The role of ladderlectin in spermatogenesis and ovarian sperm storage in the black rockfish (Sebastes schlegelii)

Ladderlectin, a teleost-specific C-type lectin, has been primarily associated with innate immune defense. However, this study unveils an important role of ladderlectin in the reproductive processes of Sebastes schlegelii. Seven ladderlectin genes (SscLLs) are identified, with SscLL3604 and SscLL3605 exhibiting high testis-specificity expression. Both genes contain a C-type lectin domain (CTLD) and two carbohydrate-binding motifs (QPD and WSD), with SscLL3605 also containing a signal peptide. Notably, SscLL3604 is predominantly cytoplasmic, while SscLL3605 is found both in the cytoplasm and cell membrane. Additionally, SscLLs are primarily localized in Sertoli cells at the mRNA level but also exist in spermatids and spermatozoa at the protein level. Further analysis reveals that SscLLs are present in sperm heads and can bind to ovarian cells, hinting at a pivotal role in long-term sperm storage in ovaries. Knockdown of SscLLs in vitro demonstrates their critical role in maintaining Sertoli cells and Leydig cells within the testis. Finally, inhibition of glycosylation or treatment with antibody of SscLLs leads to an increased incidence of embryonic malformation in S. schlegelii. These findings suggest that ladderlectin may also play an important role in the regulation of reproductive processes, thereby providing an additional adaptive mechanism for the reproduction of viviparous fish.