Expression patterns of MIH, EcR2, and RXR3 in the moult cycle of the red swamp crayfish, Procambarus clarkii (Girard, 1852) (Decapoda, Cambaridae)

Abstract

In arthropods, the moult-inhibiting hormone (MIH), the ecdysone receptor (EcR), and the retinoid X receptor (RXR) are key regulators in moulting. In the present study, the full-length cDNAs of the MIH, EcR2, and RXR3 genes from the red swamp crayfish, Procambarus clarkii (Girard, 1852) (denoted as PcMIH, PcEcR2, and PcRXR3) were cloned. Tissue-specific and moult stage-specific mRNA expression patterns of these genes were detected by real-time quantitative polymerase chain reaction. PcMIH was detected only in the eyestalk, whereas PcEcR2 and PcRXR3 mRNA were expressed in all tissues tested. The highest levels of PcEcR2 and PcRXR3 were detected in the gill and hepatopancreas. Expression of PcMIH mRNA in the eyestalk increased from postmoult to peak in intermoult and then decreased in premoult. Expression of PcEcR2 mRNA in the eyestalk, hepatopancreas, and muscle increased from postmoult to peak in early premoult and then decreased. However, expression of PcEcR2 mRNA in the gill increased from postmoult to reach a maximum in intermoult and then decreased in premoult. Expression of PcRXR3 mRNA also fluctuated in the eyestalk, hepatopancreas, muscle, and gill, with a decrease from postmoult to late premoult. Expression of PcEcR2 and PcRXR3 mRNA increased relative to the control in the hepatopancreas and gill after unilateral and bilateral eyestalk ablation, which suggested that PcMIH can inhibit their mRNA expression. Double-stranded RNA-mediated RNA interference of PcRXR3 caused different changes in mRNA expression of these genes in different tissues and resulted in decreased expression of PcEcR2 mRNA, which suggested a collaborative relationship between PcEcR2 and PcRXR3.