Meeting Abstract
Molting in decapod crustaceans is controlled by ecdysteroid hormones synthesized and secreted by the molting gland, or Y-organ (YO). Halloween genes encode cytochrome P450 enzymes in the ecdysteroid synthetic pathway. The current paradigm is that YOs secrete inactive precursor (e.g., ecdysone), which is hydroxylated at the #20 carbon to active hormone (20E) by a cytochrome P450 20-hydroxylase in peripheral tissues. 20-Hydroxylase (CYP314A1) is encoded by Shed in decapods and Shade in insects. We used spiny lobster Shed sequences to extract and characterize orthologs in the G. lateralis YO transcriptome. Six contigs encoding Shed sequences were identified. Analysis of RNA-Seq data from animals induced to molt by multiple limb autotomy showed that Gl-Shed3 and Gl-Shed4 mRNA levels were highest in intermolt and lowest in postmolt animals. mRNA levels of Gl-Shed2 and Gl-Shed5 were highest in premolt and lowest in postmolt. Activin/Transforming growth factor beta (TGF&beta) signaling is responsible for transitioning the YO from activated state in early premolt to committed state in mid premolt. qPCR was used to quantify the effects of SB431542, an inhibitor of TGF&beta signaling, on mRNA levels in YO from control and experimental animals induced to molt by eyestalk ablation (ESA). ESA increased Gl-Shed5 mRNA level and decreased Gl-Shed6 mRNA level in control animals at 14 days post-ESA. SB431542 lowered Gl-Shed2 and Gl-Shed3 mRNA levels relative to those in controls at 14 days post-ESA, while SB431542 had no effect on Gl-Shed1, Gl-Shed4, Gl-Shed5, and Gl-Shed6 mRNA levels. Shed genes were expressed in all tissues examined. These data suggest that the YO is capable of secreting active ecdysteroid. Future work will determine whether the YO can synthesize and secrete 20E in vitro. Supported by NSF (IOS-1257732).
