National Research Center of Engineering Technology for Utilization of Botanical Functional Ingredients, Collaborative Innovation Center of Utilization of Functional Ingredients from Botanicals, Key Lab of Tea Science of Education Ministry, Hunan Agricultural University, Changsha, 410128, China; Hunan Sub Center of National Tea Improvement Center, Tea Research Institute of Hunan Academy of Agricultural Sciences, Changsha, 410125, China.
Hunan Sub Center of National Tea Improvement Center, Tea Research Institute of Hunan Academy of Agricultural Sciences, Changsha, 410125, China.
Plant Physiol Biochem. 2020 Sep;154:419-428. doi: 10.1016/j.plaphy.2020.05.038. Epub 2020 Jun 2.
The amount of fluoride accumulation in tea leaves was gradually increase as the matures of tea plants, and the excessive fluoride intake can threaten people's health. Based on years of field investigations, a low level of fluoride variety Xiangbo Lǜ (XBL) and a high level of fluoride variety Zhenong 139 (ZN139) were selected.
In this study, the root, 1st and the 5th leaf of the two-year-old tea trees were used for morphological, physiological and comparative transcriptomics analysis to understand the different features of "XBL" and "ZN139" under fluoride stress conditions. The color of the 1st and 5th leaves of XBL were yellower, the activity of peroxidase, catalase and antioxidant enzyme were lower than ZN139 under the high-fluoride stress. Transcriptomics analysis indicated that core genes involved in photosynthesis rates regulation showed no significantly exchanged expression, the co-downregulation of magnesium ions transportation, while the ROS scavenging, vegetative growth and self-compatibility between the two varieties were different. Crucial genes' expression were also identified by the real-time RT-PCR.
The tea tree is one of the few plants that has a high-fluoride content, but the different varieties respond differently to fluoride stress. High-fluoride tea tree varieties, such as ZN139, have stronger ROS scavenging abilities through the use of both their non-enzymatic and enzymatic antioxidant systems which act by increasing the expression levels of inositol-1-monophosphatases and peroxidases, among others. ZN139 can also compensate for the decrease in photosynthetic rate that is associated with the ionic imbalance caused by the reduced consumption of light energy during long-periods of high fluoride stress. Reproductive development was protected in ZN139 by the up-regulated expression of S-locus glycoprotein, Mildew resistance locus o and Phospholipase D under fluoride stress, while the vegetative development of low-fluoride varieties such as XBL was retarded. More starch and cellulose were redistributed to glucose by increasing the expression levels of glycosyl transferases and hydrolases to provide more energy for processes involved in the response and tolerance towards fluoride stress.
随着茶树的成熟，茶叶中的氟积累量逐渐增加，过量的氟摄入会威胁到人们的健康。基于多年的实地调查，选择了低氟品种香波绿（XBL）和高氟品种镇沅 139（ZN139）。
本研究以两年生茶树的根、第 1 叶和第 5 叶为材料，进行形态、生理和比较转录组学分析，了解氟胁迫下“XBL”和“ZN139”的不同特征。在高氟胁迫下，XBL 的第 1 叶和第 5 叶颜色变黄，过氧化物酶、过氧化氢酶和抗氧化酶活性低于 ZN139。转录组学分析表明，参与光合作用调控的核心基因表达没有明显变化，镁离子转运协同下调，而两种品种之间的 ROS 清除、营养生长和自交性则不同。通过实时 RT-PCR 也鉴定了关键基因的表达。
茶树是少数几种含氟量高的植物之一，但不同品种对氟胁迫的反应不同。高氟茶树品种如 ZN139，通过增加肌醇-1-单磷酸酶和过氧化物酶等的表达水平，利用非酶和酶抗氧化系统，具有更强的 ROS 清除能力，从而减轻氟胁迫对光合作用的影响。ZN139 还可以通过增加 S-位点糖蛋白、白粉病抗性位点 O 和磷脂酶 D 的表达，在氟胁迫下保护生殖发育，而低氟品种如 XBL 的营养生长则受到抑制。通过增加糖基转移酶和水解酶的表达水平，将更多的淀粉和纤维素重新分配到葡萄糖中，为应对和耐受氟胁迫的过程提供更多的能量。
