MOLECULAR CHARACTERIZATION AND TISSUE DISTRIBUTION OF SODIUM-DEPENDENT PHOSPHATE COTRANSPORTER GENE (SLC34A2) IN GRASS CARP CTENOPHARYNGODON IDELLA

To reveal the mechanism of grass carp (Ctenopharyngodon idella) on absorbing phosphate, a sodium-dependent phosphate cotransporter gene (Slc34a2) was cloned from grass carp intestine. The full-length cDNA of Slc34a2 was consisted of 2446 bp with a 1938 bp open reading frame, a 47 bp 5'UTR (untranslated region) and a 461 bp 3' UTR, which encoded 645 amino acids with an estimated formula of C3215H5125N801O902S30 that has 70.39 kD molecular weight, a 5.68 isoelectric point, and 0.458 grand average of hydropathicity. The putative grass carp SLC34A2 protein had eleven membrane-spanning domains with the extracellular N-termini and intracellular C-termini and acysteinerich region in C-termini domain as well as four N-glycosylation sites in second extracellular loop. The phylogenetic tree based onneighbor-joining method revealed that the SLC34A2 of grass carp was clustered with other teleost fish. The deduced amino acid sequence showed 90.3% and 87.0% sequence identity to Cyprinus carpio and Danio rerio, respectively. The highest level of Slc34a2 mRNA was in the intestine, followed by the liver, gill, kidney, spleen, skin, muscle, brain and head-kidney. Through cloning the full-length of Slc34a2 grass carp, this paper studied the characteristics of SLC34A2 structure, function and tissues distribution for laying the molecular foundation for further efforts to improve phosphate utilization and minimize the excretion of phosphorus.