Abdominal‐B regulates structure and development of the Harmonia axyridis cremaster

Abstract

The ladybird Harmonia axyridis is an insect that exhibits pupal attachment to plants, which facilitates development and environmental adaptation. The cremaster is highly specialized for this behavior. However, the underlying molecular regulation of the cremaster remains unclear; therefore, we performed experiments to investigate the transcriptional regulation of cremaster development. First, we examined the morphological structure of the cremaster to reveal its function in pupal attachment of H. axyridis. Next, we analyzed the Hox gene Ha-Abd-B using RNA interference (RNAi) to determine its function in regulating cremaster formation; Ha-Abd-B up-regulation promoted effective pupal attachment, whereas successful RNAi caused severe down-regulation of this gene, and pupae were unable to attach. Furthermore, successful RNAi and subsequent Ha-Abd-B down-regulation caused phenotypic changes in cremaster structure, including its complete disappearance from some individuals. Finally, we observed unique development of the cremaster and dynamic expression of Ha-Abd-B during pre-pupal development; consequently, we hypothesized that there was specific pre-pupal development of the cremaster. Overall, based on these results, the specialized cremasteric structure located on the posterior side of H. axyridis was determined to be a key organ for pupal attachment. Cremaster identification in H. axyridis is regulated by Ha-Abd-B and exhibits preferential development. Pupal attachment of H. axyridis reveals an environmental adaptation of this species; thus, this study and future molecular studies will help determine the role of Hox genes in regulation of insect attachment and further our understanding of the multiple functions of Hox genes.

Functional characterization of developmentally critical genes in the white‐backed planthopper: Efficacy of nanoparticle‐based dsRNA sprays for pest control

“…93,[95][96][97] Furthermore, inhibition of Abd-B expression has been reported to have drastic morphological effects, including transforming ovipositors into legs or antennae 65,[72][73][74] and the development of prolegs on segments A7-A9 to develop, indicating that Abd-B is critical for restraining appendage development in the posterior abdominal segments. 75,[98][99][100] Our data showed that RNAi-induced knockdown of SfAbd-B in females caused a genitalia-to-leg transformation in addition to replacing the first and second valvulae on the ovipositors with one pair of protruding appendages. SfAbd-B RNAi also resulted in stunted posterior abdominal segments and failed wing expansion, suggesting SfAbd-B is essential for their normal development in WBPH.…”

The Hox gene Abdominal‐B regulates the appendage development during the embryogenesis of scorpionflies

“…Abd-B plays a key role in regulating cremaster (a specialized tail organ) development during the pre-pupal stage of the ladybird beetle Harmonia axyridis(Zhang et al, 2020). In our present study, the annulatedF I G U R E 6 Different levels of larval phenotypic changes resulted from Abd-Bs RNAi.…”

“…A similar phenotype is visible in Tribolium larvae and Oncopeltus hatchlings, wherein reduction of Abd‐B activity transforms abdominal segments to adopt a more anterior identity and leads to ectopic terminal structures (Angelini & Kaufman, 2005; Beeman et al, 1989; Wool & Medlinger, 1973). A recent study revealed that Abd‐B plays a key role in regulating cremaster (a specialized tail organ) development during the pre‐pupal stage of the ladybird beetle Harmonia axyridis (Zhang et al, 2020). In our present study, the annulated processes on A8 are abnormally‐shaped after ds Abd‐B injection, like those normally seen between the more anterior segments, suggesting a transformation to a more anterior abdominal identity.…”

“…Abdominal‐B ( Abd‐B ) is a posterior Hox gene of BX‐C and generates morphological diversity along the posterior segments of the abdomen by controlling complex developmental processes (Damen & Tautz, 1999; Foret & Maleszka, 2006; Jin et al, 2019; Kuziora & McGinnis, 1988). In the fruit fly D. melanogaster (Diptera) and the flour beetle Tribolium castaneum (Coleoptera), Abd‐B suppresses embryonic appendage development via repressing Distal‐less ( Dll , a limb‐promoting gene) expression in the abdominal segments, and specifies posterior spiracle development and terminal structures during the pupal stage (Beeman et al, 1989; Lewis, 1978; Pinto et al, 2015; Vachon et al, 1992; Zhang et al, 2020). In some insects, Abd‐B is required in the abdominal segments and the genitalia, because the absence of Abd‐B transforms posterior abdominal segments into more anterior ones (Angelini & Kaufman, 2005; Coutelis et al, 2013; Estrada & Sánchez‐Herrero, 2001; Foronda et al, 2015; Kelsh et al, 1993; Stansbury & Moczek, 2014).…”

Homeodomain proteins POU‐M2, antennapedia and abdominal‐B are involved in regulation of the segment‐specific expression of the clip‐domain serine protease gene CLIP13 in the silkworm, Bombyx mori

“…Antp was shown to play an important role in determining normal thoracic segments during body development of D. melanogaster and B. mori (Rosenfield & Ziff, 2006;Chen et al, 2013). Abd-B was involved in developmental regulation of testis cell identity, body pigmentation, the central nervous system and cremaster in insects (Zhang et al, 2017;Jin et al, 2019;Ghosh et al, 2019;Zhang et al, 2020). Abd-B also suppressed proleg development in posterior abdominal segments in B. mori (Tomita & Kikuchi, 2009).…”