Abstract Light cycle is an important factor affecting the total carotenoid content (TCC) in tissues of noble scallops Chlamys nobilis, but its regulatory mechanism is still unclear. In this study, adult polymorphic C. nobilis (Nan'ao Golden Scallop and common brown scallop) were exposed to three different light cycles (24L/0D, 12L/12D and 0L/24D) for 10 days. The expression of carotenoid related genes (Scavenger Receptor class B (SRB) genes, β-carotene oxygenase (BCO) genes, and Retinoic acid receptors (RAR and RXR) genes) were determined by qRT-PCR. The results revealed that 24L/0D and 0L/24D treatments significantly increased the accumulation of TCC in adductor muscle of Nan'ao Golden Scallop and common brown scallop, respectively. The deposition of carotenoids in adductor muscle was induced by the up-regulation of SRB genes, of which was then up-regulation of BCO gene expression, followed by the up-regulation of RAR and/or RXR expression, and then further induced the expression of SRB and BCO genes. In hemolymph, the absorption mechanism of carotenoids may not involve SRB genes, or other carotenoid related genes may mask the role of SRB genes. The findings of this study provide important clues for further understanding the mechanism of TCC accumulation in polymorphic C. nobilis under different light cycle.

中文翻译：

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不同光循环下多态性扇贝类胡萝卜素的调控

摘要 光循环是影响贵重扇贝Chlamys nobilis组织总类胡萝卜素含量(TCC)的重要因素，但其调控机制尚不清楚。在本研究中，成体多态性小扇贝（南澳金扇贝和普通褐扇贝）暴露于三种不同的光照周期（24L/0D、12L/12D 和 0L/24D）10 天。通过qRT-PCR测定类胡萝卜素相关基因（清道夫受体B类（SRB）基因、β-胡萝卜素加氧酶（BCO）基因和视黄酸受体（RAR和RXR）基因）的表达。结果表明，24L/0D和0L/24D处理分别显着增加了南澳金扇贝和普通褐扇贝内收肌中TCC的积累。类胡萝卜素在内收肌的沉积是由 SRB 基因的上调引起的，其中先上调 BCO 基因的表达，再上调 RAR 和/或 RXR 的表达，进而进一步诱导 SRB 和 BCO 基因的表达。在血淋巴中，类胡萝卜素的吸收机制可能不涉及SRB基因，或者其他类胡萝卜素相关基因可能掩盖了SRB基因的作用。本研究结果为进一步了解不同光循环下多态性紫鳢TCC积累机制提供了重要线索。