Characterization of the Crustacean Methyl Farnesoate Transcriptional Signaling Genes

Methyl farnesoate (MF) is a sesquiterpenoid hormone that controls a variety of physiological processes in crustaceans, including morphogenesis, development, reproduction, and molting. MF action is mediated by a transcriptional signaling cascade consisting of <i>Methoprene-tolerant</i> (<i>Met</i>), <i>Steroid receptor coactivator</i> (<i>Src</i>), <i>Krüppel homolog 1</i> (<i>Kr-h1</i>), and <i>Ecdysone response gene 93</i> (<i>E93</i>) transcription factors (TFs), and transcriptional co-regulators <i>CREB-binding protein</i> (<i>CBP</i>) and <i>C-terminal-binding protein</i> (<i>CtBP</i>). Phylogenetic and sequence analyses revealed that these genes were highly conserved across pancrustacean species. Met and Src were characterized as basic helix-loop-helix, Period (Per)-Aryl Hydrocarbon Nuclear Translocator (ARNT)-Single-minded (Sim) protein (bHLH-PAS) TFs; Kr-h1 was characterized as a C₂H₂ zinc finger TF with seven zinc finger motifs; E93 was characterized as a helix-turn-helix, pipsqueak (HTH_Psq) TF. CBP was identified by several zinc finger-binding regions with Transcription Adaptor Zinc Finger 1 and 2, Really Interesting New Gene, Plant homeodomain, and Z-type zinc finger domains; the Kinase-inducible Domain Interacting-transcription factor docking site; the Bromodomain-acetylated lysine recognition and binding site; the histone acetyltransferase domain; and a C-terminal CREB-binding region containing a nuclear receptor co-activator-binding domain. CtBP had a dehydrogenase domain with arginine-glutamate-histidine catalytic triad. 81 <i>Met</i> contigs, 45 <i>Src</i> contigs, 136 <i>Kr-h1</i> contigs, 66 <i>E93</i> contigs, 60 <i>CBP</i> contigs, and 172 <i>CtBP</i> contigs were identified across pancrustacean taxa, including decapod crustaceans. Bioinformatic identification and annotation of these TFs and co-regulators in brachyuran Y-organ (YO) transcriptomes suggests that MF signaling influences YO ecdysteroidogenesis; functional tests in the YO are needed to establish causality.