Sex-lethal gene of the Chinese mitten crab Eriocheir sinensis: cDNA cloning, induction by eyestalk ablation, and expression of two splice variants in males and females.

Sex-lethal (Sxl) plays an important role in sex determination in insects. In this study, the full-length complementary DNA (cDNA) of Sxl of the Chinese mitten crab Eriocheir sinensis (EsSxl) was cloned. EsSxl is expressed during different developmental stages of embryos, and its expression level in the cleavage stage is lower than that in other stages of embryonic development, such as the original zoea stage when it reaches the highest level. The expression level of EsSxl in eight different tissues was investigated. EsSxl was expressed in seven examined tissues, excluding eyestalk, and the highest expression levels were observed in testis and hepatopancreas. EsSxl expression in testis was 13-fold higher than that in ovary. After induction by eyestalk ablation, changes in EsSxl expression were also tissue-specific, with EsSxl expression increasing by 2.6-fold and 11.5-fold in ovary and muscle, respectively, between 0 and 7 days after eyestalk ablation and decreasing by 2.0-fold in testis between 0 and 3 days after eyestalk ablation and by 265-fold in hepatopancreas between 0 and 7 days after eyestalk ablation. Two splice variants of EsSxl were identified, and the only difference between them was a 77-bp alternatively spliced intron that is transcripted in EsSxl1 and skipped in EsSxl2. Both variants were expressed in males and females, demonstrating the lack of a sex-specific expression pattern for Sxl in Chinese mitten crab.