A StAR-like gene involved in carotenoid metabolism and inner shell color in the freshwater pearl mussel, Hyriopsis cumingii

Carotenoids play key roles in organism coloration and have been found to have an effect on shell color. Steroidogenic acute regulatory protein-like (StAR-like) is a key gene involved in the accumulation of carotenoids. In this study, the full-length cDNA sequence of HcStAR-like, containing 994 nucleotides with an open reading frame encoding 307 amino acid residues, was isolated from the freshwater pearl mussel, Hyriopsis cumingii. HcStAR-like expression levels were significantly higher in all tissues examined in golden (G-) mussels compared with white (W-) and purple (P-) mussels (p < .05). Moreover, although HcStAR-like expression levels were higher in P-mussels than W-mussels, this difference was only significant in the hepatopancreas (p < .05). Our in situ hybridization assay indicated that StAR-like was localized to the outer fold of the mantle and the joint of the outer and middle folds of the mantle. The dsRNA interference of HcStAR-like expression in G-mussels was effective with an interference rate of 79.89% (p < .05). The total carotenoid content (TCC) in the mantle of the RNAi group decreased by 48.63% (p < .05). Our findings suggested that HcStAR-like was involved in the accumulation of carotenoids and inner shell pigmentation in H. cumingii.

Automated summary

The gene HcStAR-like is crucial for both the accumulation of carotenoids and inner shell pigmentation in the freshwater pearl mussel, Hyriopsis cumingii. Expression levels of HcStAR-like also correlate with shell color in different tissues of the mussel.