Li Xin, Ahammed Golam Jalal, Zhang Xue-Ning, Zhang Lan, Yan Peng, Zhang Li-Ping, Fu Jian-Yu, Han Wen-Yan
Key Laboratory of Tea Quality and Safety Control, Ministry of Agriculture, Tea Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou, 310008, PR China.
College of Forestry, Henan University of Science and Technology, Luoyang, 471023, PR China.
J Hazard Mater. 2021 Feb 5;403:123922. doi: 10.1016/j.jhazmat.2020.123922. Epub 2020 Sep 11.
Arsenic is a toxic metalloid for both animals and plants. The signaling molecule melatonin can enhance abiotic stress tolerance, but the effects of As and melatonin on tea plants and the mechanisms of resilience remain unclear. Here we report that excess As causes severe oxidative stress in tea leaves as revealed by significantly reduced maximal photochemical efficiency of photosystem-II, and increased reactive oxygen species accumulation and lipid peroxidation. However, exogenous melatonin application alleviated the As phytotoxicity and increased the anthocyanin content upto 69.4 % by selectively upregulating the expression of its biosynthetic genes such as CsCHS and CsANS. Comparison of As tolerance between two tea genotypes differing in basal levels of anthocyanin revealed that a tea cultivar with increased anthocyanin content, Zijuan (ZJ), showed enhanced tolerance to As stress compared with Longjing 43 (LJ43) that contained relatively low levels of anthocyanin. Interestingly, exogenous anthocyanin also enhanced As tolerance in LJ43, but exogenous melatonin did not improve As tolerance in ZJ genotype. Analysis of As content in tea leaves revealed that melatonin significantly reduced As content in LJ43 but not in ZJ, suggesting that melatonin-enhanced tolerance to As stress is largely dependent on the basal levels of anthocyanin in tea plants.
砷对动植物来说都是一种有毒类金属。信号分子褪黑素能够增强非生物胁迫耐受性，但砷和褪黑素对茶树的影响以及茶树的恢复机制仍不清楚。在此我们报告，如通过光系统II的最大光化学效率显著降低、活性氧积累增加和脂质过氧化增加所揭示的那样，过量的砷会在茶叶中导致严重的氧化应激。然而，外源施用褪黑素减轻了砷的植物毒性，并通过选择性上调其生物合成基因如CsCHS和CsANS的表达，使花青素含量增加了69.4%。对两种花青素基础水平不同的茶树基因型之间的耐砷性进行比较发现，花青素含量增加的茶树品种紫娟（ZJ）与花青素含量相对较低的龙井43（LJ43）相比，对砷胁迫表现出更强的耐受性。有趣的是，外源花青素也增强了LJ43对砷的耐受性，但外源褪黑素并未提高ZJ基因型对砷的耐受性。对茶叶中砷含量的分析表明，褪黑素显著降低了LJ43中的砷含量，但对ZJ没有影响，这表明褪黑素增强的对砷胁迫的耐受性很大程度上取决于茶树中花青素的基础水平。
