BACKGROUND Crassulacean acid metabolism (CAM), a specialized mode of photosynthesis, enables plant adaptation to water-limited environments and improves photosynthetic efficiency via an inorganic carbon-concentrating mechanism. Kalanchoë fedtschenkoi is an obligate CAM model featuring a relatively small genome and easy stable transformation. However, the molecular responses to light quality and intensity in CAM plants remain understudied. RESULTS Here we present a genome-wide expression atlas of K. fedtschenkoi plants grown under 12 h/12 h photoperiod with different light quality (blue, red, far-red, white light) and intensity (0, 150, 440, and 1,000 μmol m-2 s-1) based on RNA sequencing performed for mature leaf samples collected at dawn (2 h before the light period) and dusk (2 h before the dark period). An eFP web browser was created for easy access of the gene expression data. Based on the expression atlas, we constructed a light-responsive co-expression network to reveal the potential regulatory relationships in K. fedtschenkoi. Measurements of leaf titratable acidity, soluble sugar, and starch turnover provided metabolic indicators of the magnitude of CAM under the different light treatments and were used to provide biological context for the expression dataset. Furthermore, CAM-related subnetworks were highlighted to showcase genes relevant to CAM pathway, circadian clock, and stomatal movement. In comparison with white light, monochrome blue/red/far-red light treatments repressed the expression of several CAM-related genes at dusk, along with a major reduction in acid accumulation. Increasing light intensity from an intermediate level (440 μmol m-2 s-1) of white light to a high light treatment (1,000 μmol m-2 s-1) increased expression of several genes involved in dark CO2 fixation and malate transport at dawn, along with an increase in organic acid accumulation. CONCLUSIONS This study provides a useful genomics resource for investigating the molecular mechanism underlying the light regulation of physiology and metabolism in CAM plants. Our results support the hypothesis that both light intensity and light quality can modulate the CAM pathway through regulation of CAM-related genes in K. fedtschenkoi.

中文翻译：

---

光响应表达图谱揭示了光质量和强度对长寿花（一种具有景天酸代谢作用的植物）的影响。


背景技术景天酸代谢（CAM）是一种特殊的光合作用模式，使植物能够适应缺水环境，并通过无机碳浓缩机制提高光合作用效率。 Kalanchoë fedtschenkoi 是一种专性 CAM 模型，具有相对较小的基因组和易于稳定转化的特点。然而，CAM 植物对光质量和强度的分子反应仍未得到充分研究。结果在这里，我们展示了在 12 小时/12 小时光周期、不同光质量（蓝光、红光、远红光、白光）和强度（0、150、440 和 1,000）下生长的 K. fedtschenkoi 植物的全基因组表达图谱。 µmol m-2 s-1）基于对黎明（光照期前 2 小时）和黄昏（黑暗期前 2 小时）收集的成熟叶片样本进行的 RNA 测序。创建了 eFP 网络浏览器，以便轻松访问基因表达数据。基于表达图谱，我们构建了光响应共表达网络，以揭示 K. fedtschenkoi 中潜在的调控关系。叶子可滴定酸度、可溶性糖和淀粉周转的测量提供了不同光处理下 CAM 大小的代谢指标，并用于为表达数据集提供生物学背景。此外，还突出显示了 CAM 相关子网络，以展示与 CAM 通路、生物钟和气孔运动相关的基因。与白光相比，单色蓝光/红光/远红光处理在黄昏时抑制了一些 CAM 相关基因的表达，同时酸积累也大大减少。 将光强度从白光的中等水平（440 μmol m-2 s-1）增加到高光处理（1,000 μmol m-2 s-1）会增加涉及黑暗二氧化碳固定和黎明时苹果酸运输的几个基因的表达，同时有机酸积累增加。结论本研究为研究 CAM 植物生理和代谢光调节的分子机制提供了有用的基因组学资源。我们的结果支持这样的假设：光强度和光质量都可以通过调节 K. fedtschenkoi 中的 CAM 相关基因来调节 CAM 途径。