Evolution, expression profile, and regulatory characteristics of ACSL gene family in chicken (Gallus gallus)

Long chain acyl-CoA synthetases (ACSLs), which drive the conversion of long chain fatty acid into acyl-CoA, an ingredient of lipid synthesis, have been well-acknowledged to exert an indispensable role in many metabolic processes in mammals, especially lipid metabolism. However, in chicken, the evolutionary characteristics, expression profiles and regulatory mechanisms of ACSL gene family are rarely understood. Here, we analyzed the genomic synteny, gene structure, evolutionary event and functional domains of the ACSL gene family members using bioinformatics methods. The spatiotemporal expression profiles of ACSL gene family, and their regulatory mechanism were investigated via bioinformatics analysis incorporated with in vivo and in vitro estrogen-treated experiments. Our results indicated that ACSL2 gene was indeed evolutionarily lost in the genome of chicken. Chicken ACSLs shared an AMP-binding functional domain, as well as highly conversed ATP/AMP and FACS signature motifs, and were clustered into two clades, ACSL1/5/6 and ACSL3/4, based on high sequence similarity, similar gene features and conversed motifs. Chicken ACSLs showed differential tissue expression distributions, wherein the significantly decreased expression level of ACSL1 and the significantly increased expression level of ACSL5 were found, respectively, the expression levels of the other ACSL members remained unchanged in the liver of peak-laying hens versus pre-laying hens. Moreover, the transcription activity of ACSL1, ACSL3 and ACSL4 was silenced and ACSL6 was activated by estrogen, but no response to ACSL5. In conclusion, though having highly conversed functional domains, chicken ACSL gene family is organized into two separate groups, ACSL1/5/6 and ACSL3/4, and exhibits varying expression profiles and estrogen effects. These results not only pave the way for better understanding the specific functions of ACSL genes in avian lipid metabolism, but also provide a valuable evidence for gene family characteristics.