Evolution and expression analysis of carotenoid cleavage oxygenase gene family in Chinese mitten crab Eriocheir sinensis.

Carotenoid cleavage oxygenase (CCO) plays a pivotal role in various biological activities, including antioxidant and immune functions in animals. This paper investigates the evolution and expression of CCO genes based on three chordates and 27 arthropods. Aquatic animals exhibit a higher abundance of CCO genes. Despite this, research on CCO in crustaceans has been notably limited, with a complete absence of any previous studies on the CCO genes for the Chinese mitten crab (Eriocheir sinensis). In this study, six CCO genes were identified in the E. sinensis genome database. Results reveal that the evolution of the CCO gene family in Crustacea is primarily characterized by purifying selection, with a preference for employing similar codons. EsCCO1 and EsCCO3 were mainly expressed in the epidermal layer, and EsCCO4 was mainly expressed in the hindgut. Meanwhile, EsCCO5 and EsCCO6 were mainly expressed in the hepatopancreas and endometrium. A notable detail that different EsCCO genes demonstrate distinct expression patterns within various tissues of E. sinensis. The findings of this study offer fundamental insights that could serve as a basis for further exploration into the functions and regulatory mechanisms of CCO genes in crustacean species.