Linking hydrogen-mediated boron toxicity tolerance with improvement of root elongation, water status and reactive oxygen species balance: a case study for rice.
Boron is essential for plant growth but hazardous when present in excess. As the antioxidant properties of hydrogen gas (H2) were recently described in plants, oxidative stress induced by excess boron was investigated along with other biological responses during rice (Oryza sativa) seed germination to study the beneficial role of H2METHODS: Rice seeds were pretreated with exogenous H2Using physiological, pharmacological and molecular approaches, the production of endogenous H2, growth status, reactive oxygen species (ROS) balance and relative gene expression in rice were measured under boron stress to investigate mechanisms of H2-mediated boron toxicity tolerance.



In our test, boron-inhibited seed germination and seedling growth, and endogenous H2production, were obviously blocked by exogenously applying H2The re-establishment of ROS balance was confirmed by reduced lipid peroxidation and ROS accumulation. Meanwhile, activities of catalase (CAT) and peroxidase (POX) were increased. Suppression of pectin methylesterase (PME) activity and downregulation of PME transcripts by H2were consistent with the alleviation of root growth inhibition caused by boron. Water status was improved as well. This result was confirmed by the upregulation of genes encoding specific aquaporins (AQPs), the maintenance of low osmotic potential and high content of soluble sugar. Increased transcription of representative AQP genes (PIP2;7 in particular) and BOR2 along with decreased BOR1 mRNA may contribute to lowering boron accumulation.



Hydrogen provides boron toxicity tolerance mainly by improving root elongation, water status and ROS balance.
College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, China.
Yu
Y
Wang
College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, China.
Xingliang
X
Duan
Institute of Botany Jiangsu Province and Chinese Academy of Sciences, Nanjing 210014, China.
Sheng
S
Xu
Institute of Botany Jiangsu Province and Chinese Academy of Sciences, Nanjing 210014, China.
Ren
R
Wang
Shuigu Environmental Protection Technological Company Ltd, Shanghai 200437, China.
Zhaozeng
Z
Ouyang
College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, China wbshenh@njau.edu.cn.
Wenbiao
W
Shen
D001895:Boron / Q000633:toxicity*; D018506:Gene Expression Regulation, Plant; D018525:Germination / Q000187:drug effects / Q000502:physiology; D006859:Hydrogen / Q000378:metabolism; D012275:Oryza / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism / Q000502:physiology; D018384:Oxidative Stress; D018517:Plant Roots / Q000254:growth & development*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D012639:Seeds / Q000187:drug effects / Q000254:growth & development; D014867:Water / Q000378:metabolism
D017382:Reactive Oxygen Species; D014867:Water; D006859:Hydrogen; D001895:Boron
Oryza sativa; ROS balance; aquaporins; boron toxicity; hydrogen gas; root elongation; seed germination; water status