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Published on: July 14, 2023
How many times to molt? Endocrine control of moltinism in lepidopteran insects
1Department of Applied Biosciences, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan.
Abstract:
Although the endocrine regulation of insect molting and metamorphosis has been well characterized, the mechanisms that define how many larval molts occur before metamorphosis remain unclear. To examine the mechanisms that determine molt number, or moltinism, the silkworm Bombyx mori serves as a powerful model. Work with juvenile hormone-deficient mutants has shown that Bombyx larvae must complete at least two larval molts to acquire competence for metamorphosis, suggesting the presence of an unidentified factor that confers this competence. Furthermore, genetic analysis of the classic Moltinism locus revealed that the Hox gene Sex combs reduced (Scr) acts as a major regulator of molt number. Scr influences molting hormone biosynthesis and thereby governs the number of larval molts through the threshold size mechanism. Overall clarification of how insects set the number of molts will provide important insights into the evolution and the diversification of life histories in insects and other arthropods.
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