Crassulacean acid metabolism (CAM) has evolved from a C3 ground state to increase water use efficiency of photosynthesis. During CAM evolution, selective pressures altered the abundance and expression patterns of C3 genes and their regulators to enable the trait. The circadian pattern of CO2 fixation and the stomatal opening pattern observed in CAM can be explained largely with a regulatory architecture already present in C3 plants. The metabolic CAM cycle relies on enzymes and transporters that exist in C3 plants and requires tight regulatory control to avoid futile cycles between carboxylation and decarboxylation. Ecological observations and modeling point to mesophyll conductance as a major factor during CAM evolution. The present state of knowledge enables suggestions for genes for a minimal CAM cycle for proof-of-concept engineering, assuming altered regulation of starch synthesis and degradation are not critical elements of CAM photosynthesis and sufficient malic acid export from the vacuole is possible. Expected final online publication date for the Annual Review of Plant Biology, Volume 72 is May 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

中文翻译：

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Crassulacean酸代谢工程。

Crassulacean酸代谢（CAM）已从C3基态发展为增加光合作用的水分利用效率。在CAM进化过程中，选择性压力改变了C3基因及其调控因子的丰度和表达模式，从而使该特性得以实现。在CAM中观察到的CO2固定的昼夜节律模式和气孔开放模式可以用C3植物中已经存在的调控体系来解释。代谢CAM循环依赖于C3植物中存在的酶和转运蛋白，需要严格的调节控制，以避免在羧化和脱羧之间无用的循环。生态学观察和建模表明，叶肉电导是CAM进化过程中的主要因素。目前的知识状态可以为基因的建议提供最小的CAM周期，以进行概念验证工程，假设改变淀粉合成和降解的调控不是CAM光合作用的关键因素，并且有可能从液泡中充分排出苹果酸。《植物生物学年度评论》第72卷的最终最终在线发布日期为2021年5月。有关修订的估算，请参见http://www.annualreviews.org/page/journal/pubdates。