Zabalza Ana, van Dongen Joost T, Froehlich Anja, Oliver Sandra N, Faix Benjamin, Gupta Kapuganti Jagadis, Schmälzlin Elmar, Igal Maria, Orcaray Luis, Royuela Mercedes, Geigenberger Peter
Max-Planck-Institute of Molecular Plant Physiology, D-14476 Golm-Potsdam, Germany.
Plant Physiol. 2009 Feb;149(2):1087-98. doi: 10.1104/pp.108.129288. Epub 2008 Dec 19.
Plant internal oxygen concentrations can drop well below ambient even when the plant grows under optimal conditions. Using pea (Pisum sativum) roots, we show how amenable respiration adapts to hypoxia to save oxygen when the oxygen availability decreases. The data cannot simply be explained by oxygen being limiting as substrate but indicate the existence of a regulatory mechanism, because the oxygen concentration at which the adaptive response is initiated is independent of the actual respiratory rate. Two phases can be discerned during the adaptive reaction: an initial linear decline of respiration is followed by a nonlinear inhibition in which the respiratory rate decreased progressively faster upon decreasing oxygen availability. In contrast to the cytochrome c pathway, the inhibition of the alternative oxidase pathway shows only the linear component of the adaptive response. Feeding pyruvate to the roots led to an increase of the oxygen consumption rate, which ultimately led to anoxia. The importance of balancing the in vivo pyruvate availability in the tissue was further investigated. Using various alcohol dehydrogenase knockout lines of Arabidopsis (Arabidopsis thaliana), it was shown that even under aerobic conditions, alcohol fermentation plays an important role in the control of the level of pyruvate in the tissue. Interestingly, alcohol fermentation appeared to be primarily induced by a drop in the energy status of the tissue rather than by a low oxygen concentration, indicating that sensing the energy status is an important component of optimizing plant metabolism to changes in the oxygen availability.
即使植物在最佳条件下生长，其内部氧气浓度也可能大幅低于环境水平。我们以豌豆（Pisum sativum）根为研究对象，展示了在氧气供应减少时，适应性呼吸如何通过适应低氧环境来节省氧气。这些数据不能简单地用氧气作为底物的限制来解释，而是表明存在一种调节机制，因为引发适应性反应的氧气浓度与实际呼吸速率无关。在适应性反应过程中可识别出两个阶段：呼吸作用最初呈线性下降，随后是非线性抑制，即随着氧气供应减少，呼吸速率下降得越来越快。与细胞色素c途径不同，交替氧化酶途径的抑制仅显示出适应性反应的线性部分。向根中添加丙酮酸会导致氧气消耗速率增加，最终导致缺氧。我们进一步研究了平衡组织中体内丙酮酸可用性的重要性。利用拟南芥（Arabidopsis thaliana）的各种乙醇脱氢酶基因敲除株系，研究表明即使在有氧条件下，酒精发酵在控制组织中丙酮酸水平方面也起着重要作用。有趣的是，酒精发酵似乎主要是由组织能量状态的下降诱导的，而不是由低氧浓度诱导的，这表明感知能量状态是优化植物代谢以适应氧气供应变化的一个重要组成部分。
