The Number of Larval Molts Is Controlled by Hox in Caterpillars.

摘要: Animals with exoskeletons molt for further growth. In insects, the number of larval (or nymphal) molts varies inter- and intra-specifically, it is widely accepted that variation in an adaptive response to diverse environmental conditions.1-5 However, molecular mechanism underlies variety plasticity largely unknown. silkworm, Bombyx mori, there are strains three, four, or five times, these numbers determined by allelic at a single autosomal locus, Moltinism (M).6-9 Here, we demonstrate Hox gene Sex combs reduced (Scr) responsible phenotypes M locus. Scr selectively expressed prothoracic gland (PG), endocrine organ produces molting hormones.2Scr represses biosynthesis hormones PG, thereby regulating incremental increase body size during each instar. Our experiments consistently suggest differential expression levels among three alleles result different growth ratios ultimately lead molts. Although role genes conferring segmental identity along axis molding segment-specific structure later development has been well established,10-13 present study identifies unexpected hormone biosynthesis. This new means that, addition shaping morphology, also drive evolution life history traits animal physiology.