Leibniz Institute of Plant Genetics and Crop Plant Research, 06466 Gatersleben, Germany
Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, United Kingdom.
Plant Cell. 2020 Dec;32(12):3689-3705. doi: 10.1105/tpc.20.00132. Epub 2020 Oct 22.
Crassulacean acid metabolism (CAM) evolved in arid environments as a water-saving alternative to C photosynthesis. There is great interest in engineering more drought-resistant crops by introducing CAM into C plants. However, it is unknown whether full CAM or alternative water-saving modes would be more productive in the environments typically experienced by C crops. To study the effect of temperature and relative humidity on plant metabolism in the context of water saving, we coupled a time-resolved diel (based on a 24-h day-night cycle) model of leaf metabolism to an environment-dependent gas-exchange model. This combined model allowed us to study the emergence of CAM as a trade-off between leaf productivity and water saving. We show that vacuolar storage capacity in the leaf is a major determinant of the extent of CAM. Moreover, our model identified an alternative CAM cycle involving mitochondrial isocitrate dehydrogenase as a potential contributor to initial carbon fixation at night. Simulations across a range of environmental conditions show that the water-saving potential of CAM strongly depends on the daytime weather conditions and that the additional water-saving effect of carbon fixation by isocitrate dehydrogenase can reach 11% total water saving for the conditions tested.
景天酸代谢 (CAM) 是在干旱环境中作为 C 光合作用的节水替代途径进化而来的。通过将 CAM 引入 C 植物来设计更抗旱的作物引起了广泛的关注。然而，目前还不清楚在 C 作物通常经历的环境中，完全的 CAM 或替代节水模式是否会更具生产力。为了在节水的背景下研究温度和相对湿度对植物代谢的影响，我们将基于 24 小时昼夜循环的时间分辨的昼夜模型与依赖环境的气体交换模型相结合。该组合模型使我们能够研究 CAM 的出现作为叶片生产力和节水之间的权衡。我们表明，叶片中的液泡储存能力是 CAM 程度的主要决定因素。此外，我们的模型还确定了涉及线粒体异柠檬酸脱氢酶的替代 CAM 循环，作为夜间初始碳固定的潜在贡献者。在一系列环境条件下的模拟表明，CAM 的节水潜力强烈依赖于白天的天气条件，并且异柠檬酸脱氢酶固定碳的额外节水效果可达到测试条件下总节水 11%。
