Isolation and analysis of sox9 gene derived from yellow catfish Pelteobagrus fulvidraco

AbstractSox9 is one of the important genes related to sex differentiation and determination. Two partial cDNAs encoding sox9 were derived from brain, testis and ovary of yellow catfish Pelteobagrus fulvidraco using reverse transcriptase-polymerase chain reaction (RT-PCR). Sequence analysis revealed that the ovarian sox9a2 was different from sox9a1 derived from brain and testis. The identity rate of cDNA was 77%, that of amino acids was 84%, and the different nucleotides were distributed in different sites all over the cDNA. This finding confirmed that there were transcripts from two genes. Based on the homology of the amino-acid sequences for sox9 of other animals, the similarity for sox9a1 from yellow catfish and sox9 of other animals averaged 86%. The similarity for sox9a2 reached a mean of 83%. The phylogenetic analysis revealed yellow catfish sox9a1 and sox9a2 were clustered into the fish branch. And yellow catfish sox9a2 was different from the other fish sox9. There was no significant branch including all sox9 derived from testis and brain or including all ovarian sox9. The genetic distance was the same with the results of the traditional taxonomy. RT-PCR analysis indicated that sox9a1 was expressed in male and female yellow catfish forebrain as well as in gonads, whereas sox9a2 was only expressed in ovaries. The function of sox9a2 in female sex formation and ovary development needs to be studied in depth.