fresh mulberry leaves. Moreover, the activity was higher in the later embryonic stages (E144 h-E168 h) and the early pupal stage (before P24 h). The GULO activity in the pupal fat body dramatically decreased when the screened BmGulo-like gene (BGIBMGA005735) was knocked down with small interfering RNA; in addition, the survival rate and hatching rate of eggs significantly decreased 21% and 44%, respectively, and embryonic development was delayed. Thus, Bombyx mori can synthesize AsA through the l-gulose pathway, albeit with low activity, and this synthesis ability varies with developmental stages.
维生素 C（VC）是许多动物必需的营养物质。然而，昆虫是否能合成 VC 仍不清楚，包括家蚕。在本文中，我们使用优化的 HPLC 方法测定了家蚕卵、幼虫和蛹中 l-抗坏血酸（AsA）的含量以及 VC 合成关键酶 l-古洛糖酸-1,4-内酯氧化酶（GULO）的活性。利用 RNA 干扰方法确定了 BmGulo-like 基因对蛹期脂肪体胚胎发育和 GULO 活性的影响。在胚胎晚期的 E144 h-E168 h 和中晚期蛹期的 P48 h-P144 h 期间，AsA 含量显著增加，在此期间未摄取外源性 VC。此外，饲喂无 VC 饲料的幼虫的体内 AsA 含量也随幼虫期的增加而增加。卵中和幼虫和蛹的脂肪体中均存在 GULO 酶活性，即使幼虫以新鲜桑叶饲养也是如此。此外，活性在胚胎后期（E144 h-E168 h）和早期蛹期（P24 h 之前）更高。用小干扰 RNA 敲低筛选出的 BmGulo-like 基因（BGIBMGA005735）后，蛹期脂肪体中的 GULO 活性显著降低；此外，卵的存活率和孵化率分别显著降低了 21%和 44%，并且胚胎发育延迟。因此，家蚕可以通过 l-古洛酮酸途径合成 AsA，尽管活性较低，但这种合成能力随发育阶段而变化。
