Abstract：The full-length cDNA of acetyl-CoA carboxylase β (ACC2) gene was cloned from grass carp (Ctenopharyngodon idella) by reverse transcription PCR (RT-PCR) and rapid amplification of cDNA ends (RACE) methods. The expression of ACC2 gene in the hepatopancreas, spleen, brain, anterior intestine, mid-intestine, posterior intestine, kidney, muscle, heart and adipose tissues of grass carp was analyzed by quantitative real-time PCR method. Meanwhile, the ACC2 gene expression in the hepatopancreas and muscle of grass carp fed with diets containing different lipid sources for 12 weeks was studied. In addition, ACC2 gene expression in the hepatopancreas of grass carp at 3, 6, 12 and 24 h starvation and refeeding was also investigated. The results showed that the full-length cDNA of ACC2 gene was 7 533 bp with a 7 149 bp open reading frame encoding 2 382 amino acids. The calculated molecular weight of ACC2 protein was 268.34 ku and the isoelectric point was 6.13. In addition, alternative splicing was observed in ACC2 gene of grass carp and one isoform was formed, where eight amino acids were absent compared with that of the 268.34 ku ACC2 protein. The expression of ACC2 gene was detected in all examined tissues. The highest expression level of ACC2 mRNA was found in the muscle (29.13), which was significantly higher than that in other tissues except for brain, anterior intestine and heart (P<0.05), whereas its expression in the hepatopancreas (only 1.90) was the lowest. There were no significant differences in ACC2 mRNA expression level in the hepatopancreas and muscle of grass carp after fed with diets containing different lipid sources (P>0.05). The highest expression level of ACC2 mRNA (6.17) in the hepatopancreas of grass carp was detected in the group of 12 h starvation and refeeding (P<0.05), which then decreased obviously and declined to 2.84 in the group of 24 h starvation and refeeding. In summary, we have cloned the full-length cDNA of ACC2 gene from grass carp. Compared with other vertebrates, the main functional sites (ATP-binding site and biotin-binding site) are basically conserved. The active lipolysis tissues, such as muscle, are the main ACC2 gene expressing tissues in grass carp. Moreover, the hepatopancreas ACC2 mRNA expression level is not affected after the grass carp fed with diets containing different lipid sources, and the highest expression level of ACC2 mRNA in the hepatopancreas of grass carp is detected when 12 h starvation and refeeding.
