The silkworm homolog of Methoprene‐tolerant (Met) gene reveals sequence conservation but function divergence

Abstract

Abstract Methoprene‐tolerant (Met) gene has been found to be involved in juvenile hormone (JH) action in insects. Herein, we isolated a silkworm (Bombyx mori) homolog of Met gene from Drosophila melanogaster using bio‐informatics analysis and rapid amplification of cDNA ends – polymerase chain reaction method, and defined it as BmMet. The full‐length cDNA of BmMet gene consists of 1 917 nucleotides and includes a 1 368 bp of open reading frame for a deduced protein of 455 amino acids. All deduced protein sequences from Met genes in B. mori and other surveyed insects contain four typical domains of bHLH, PAS‐A, PAS‐B and PAC, highlighting a high sequence conservation of Met genes during insect evolution. Also, genomic structure and phylogenic analysis suggested that Met in both B. mori and Drosophila species may originate from an ancestor gene with gce, another member of bHLH‐PAS family, via gene duplication. In addition, BmMet was detected in all surveyed tissues and throughout the whole life of silkworm at transcriptional levels. Furthermore, silkworm individuals with RNAi silencing of BmMet gene in the early stage of the fourth instar larvae could molt normally and pupate successfully. This result was different from the observation in T. castaneum but similar to that in D. melanogaster after Met knockdown, revealing that the action mode of Met in B. mori and D. melanogaster should be divergent with that in other insect species.