Chloroplastic biosynthesis of melatonin and its involvement in protection of plants from salt stress.
Chloroplastic biosynthesis of melatonin and its involvement in protection of plants from salt stress.
复制标题
DOI：
10.1038/srep41236
复制
发表时间：
2017-02-01
影响因子：
4.6
通讯作者：
Kong J
中科院分区：
文献类型：
--
作者：
Zheng X;Tan DX;Allan AC;Zuo B;Zhao Y;Reiter RJ;Wang L;Wang Z;Guo Y;Zhou J;Shan D;Li Q;Han Z;Kong J
叶绿体中的活性氧（ROS）在光合作用和胁迫条件下产生。过量的活性氧损害叶绿体和减少光合作用，如果没有适当的解毒。在目前的研究中，我们记录了叶绿体产生褪黑激素，这是一种最近发现的植物抗氧化分子。当n -乙酰血清素（褪黑素合成的底物）被喂给纯化的叶绿体时，它们以剂量反应的方式产生褪黑素。为了进一步证实叶绿体的这一功能，我们从苹果砧木Malus zumi中克隆了褪黑素合成的末端酶n-乙酰- 5 -羟色胺- o -甲基转移酶（ASMT）。体内荧光观察和Western blot证实MzASMT9定位于叶绿体中。酶动力学研究表明，重组MzASMT9蛋白合成褪黑素的Km和Vmax分别为500 μM和12 pmol/min·mg蛋白。异位表达MzASMT9的拟南芥具有更高的褪黑激素水平。重要的是，MzASMT9基因被发现在强光和盐胁迫下上调。高表达的MzASMT9增加褪黑素导致拟南芥品系比野生型植物具有更强的耐盐性，这表明ROS减少，脂质过氧化降低，光合作用增强。这些发现具有农业应用价值，可用于在各种不利环境条件下对富含褪黑激素的植物进行遗传增强，以提高作物产量。
Within the chloroplasts reactive oxygen species (ROS) are generated during photosynthesis and stressful conditions. Excessive ROS damages chloroplasts and reduces photosynthesis if not properly detoxified. In this current study, we document that chloroplasts produce melatonin, a recently-discovered plant antioxidant molecule. When N-acetylserotonin, a substrate for melatonin synthesis, was fed to purified chloroplasts, they produced melatonin in a dose-response manner. To further confirm this function of chloroplasts, the terminal enzyme for melatonin synthesis, N-acetylserotonin-O-methyltransferase (ASMT), was cloned from apple rootstock, Malus zumi. The in vivo fluorescence observations and Western blots confirmed MzASMT9 was localized in the chloroplasts. A study of enzyme kinetics revealed that the Km and Vmax of the purified recombinant MzASMT9 protein for melatonin synthesis were 500 μM and 12 pmol/min·mg protein, respectively. Arabidopsis ectopically-expressing MzASMT9 possessed improved melatonin level. Importantly, the MzASMT9 gene was found to be upregulated by high light intensity and salt stress. Increased melatonin due to the highly-expressed MzASMT9 resulted in Arabidopsis lines with enhanced salt tolerance than wild type plants, as indicated by reduced ROS, lowered lipid peroxidation and enhanced photosynthesis. These findings have agricultural applications for the genetic enhancement of melatonin-enriched plants for increasing crop production under a variety of unfavorable environmental conditions.