Abstract
Insect female reproduction which comprises the synthesis of vitellogenein (Vg) in the fat body and its incorporation into developing oocytes, needs a large amount of energy and food resources. Our previous studies found that juvenile hormone (JH) regulates vitellogenesis in the brown planthopper, Nilaparvata lugens. Here, we report on the role of JH in nutrient-regulated Vg synthesis and egg development. We first cloned the genes coding for juvenile hormone acid methyltransferase (JHAMT) which is involved in JH biosynthesis and methoprene-tolerant (Met) for JH action. Amino acids (AAs) induced the expression of jmtN, while showing no effects on the expression of met using an artificial diet culture system. Reduction in JH biosynthesis or its action by RNA interference (RNAi)-mediated silencing of jmtN or met led to a severe inhibition of AAs-induced Vg synthesis and oocyte maturation, together with lower fecundity. Furthermore, exogenous application of JH III partially restored Vg expression levels in jmtN RNAi females. However, JH III application did not rescue Vg synthesis in these met RNAi insects. Our results show that AAs induce Vg synthesis in the fat body and egg development in concert with JH biosynthesis in Nilaparvata lugens (Stål), rather than through JH action.
Highlights
Nutrition and reproduction are important physiological processes in insects and nutrients have long been known to play key roles in the regulation of reproduction [1,2]
Using a newly developed artificial diet culture system, we found that nutrients (AAs) are necessary for the expression of jmtN which is involved in juvenile hormone (JH) biosynthesis [28,29]
Our results suggest that the JH pathway mediates amino acids (AAs)-induced Vg synthesis in the fat body playing an important role in ovarian growth and development
Summary
Nutrition and reproduction are important physiological processes in insects and nutrients have long been known to play key roles in the regulation of reproduction [1,2]. AAs derived from the blood meal have been demonstrated to be the key nutritional signals to stimulate Vg gene transcription and Vg protein synthesis in the fat body of mosquito [9,10,11]. In the starved beetles where genes coding for protein involved in JH biosynthesis (juvenile hormone acid methyltransferase, JHAMT) was disrupted by RNAi, Vg expression was severely inhibited even after feeding, suggesting that JH is indispensable for the nutrient-dependent Vg synthesis [12]. Our results suggest that the JH pathway mediates AAs-induced Vg synthesis in the fat body playing an important role in ovarian growth and development
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