Hdh-Tektin-4 Regulates Motility of Fresh and Cryopreserved Sperm in Pacific Abalone, Haliotis discus hannai

As structural components of sperm, tektins are thought to play a fundamental role in sperm flagellar motility. In this study, Tektin-4 (Hdh-TEKT4) gene was successfully cloned and characterized from the testis tissue in Pacific abalone, Haliotis discus hannai. The full-length cDNA of Hdh-TEKT4 was 1,983 bp, with a coding region of 1,350 bp encoding 51.83 kDa putative protein of 449 deduced amino acids. Hdh-TEKT4 contains a tektin domain including a nonapeptide signature motif (RPGVDLCRD). Fluorescence in situ hybridization revealed that Hdh-TEKT4 localized in the spermatids of Pacific abalone testis. qRT-PCR analysis showed that Hdh-TEKT4 was predominantly expressed in testis tissues. Hdh-TEKT4 mRNA expression was upregulated during the fully mature testicular developmental stage in both seasonal development and EAT exposed abalone. Furthermore, mRNA expression of Hdh-TEKT4 was significantly higher in sperm with higher motility than in sperm with lower motility during peak breeding season, induced spawning activity stages, and after cryopreservation in different cryoprotectants. Taken together, these results indicate that the expression of Hdh-TEKT4 in Pacific abalone sperm might have a positive correlation with sperm motility.