The expression of Sox9 during ovarian development and heat stress in yellow catfish Pelteobagrus fulvidraco

Abstract:

Since the Sox9 plays a pivotal role during ovary development, the importance of two forms of Sox9 in the process of ovarian recrudescence in yellow catfish Pelteobagrus fulvidraco was analyzed. Tissue distribution pattern showed preferential expression of Sox9a2 in brain and ovary (brain>ovary), and trace amounts was detected in stomach, while the extensive expression of Sox9a1 was observed in several tissues. A semi-quantitative RT PCR was developed to measure the mRNA levels. The high transcript levels of both isoforms in ovary were found in the reproductive phase of ovarian cycle, with the highest level in stage Ⅲ for Sox9a1 and Ⅴ for Sox9a2.While the level of Sox9 in brain dropped significantly from stage Ⅱ. The phase-dependent rising of Sox9a2 and Estradiol-17β (E2) in fish exposed to higher temperature revealed the stimulatory role of heat stress. Gene expression of Sox9a1 in ovary was not consistent with E2 level in serum of fish exposed to higher temperature. Sox9 expression in brain was contrary to the level of E2 in stage Ⅱ. The expression level of Sox9a1 and Sox9a2 were closely related to level of serum E2 in stage Ⅲ-Ⅵ. Results demonstrated Sox9a2 in ovary played a crucial role in the reproductive cycle of female yellow catfish, and Sox9a1 in ovary was not involved in controlling the reproductive cycle. In addition, we infered that temperature can affect the negative regulation between Sox9 in brain and E2, while the mechanism needs further research.