A Comparative Genomic and Transcriptomic Survey Provides Novel Insights into N-Acetylserotonin Methyltransferase (ASMT) in Fish.

Melatonin is a multifunctional bioactive molecule that plays comprehensive physiological roles in all living organisms. N -acetylserotonin methyltransferase (ASMT, also known as hydroxyindole O -methyltransferase or HIOMT) is the final enzyme for biosynthesis of melatonin. Here, we performed a comparative genomic and transcriptomic survey to explore the ASMT family in fish. Two ASMT isotypes ( ASMT1 and ASMT2 ) and a new ASMT-like ( ASMTL ) are all extracted from teleost genomes on the basis of phylogenetic and synteny analyses. We confirmed that C-terminal of the ASMTL proteins (ASMTL-ASMT) is homology to the full length of ASMT1 and ASMT2. Our results also demonstrate that the two ASMT isotypes and their distribution in teleosts seem to be the result of combinations of whole-genome duplication (WGD) and gene loss. Differences were also observed in tissue distribution and relative transcript abundances of ASMT1 , ASMT2 and ASMTL through transcriptomic analysis. Protein sequence alignment and 3D structure prediction of ASMTs and ASMTL suggest differential roles for these ASMT genes. In summary, our current work provides novel insights into the ASMT genes in fish by combination of genomic and transcriptomic data.