CLONING AND EXPRESSION ANALYSIS OF SPINDLIN GENE IN DIFFERENT PLOIDY RAINBOW TROUT

This study explored the different expression of spindlin gene, a meiosis spindle related factor, in diploid and triploid female rainbow trout meiosis. The spindlin cDNA was 4529 bp (GenBank login number: MN378564) including the 3′ untranslated region (UTR) of 3662 bp and 5′ untranslated region (UTR) of 141 bp. The open reading frame (ORF) was 726 bp long, encoding 241 amino acids. The relative molecular weight of the protein was 28.3 kD, the theoretical isoelectric point value was 5.94, and there was no transmembrane structure. Homology analysis showed that rainbow trout (Oncorhynchus mykiss) and silver salmon (Oncorhynchus kisutch) had the highest homology of 99.59%. Phylogenetic evolutionary trees showed rainbow trout grouped with Oncorhynchus tshawytscha and Salvelinus alpinus. RT-PCR results showed that spindlin gene was expressed in the ovary, kidney, liver, spleen, muscle, gill, heart, eye, intestine and fin tissues of diploid female rainbow trout, and the expression level in the ovary was significantly higher than that in other tissues (P<0.01). One family of female rainbow trout, spindlin gene, is particularly concerned. In the developmental stage after fertilization, 240—300 days post fertilization (dpf), the relative expression of spindlin gene in ovary tissues decreased significantly. For trout triploid female rainbow, the expression level of this gene increased significantly at the 240—330 dpf stage. In the same development stage, the expression level of spindlin gene in diploid female rainbow trout was significantly higher than that of triploid (P<0.01). Immunohistochemical results showed that the signal of Spin protein in the nucleus of primary oocyte was the strongest in diploid female rainbow trout at the stage of 240 dpf, and gradually weakened at the stage of 270—330 dpf. The signal in triploid increased gradually in oocytes during the development stage of 240—330 dpf. Abnormal meiosis is the key cause of gonadal abortion. The results of this study showed that the abnormal meiosis of triploid rainbow trout was related to the low expression of spindlin gene, which may be one of the reasons for ovarian development retardation.