A new alternative splice variant of ecdysteroid receptor ( EcR ) transcript differentially expressed during embryogenesis in the oriental river prawn Macrobrachium nipponense

Abstract

Ecdysteroids are well known as a class of steroid hormones, which not only mediate moulting in insects and crustaceans but also are involved in the reproduction and embryogenesis as well. To characterize the role of ecdysteroid receptor (EcR) in embryogenesis, a novel alternative splicing of EcR (MnEcR) was identified from the oriental river prawn Macrobrachium nipponense, and its spatio-temporal expression profile was examined during embryogenesis. The MnEcR cDNA is 2246 bp in length and encodes a protein with 487 amino acids. Quantitative real-time PCR analysis revealed that the relative amount of MnEcR transcripts was low at cleavage stage, gradually increased from blastula stage, and reached at a peak at the metanauplius when the Y-organ appeared and, thereafter, dramatically decreased at the protozoea and back to a low level at the zoea. Such a dynamic expression profile of MnEcR mRNA is paralleled by fluctuation of ecdysteroids during morphogenesis in the prawn M. rosenbergii and Palaemon serratus. Hybridization in situ demonstrated MnEcR transcripts were localized to the epidermis of appendage rudiments in metanauplius and the cuticle membrane of the thoracic legs and telson in zoeas, suggesting a role for MnEcR in the development of appendages. These results indicated that MnEcR associated with ecdysteroids might be essential for morphogenesis during embryogenesis in the prawn.