Molecular characterization of salt regulatory genes in Oreochromis niloticus andOreochromis mossambicus

Abstract

Polymorphisms in microsatellite DNA loci located in the salt regulatory genes have been found to
show variations in salinity tolerance and growth in fish. Five microsatellite loci located in the salt regulatory
genes prolactin 1 (Prl1), transferrin-A (TFA) and transferrin-B (TFB)have been characterized in Oreochromis
niloticus and O. mossambicus. The microsatellite markers were amplified from a total of 78 fish by
polymerase chain reaction and genotyped by polyacrylamide and agarose gel electrophoresis. The Prl1 (L-K),
PrlI-MS01, TFA and TFB loci in O. niloticus and Prl I-MS01, TFA lociinO. mossambicus were found to be
polymorphic. The average observed (Ho) and expected heterozygosity (He) values in O. niloticus were higher
than the values in O. mossambicus. Except locus Prl1(L-K) in O. niloticus, the FIS values were negative in all
other cases which indicates that both the two populations (O. niloticus and O. mossambicus) had excess of
heterozygosity. The loci Prl I-MS01 and TFA were both in O. mossambicus and O. niloticusand Prl1(L-K) in
O. niloticus were found to be significantlydeviated from Hardy-Weinberg expectations. Polymorphisms
detected in four loci in O. niloticus can be used for studying association of polymorphisms with salt tolerance
and selection of salt tolerant individuals of this species through marker assisted selection.