Meeting Abstract
Molting is necessary for growth and development in all arthropods. Halloween genes are expressed in the molting gland (Y-organ or YO) and encode enzymes that catalyze the synthesis of ecdysteroid hormones that coordinate molting processes during the premolt stage. The YO transitions through four physiological states over the molt cycle: basal (intermolt), activated (early premolt), committed (mid to late premolt), and repressed (postmolt). mTOR activity is required for YO activation and TGFβ/Activin signaling mediates YO commitment. Contigs encoding six of ecdysteroidogenic genes (neverland, phantom, disembodied, spook, shadow, and Cyp18a1) were identified in the YO transcriptome. Sequences were validated by Sanger sequencing of PCR products. RNA-Seq data showed that relative mRNA levels of Halloween genes were highest in intermolt and early premolt and then decreased during mid and late premolt to their lowest levels 10 days postmolt. Ecdysteroid receptor (EcR/RXR) binds active molting hormone, which induces serial activation of ecdysone-responsive genes. Insect gene sequences were used to extract seven orthologs from the land crab YO transcriptome: Broad Complex, E75, E74, Hormone Receptor 4, Hormone Receptor 3, forkhead box transcription factor, and Fushi tarazu factor-1. The presence of EcR/RXR and ecdysone-responsive genes suggest that elevated ecdysteroid represses the YO at the end of premolt. Using RNA-Seq and qPCR, we will quantify the effects of molting, mTOR inhibitor (rapamycin), and Activin receptor antagonist (SB431542) on gene expression. Supported by NSF (IOS-1257732).
