AUTHOR=Sun Ya-Ya , Fu Dan-Yang , Liu Bin , Wang Lin-Jun , Chen Hui 

TITLE=Roles of Krüppel Homolog 1 and Broad-Complex in the Development of Dendroctonus armandi (Coleoptera: Scolytinae)

JOURNAL=Frontiers in Physiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2022.865442

DOI=10.3389/fphys.2022.865442

ISSN=1664-042X

ABSTRACT=<p>In insects, metamorphosis is controlled by juvenile hormone (JH) and 20-hydroxyecdysone (20E). <italic>Krüppel homolog 1</italic> (<italic>Kr-h1</italic>), a key JH-early inducible gene, is responsible for the suppression of metamorphosis and the regulation of the <italic>Broad-Complex</italic> (<italic>Br-C</italic>) gene, which is induced by 20E and functions as a “pupal specifier”. In this study, we identified and characterized the expression patterns and tissue distribution of <italic>DaKr-h1</italic> and <italic>DaBr-C</italic> at various developmental stages of <italic>Dendroctonus armandi</italic>. The expression of the two genes was induced by JH analog (JHA) methoprene and 20E, and their functions were investigated by RNA interference. <italic>DaKr-h1</italic> and <italic>DaBr-C</italic> were predominantly expressed in the heads of larvae and were significantly downregulated during the molting stage. In contrast, the <italic>DaKr-h1</italic> transcript level was highest in the adult anterior midgut. <italic>DaBr-C</italic> was mainly expressed in female adults, with the highest transcript levels in the ovaries. In the larval and pupal stages, both JHA and 20E significantly induced <italic>DaKr-h1</italic>, but only 20E significantly induced <italic>DaBr-C</italic>, indicating the importance of hormones in metamorphosis. <italic>DaKr-h1</italic> knockdown in larvae upregulated <italic>DaBr-C</italic> expression, resulting in precocious metamorphosis from larvae to pupae and the formation of miniature pupae. <italic>DaKr-h1</italic> knockdown in pupae suppressed <italic>DaBr-C</italic> expression, increased emergence, caused abnormal morphology, and caused the formation of small-winged adults. These results suggest that <italic>DaKr-h1</italic> is required for the metamorphosis of <italic>D. armandi</italic>. Our findings provide insight into the roles of <italic>DaKr-h1</italic> and <italic>DaBr-C</italic> in JH-induced transcriptional repression and highlight <italic>DaKr-h1</italic> as a potential target for metamorphosis suppression in <italic>D. armandi</italic>.</p>