Boron toxicity is alleviated by hydrogen sulfide in cucumber (Cucumis sativus L.) seedlings.
Boron (B) is an essential micronutrient for plants, which when occurs in excess in the growth medium, becomes toxic to plants. Rapid inhibition of root elongation is one of the most distinct symptoms of B toxicity. Hydrogen sulfide (H(2)S) is emerging as a potential messenger molecule involved in modulation of physiological processes in plants. In the present study, we investigated the role of H(2)S in B toxicity in cucumber (Cucumis sativus) seedlings. Root elongation was significantly inhibited by exposure of cucumber seedlings to solutions containing 5 mM B. The inhibitory effect of B on root elongation was substantially alleviated by treatment with H(2)S donor sodium hydrosulfide (NaHS). There was an increase in the activity of pectin methylesterase (PME) and up-regulated expression of genes encoding PME (CsPME) and expansin (CsExp) on exposure to high B concentration. The increase in PME activity and up-regulation of expression of CsPME and CsExp induced by high B concentration were markedly reduced in the presence of H(2)S donor. There was a rapid increase in soluble B concentrations in roots on exposure to high concentration B solutions. Treatment with H(2)S donor led to a transient reduction in soluble B concentration in roots such that no differences in soluble B concentrations in roots in the absence and presence of NaHS were found after 8 h exposure to the high concentration B solutions. These findings suggest that increases in activities of PME and expansin may underlie the inhibition of root elongation by toxic B, and that H(2)S plays an ameliorative role in protection of plants from B toxicity by counteracting B-induced up-regulation of cell wall-associated proteins of PME and expansins.
State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, The Chinese Academy of Sciences, Beijing 100093, People's Republic of China.
Bao-Lan
BL
Wang
Lei
L
Shi
Yin-Xing
YX
Li
Wen-Hao
WH
Zhang
D001895:Boron / Q000378:metabolism / Q000633:toxicity*; D002265:Carboxylic Ester Hydrolases / Q000235:genetics / Q000378:metabolism; D018553:Cucumis sativus / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant / Q000235:genetics; D006861:Hydrogen Peroxide / Q000378:metabolism; D006862:Hydrogen Sulfide / Q000494:pharmacology*; D008315:Malondialdehyde / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development; D036226:Seedlings / Q000187:drug effects* / Q000378:metabolism*; D012995:Solubility / Q000187:drug effects; D015854:Up-Regulation / Q000187:drug effects
D010940:Plant Proteins; C095825:expansin protein, plant; D008315:Malondialdehyde; D006861:Hydrogen Peroxide; D002265:Carboxylic Ester Hydrolases; C022323:pectinesterase; D001895:Boron; D006862:Hydrogen Sulfide