Sequence characteristics, expression pattern, ovarian maintenance function and action mechanism of SIRT1 in Chlamys...

SIRT1 (silent mating type information regulation 2 homolog 1), a histone deacetylase in Sirtuin family, regulates ovarian development and aging in higher mammals, but its role in invertebrates remains unexplored. This study investigated SIRT1 in the scallop Chlamys farreri. Its 2382 bp CDS (coding sequence) encodes 793 amino acids with the NTERM activation motif, the catalytic activity center and the ESA domain. QRT-PCR revealed that SIRT1 expression level in gonads was significantly higher than that in other tissues. In ovary, SIRT1 expression was the highest at growing stage, in the testes, the gene was highly expressed at growing stage and mature stage, suggesting it was related to the oocyte development, spermatocyte development and the sperm maturation. Furthermore, injection experiment showed resveratrol (SIRT1 activator) up-regulated SIRT1' expression, then oocyte numbers were increased but oocytes' maturity were suppressed, while nicotinamide (SIRT1 inhibitor) down-regulated SIRT1' expression, then oocyte numbers were reduced but oocytes' maturity were accelerated, suggesting SIRT1 can promote the oocytes proliferation while delay the oocytes maturation to prevent ovarian aging. Yeast one-hybrid and electrophoretic mobility shift assay confirmed SIRT1 binds Chlamys farreri FOXL2 via two sequences (SIF1: +28-+35; SIF2: +53-+60). Dual-luciferase reporter system showed FOXL2 could up-regulate SIRT1. It was worth mentioning that FOXL2 expression was up-regulated when nicotinamide down-regulated SIRT1 expression in ovaries, indicating there was a positive and negative feedback regulation between SIRT1 and FOXL2 expression, we speculate that those two genes play a crucial role in the development and maintenance of Chlamys farreri ovarian function.