The retinoid-X receptor gene from the freshwater prawn Macrobrachium nipponense: cloning, expression pattern and different responses of two splice variants during the molting cycle

Abstract

The retinoid-X receptor (RXR) is among the most conserved members of the nuclear receptor superfamily and is widely studied in vertebrate and invertebrate families. RXR plays an important role in regulation of molting and/or metamorphosis, development and reproduction. We cloned the full-length cDNA sequence of the RXR from the freshwater prawn Macrobrachium nipponense (De Haan, 1849) (MnRXR) and investigated the expression profile of MnRXR in different developmental stages of embryos, in different tissues and in the molting cycle. Two MnRXR splice variants were identified: One, MnRXR-L, the full length of which was 2472 bp, encoded a 449-amino-acid protein; the second, MnRXR-S, the full length of which was 1832 bp, encoded a 420-amino-acid protein, in which the first 29 amino-acid residues of MnRXR-L were absent. MnRXR was observed in all developmental stages of embryos and had the highest expression level in the embryonised-zoea stage, it was highly expressed in hepatopancreas, gill and intestine among the ten tissues examined. The expression of MnRXR was rapidly up-regulated in the premolt stage and rapidly down-regulated after molting. Moreover, of the two MnRXR splice variants, only MnRXR-S was induced during the molting cycle, suggesting that the two splice variants play different roles in the molting cycle.