Regulation of cricket metamorphosis
Respective roles of Kr-h1, Br and E93 in hemimetabolous metamorphosis
友成, さゆり Tokushima University
Krüppel homolog 1
Juvenile hormones (JHs) and the genetic interaction between the transcription factors Krüppel homolog 1 (Kr-h1) and Broad (Br) regulate the transformation of insects from immature to adult forms in both types of metamorphosis (holometaboly with a pupal stage versus hemimetaboly with no pupal stage); however, knowledge about the exact instar in which this occurs is limited. Using the hemimetabolous cricket Gryllus bimaculatus (Gb), we demonstrate that a genetic interaction occurs among Gb’Kr-h1, Gb’Br and the adult-specifier transcription factor Gb’E93 from the sixth to final (eighth) nymphal instar. Gb’Kr-h1 and Gb’Br mRNAs were strongly expressed in the abdominal tissues of sixth instar nymphs, with precocious adult moults being induced by Gb’Kr-h1 or Gb’Br knockdown in the sixth instar. Depletion of Gb’Kr-h1 or Gb’Br up-regulates Gb’E93 in the sixth instar. In contrast, Gb’E93 knockdown at the sixth instar prevents nymphs transitioning to adults, instead producing supernumerary nymphs. Gb’E93 also represses Gb’Kr-h1 and Gb’Br expression in the penultimate nymphal instar, demonstrating its important role in adult differentiation. Our results suggest that the regulatory mechanisms underlying the pupal transition in holometabolous insects are evolutionarily conserved in hemimetabolous G. bimaculatus, with the penultimate and final nymphal periods being equivalent to the pupal stage.
Philosophical Transactions of the Royal Society B : Biological Sciences
The Royal Society
ptrsb_374_1783_20190225.pdf 1.99 MB