Molecular cloning of a plant N-acetylserotonin methyltransferase and its expression characteristics in rice
Article first published online: 6 JAN 2011
© 2011 The Authors. Journal of Pineal Research © 2011 John Wiley & Sons A/S
Journal of Pineal Research
Volume 50, Issue 3, pages 304–309, April 2011
How to Cite
Kang, K., Kong, K., Park, S., Natsagdorj, U., Kim, Y. S. and Back, K. (2011), Molecular cloning of a plant N-acetylserotonin methyltransferase and its expression characteristics in rice. Journal of Pineal Research, 50: 304–309. doi: 10.1111/j.1600-079X.2010.00841.x
- Issue published online: 11 MAR 2011
- Article first published online: 6 JAN 2011
- Received October 18, 2010; accepted November 10, 2010.
- melatonin synthesis;
- N-acetylserotonin methyltransferase;
Abstract: N-acetylserotonin methyltransferase (ASMT), the last enzyme in the synthesis of melatonin, catalyzes N-acetylserotonin into melatonin. For the first time, we cloned ASMT from rice through the analysis of recombinant Escherichia coli harboring putative rice O-methyltransferase (OMT) cDNAs. In total, 18 full-length cDNAs, which show homology to wheat caffeic acid 3-O-methyltransferase, were expressed in E. coli and induced in the presence of N-acetylserotonin; we then analyzed the production of melatonin. Only recombinant E. coli line 15 showed melatonin synthesis; no other recombinant lines produced melatonin with the addition of N-acetylserotonin in E. coli culture. Line 15 clearly exhibited in vitro ASMT enzyme activity with 0.27 pkat/mg protein. ASMT enzyme activity was inhibited by various related compounds such as N-acetyltryptamine and N-acetyltyrosine. The open reading frame of ASMT consists of 364 amino acids possessing well-conserved motifs found in plant OMT such as S-adenosyl-L-methionine–binding and catalytic sites. Induction patterns of ASMT mRNA were well matched with the production of melatonin in rice leaves during senescence, as well as several stressors.