Requirement of Myoglianin for metamorphosis in the beetleHenosepilachna vigintioctopunctata

Abstract

Henosepilachna vigintioctopunctata is a serious defoliating beetle attacking Solanaceae and Cucurbitaceae plants in many Asian countries. In the present paper, we identified a putative myoglianin (myo) gene. Hvmyo was actively transcribed throughout development, from embryo to adult. RNA interference (RNAi)‐aided knockdown of Hvmyo delayed larval development by more than 2 days, reduced larval body size, inhibited the growth of antennae, wings and legs and disturbed gut purge. Knockdown of Hvmyo impaired the larval‐pupal transition. All the Hvmyo RNAi larvae arrested at the larval stage or formed misshapen pupae or adults. The deformed pupae and adults were partially wrapped with exuviae, bearing separated wings. Moreover, the expression levels of five ecdysteroidogenesis genes (Hvspo, Hvphm, Hvdib, Hvsad and Hvshd), a prothocicotropic hormone (PTTH)/Torso pathway gene (Hvtorso), two 20E receptor genes (HvEcR and HvUSP), and two 20E signalling genes (HvE93 and HvFTZ‐F1) were as a result of HvMyo RNAi significantly lowered. Conversely, the expression of a JH biosynthesis gene (Hvjhamt), a JH receptor gene HvMet and a JH signalling gene HvKr‐h1 was greatly enhanced. Although ingestion of 20E and Hal rescued the 20E signal, it could not alleviate larval performance and defective phenotypes. Our results suggest that Myo exerts four distinctive roles in ecdysteroidogenesis, JH production, organ growth and larva‐pupa‐adult transformation in H. vigintioctopunctata.

The Baboon Gene Encodes Three Functionally Distinct Transforming Growth Factor β Type I Receptor Variants in Henosepilachna vigintioctopunctata

“…These findings suggest that the three Babo isoforms redundantly control larval growth in H. vigintioctopunctata. This is the same with the observation that RNAi of Hvmyo results in small adult appendages [19]. Similarly, Drosophila babo-null mutants exhibit a significant reduction in the wing imaginal, wings, and escapers [12].…”

“…Given that two Activin ligands, Myo and Actβ, utilize BaboA activating downstream signaling molecules [7,10,14], an interesting question arises: Does (Do) either Myo or Actβ, or both, exert the regulatory role in the larval development in H. vigintioctopunctata? Notably, the defective phenotypes observed in HvbaboA (this study) and Hvsmox RNAi larvae [18] are more severe compared to those in Hvmyo knockdown alone beetles [19]. Based on this, we speculate that both Myo and Actβ play roles in larval development.…”

“…Likewise, overexpression of activated Babo in muscles enhances muscle size, leading to an enlarged Drosophila abdomen [30]. Collectively, these observations indicate that Activin signaling plays a pivotal role in the regulation of cell proliferation in H. vigintioctopunctata [19] and D. melanogaster [12,30,32].…”