Dusky-like is required for epidermal pigmentation and metamorphosis in Tribolium castaneum

Abstract

Dusky-like (Dyl) is associated with the morphogenesis of embryonic denticle, adult sensory bristle and wing hair in Drosophila melanogaster. And whether Dyl involved in insect post-embryonic development and its signal transduction are poorly understood. Here, phylogenetic analysis revealed that dyl displayed one-to-one orthologous relationship among insects. In Tribolium castaneum, dyl is abundantly expressed at the late embryonic stage. Tissue-specific expression analysis at the late adult stage illustrated high expression of dyl in the fat body and ovary. Knockdown of dyl resulted in the defects in larval epidermal pigmentation and completely blocked the transitions from larval to pupal and pupal to adult stages of T. castaneum. We further discovered that dyl RNAi phenotypes were phenocopied by blimp-1 or shavenbaby (svb) silencing, and dyl was positively regulated by blimp-1 through svb in T. castaneum. These results suggest that Dyl functions downstream of Blimp-1 through Svb for larval epidermal pigmentation and metamorphosis. Moreover, ftz-f1 was down-regulated after RNA interference (RNAi) suppressing any of those three genes, indicating that Ftz-f1 works downstream of Dyl to mediate the effects of Blimp-1, Svb and Dyl on metamorphosis in T. castaneum. This study provides valuable insights into functions and signaling pathway of insect Dyl.

Dusky works upstream of Four‐jointed and Forked in wing morphogenesis in Tribolium castaneum

“…The genes m (BeetleBase, accession number: TC003770), sn (BeetleBase, accession number: TC006673) and dyl (BeetleBase, accession number: TC001440) are also targets of svb in T. castaneum (Li et al ., ). Thus, we examined the expression levels of these genes in ds‐ dy insects.…”

“…At the transcriptional level, our ongoing experiments illustrated that wg knockdown down‐regulated svb and its target genes ( m , sn , f and dyl ) at the late larval stage in T. castaneum . Furthermore, knockdown or mutation of svb significantly decreased m , sn , f and dyl expression in T. castaneum (Li et al ., ) and D. melanogaster (Chanut‐Delalande et al ., ; Fernandes et al ., ). These results suggest that dy regulates svb and its target genes through wg in T. castaneum .…”

“…The wing gene network defined in D. melanogaster is largely conserved in T. castaneum (Tomoyasu et al ., ). This relationship is also observed between svb and dyl , f , sn and m in T. castaneum (Li et al ., ). However, whether dy , the homologue of dyl and m , is associated with wg and svb is unclear.…”

“…Mutation of either dy or m reduces the overall size of the wings by decreasing the size of individual wing epidermal cells but with milder effects than double mutation (Roch et al ., ), whereas dyl functions in the formation of embryonic denticles (Fernandes et al ., ), the deposition of cuticle during bristle development (Nagaraj & Adler, ), and the integrity and planar cell polarity of hairs during wing development (Adler et al ., ). These studies suggest that dy shares more functional similarities with m than with dyl , contrasting with the evolutionary relationship amongst these three genes in insects (Fernandes et al ., ; Li et al ., ). Recently, we reported that dyl is required for epidermal pigmentation and metamorphosis in Tribolium castaneum (Li et al ., ).…”

“…These studies suggest that dy shares more functional similarities with m than with dyl , contrasting with the evolutionary relationship amongst these three genes in insects (Fernandes et al ., ; Li et al ., ). Recently, we reported that dyl is required for epidermal pigmentation and metamorphosis in Tribolium castaneum (Li et al ., ). Whether evolutionary relationships amongst these three genes are consistent with their activities is difficult to clarify because the functions of dy and m have been reported only in D. melanogaster (Roch et al ., ).…”