title: Recovery of heat shock-triggered released apoplastic Ca2+ accompanied by pectin methylesterase activity is required for thermotolerance in soybean seedlings.
abstract: Synthesis of heat shock proteins (HSPs) in response to heat shock (HS) is essential for thermotolerance. The effect of a Ca(2+) chelator, EGTA, was investigated before a lethal HS treatment in soybean (Glycine max) seedlings with acquired thermotolerance induced by preheating. Such seedlings became non-thermotolerant with EGTA treatment. The addition of Ca(2+), Sr(2+) or Ba(2+) to the EGTA-treated samples rescued the seedlings from death by preventing the increased cellular leakage of electrolytes, amino acids, and sugars caused by EGTA. It was confirmed that EGTA did not affect HSP accumulation and physiological functions but interfered with the recovery of HS-released Ca(2+) concentration which was required for thermotolerance. Pectin methylesterase (PME, EC 3.1.1.11), a cell wall remodelling enzyme, was activated in response to HS, and its elevated activity caused an increased level of demethylesterified pectin which was related to the recovery of the HS-released Ca(2+) concentration. Thus, the recovery of HS-released Ca(2+) in Ca(2+)-pectate reconstitution through PME activity is required for cell wall remodelling during HS in soybean which, in turn, retains plasma membrane integrity and co-ordinates with HSPs to confer thermotolerance.
authors.affiliation: Institute of Plant Biology and Department of Life Science, National Taiwan University, Taipei, Taiwan.
authors.forename: Hui-Chen
authors.initials: HC
authors.lastname: Wu
authors.forename: Shih-Feng
authors.initials: SF
authors.lastname: Hsu
authors.forename: Dan-Li
authors.initials: DL
authors.lastname: Luo
authors.forename: Shiang-Jiuun
authors.initials: SJ
authors.lastname: Chen
authors.forename: Wen-Dar
authors.initials: WD
authors.lastname: Huang
authors.forename: Huu-Sheng
authors.initials: HS
authors.lastname: Lur
authors.forename: Tsung-Luo
authors.initials: TL
authors.lastname: Jinn
mesh_terms: D000222:Adaptation, Physiological / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D002265:Carboxylic Ester Hydrolases / Q000378:metabolism*; D004533:Egtazic Acid / Q000494:pharmacology; D004951:Esterification / Q000187:drug effects; D018869:Heat-Shock Response / Q000187:drug effects; D008954:Models, Biological; D015388:Organelles / Q000187:drug effects / Q000378:metabolism; D010368:Pectins / Q000378:metabolism; D011096:Polygalacturonase / Q000378:metabolism; D055550:Protein Stability / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D036226:Seedlings / Q000187:drug effects / Q000201:enzymology*; D012995:Solubility / Q000187:drug effects; D013025:Glycine max / Q000187:drug effects / Q000201:enzymology* / Q000254:growth & development; D013054:Spectrophotometry, Atomic; D013194:Staining and Labeling; D013696:Temperature
chemical_list: D004533:Egtazic Acid; D010368:Pectins; D002265:Carboxylic Ester Hydrolases; C022323:pectinesterase; D011096:Polygalacturonase; D002118:Calcium; C003181:polygalacturonic acid
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