Correia Barbara, Hancock Robert D, Amaral Joana, Gomez-Cadenas Aurelio, Valledor Luis, Pinto Glória
Department of Biology, Centre for Environmental and Marine Studies, University of Aveiro, Aveiro, Portugal.
Cell and Molecular Sciences, The James Hutton Institute, Dundee, United Kingdom.
Front Plant Sci. 2018 Jun 20;9:819. doi: 10.3389/fpls.2018.00819. eCollection 2018.
Aiming to mimic a more realistic field condition and to determine convergent and divergent responses of individual stresses in relation to their combination, we explored physiological, biochemical, and metabolomic alterations after drought and heat stress imposition (alone and combined) and recovery, using a drought-tolerant clone. When plants were exposed to drought alone, the main responses included reduced pre-dawn water potential (Ψ) and gas exchange. This was accompanied by increases in malondialdehyde (MDA) and total glutathione, indicative of oxidative stress. Abscisic acid (ABA) levels increased while the content of jasmonic acid (JA) fell. Metabolic alterations included reductions in the levels of sugar phosphates accompanied by increases in starch and non-structural carbohydrates. Levels of α-glycerophosphate and shikimate were also reduced while free amino acids increased. On the other hand, heat alone triggered an increase in relative water content (RWC) and Ψ. Photosynthetic rate and pigments were reduced accompanied by a reduction in water use efficiency. Heat-induced a reduction of salicylic acid (SA) and JA content. Sugar alcohols and several amino acids were enhanced by the heat treatment while starch, fructose-6-phosphate, glucose-6-phosphate, and α-glycerophosphate were reduced. Contrary to what was observed under drought, heat stress activated the shikimic acid pathway. Drought-stressed plants subject to a heat shock exhibited a sharp decrease in gas exchange, Ψ and JA, no alterations in electrolyte leakage, MDA, starch, and pigments and increased glutathione pool in relation to control. Comparing this with drought stress alone, subjecting drought stressed plants to an additional heat stress alleviated Ψ and MDA, maintained an increased glutathione pool and reduced starch content and non-structural carbohydrates. A novel response triggered by the combined stress was the accumulation of cinnamate. Regarding recovery, most of the parameters affected by each stress condition reversed after re-establishment of control growing conditions. These results highlight that the combination of drought and heat provides significant protection from more detrimental effects of drought-stressed eucalypts, confirming that combined stress alter plant metabolism in a novel manner that cannot be extrapolated by the sum of the different stresses applied individually.
为了模拟更现实的田间条件，并确定个体胁迫及其组合的趋同和发散反应，我们使用一个耐旱克隆体，研究了干旱和热胁迫（单独和组合）及恢复后生理、生化和代谢组学的变化。当植物仅遭受干旱时，主要反应包括黎明前水势（Ψ）和气体交换降低。这伴随着丙二醛（MDA）和总谷胱甘肽增加，表明存在氧化应激。脱落酸（ABA）水平升高，而茉莉酸（JA）含量下降。代谢变化包括糖磷酸水平降低，同时淀粉和非结构性碳水化合物增加。α-甘油磷酸和莽草酸水平也降低，而游离氨基酸增加。另一方面，仅热胁迫会导致相对含水量（RWC）和Ψ增加。光合速率和色素降低，同时水分利用效率降低。热胁迫导致水杨酸（SA）和JA含量降低。热处理增强了糖醇和几种氨基酸的含量，而淀粉、6-磷酸果糖、6-磷酸葡萄糖和α-甘油磷酸减少。与干旱条件下观察到的情况相反，热胁迫激活了莽草酸途径。遭受热激的干旱胁迫植物气体交换、Ψ和JA急剧下降，电解质渗漏、MDA、淀粉和色素无变化，与对照相比谷胱甘肽池增加。与单独的干旱胁迫相比，对干旱胁迫植物施加额外的热胁迫可缓解Ψ和MDA，维持增加的谷胱甘肽池，并降低淀粉含量和非结构性碳水化合物。组合胁迫引发的一个新反应是肉桂酸盐的积累。关于恢复，在重新建立对照生长条件后，受每种胁迫条件影响的大多数参数都发生了逆转。这些结果表明，干旱和热的组合可显著保护桉树免受干旱胁迫的更有害影响，证实组合胁迫以一种新的方式改变植物代谢，这种方式不能通过单独施加的不同胁迫的总和来推断。
