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Cloning and characterization of the serotonin N ‐acetyltransferase‐2 gene ( SNAT2 ) in rice ( Oryza sativa )
Author(s) -
Byeon Yeong,
Lee Hyoung Yool,
Back Kyoungwhan
Publication year - 2016
Publication title -
journal of pineal research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.881
H-Index - 131
eISSN - 1600-079X
pISSN - 0742-3098
DOI - 10.1111/jpi.12339
Subject(s) - biology , oryza sativa , microbiology and biotechnology , biochemistry , gene
The penultimate enzyme in melatonin synthesis is serotonin N ‐acetyltransferase ( SNAT ), which exists as a single copy in mammals and plants. Our recent studies of the Arabidopsis snat ‐knockout mutant and SNAT RNA i rice ( Oryza sativa ) plants predicted the presence of at least one other SNAT isogene in plants; that is, the snat ‐knockout mutant of Arabidopsis and the SNAT RNA i rice plants still produced melatonin, even in the absence or the suppression of SNAT expression. Here, we report a molecular cloning of an SNAT isogene ( Os SNAT 2 ) from rice. The mature amino acid sequences of SNAT proteins indicated that Os SNAT 2 and Os SNAT 1 proteins had 39% identity values and 60% similarity. The K m and V max values of the purified recombinant Os SNAT 2 were 371 μ m and 4700 pmol/min/mg protein, respectively; the enzyme's optimal activity temperature was 45°C. Confocal microscopy showed that the Os SNAT 2 protein was localized to both the cytoplasm and chloroplasts. The in vitro enzyme activity of Os SNAT 2 was severely inhibited by melatonin, but the activities of sheep SNAT (Oa SNAT ) and rice Os SNAT 1 proteins were not. The enzyme activity of Os SNAT 2 was threefold higher than that of Os SNAT 1, but 232‐fold lower than that of Oa SNAT . The Os SNAT 1 and Os SNAT 2 transcripts were similarly suppressed in rice leaves during the melatonin induction after cadmium treatment. Phylogenetic analyses indicated that Os SNAT 1 and Os SNAT 2 are distantly related, suggesting that they evolved independently from Cyanobacteria prior to the endosymbiosis event.