Meeting Abstract
P3.135 Jan. 6 Comparative studies of the EcR and RXR genes in allopatric Uca species ANILKUMAR, G*; HOPKINS, PM; DURICA, DS; Sree Narayana College; University of Oklahoma; University of Oklahoma ddurica@ou.edu
In crustaceans, the retinoid X receptor (RXR) is the heterodimer partner of the ecdysteroid receptor (EcR), a transcriptional regulator of growth and/or reproduction. Recent analyses of RXR-encoding genes of the fiddler crab Uca pugilator and the land crab Gecarcinus lateralis have revealed that, unlike their vertebrate homologs, these RXRs contain variant ligand binding domain (LBD) sequences resulting from alternative splicing. We present sequence information on the EcR and RXR genes of the crab, Uca annulipes, an inhabitant of the intertidal zone of the estuaries of Muzhupilangad (Kannur, India). Using RT-PCR, we have recovered cDNAs from ovarian tissues and examined them for splicing variants in the LBD. Within the LBD region sequenced, the two Uca RXR homologs share 97% nucleotide sequence identity, and encode identical proteins with the exception of two adjacent amino acid substitutions at the beginning of the helix 9 region. Isoform variants identical in composition to those observed in Uca pugilator were identified: a hinge region variant differing by the addition or omission of a 5-6 amino acid sequence, and a variant in the H1-3 loop region, differing by the addition or omission of a 33 amino acid sequence. A H7-8 isoform, as identified in G. lateralis, was not observed. Nucleotide identities in the U. annulipes EcR and RXR DNA binding domains(DBD) are also high (~96%), encoding identical proteins over the region thus far sequenced. Intron structure within the DBDs is also highly conserved, although the UpEcR gene contains an intron/exon organization distinct from that observed in insects. Primers designed for the EcR and RXR genes have been validated for the U. annulipes homologs, and Q-RTPCR experiments are in progress quantifying receptor transcript levels during oocyte maturation.
