In plants, melatonin production is strictly regulated, unlike the production of its precursor, serotonin, which is highly inducible in response to stimuli, such as senescence and pathogen exposure. Exogenous serotonin treatment does not greatly induce the production of N‐acetylserotonin (NAS) and melatonin in plants, which suggests the possible existence of one or more regulatory genes in the pathway for the biosynthesis of melatonin from serotonin. In this report, we found that NAS was rapidly and abundantly converted into serotonin in rice seedlings, indicating the presence of an N‐acetylserotonin deacetylase (ASDAC). To clone the putative ASDAC gene, we screened 4 genes that were known as histone deacetylase (HDAC) genes, but encoded proteins targeted into chloroplasts or mitochondria rather than nuclei. Of 4 recombinant Escherichia coli strains expressing these genes, one E. coli strain expressing the rice HDAC10 gene was found to be capable of producing serotonin in response to treatment with NAS. The recombinant purified rice HDAC10 (OsHDAC10) protein exhibited ASDAC enzyme activity toward NAS, N‐acetyltyramine (NAT), N‐acetyltryptamine, and melatonin, with the highest ASDAC activity for NAT. In addition, its Arabidopsis ortholog, AtHDAC14, showed similar ASDAC activity to that of OsHDAC10. Both OsHDAC10 and AtHDAC14 were found to be expressed in chloroplasts. Phylogenetic analysis indicated that ASDAC homologs were present in archaea, but not in cyanobacteria, which differs from the distribution of serotonin N‐acetyltransferase (SNAT). This suggests that SNAT and ASDAC may have evolved differently from ancestral eukaryotic cells.

中文翻译：

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水稻组蛋白脱乙酰基酶10和拟南芥组蛋白脱乙酰基酶14基因编码N-乙酰5-羟色胺脱乙酰酶，催化N-乙酰5-羟色胺转化为5-羟色胺，这是植物褪黑素生物合成的逆反应。

在植物中，褪黑激素的产生受到严格的调节，这与其褪色素的前体的产生不同，后者是对衰老和病原体暴露等刺激产生高度诱导作用的。外源性5-羟色胺处理不会在植物中极大地诱导N-乙酰5-羟色胺（NAS）和褪黑激素的产生，这表明从5-羟色胺生物合成褪黑激素的途径中可能存在一个或多个调控基因。在此报告中，我们发现NAS在水稻幼苗中迅速大量转化为5-羟色胺，表明存在N-乙酰5-羟色胺脱乙酰基酶（ASDAC）。为了克隆假定的ASDAC基因，我们筛选了4个被称为组蛋白脱乙酰基酶（HDAC）的基因。）基因，但编码的蛋白质靶向叶绿体或线粒体而不是细胞核。在表达这些基因的4种重组大肠杆菌菌株中，发现一种表达水稻HDAC10基因的大肠杆菌菌株能够响应于NAS处理而产生5-羟色胺。重组纯化的水稻HDAC10（OsHDAC10）蛋白对NAS，N-乙酰酪胺（NAT），N具有ASDAC酶活性-乙酰色胺和褪黑激素，对于NAT具有最高的ASDAC活性。此外，其拟南芥直系同源基因AtHDAC14显示出与OsHDAC10类似的ASDAC活性。发现OsHDAC10和AtHDAC14都在叶绿体中表达。系统发育分析表明，古细菌中存在ASDAC同源物，而蓝细菌中不存在ASDAC同源物，这与血清素N乙酰转移酶（SNAT）的分布不同。这表明SNAT和ASDAC的进化可能不同于祖先的真核细胞。