Evolution and function of an unusual photosynthetic metabolism: Portulaca, the C4-CAM plant

一种不寻常的光合代谢的进化和功能：马齿苋（C4-CAM 植物）

基本信息

批准号：
1754662
负责人：
Erika Edwards
金额：
$ 72.28万
依托单位：
Yale University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2018
资助国家：
美国
起止时间：
2018-07-01 至 2023-06-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1754662&HistoricalAwards=false
关键词：
Evolution function unusual photosynthetic metabolism

项目摘要

Plants perform photosynthesis to transform carbon dioxide and sunlight into stored chemical energy - carbohydrates - that the rest of life relies upon. Photosynthesis works well when plants are not exposed to environmental stress, but when plants are too hot, or drought stressed, this process becomes inefficient. Plants have evolved two main alternative photosynthetic pathways in response to environmental stresses, CAM and C4 photosynthesis. C4 and CAM have each evolved many times, and it has been thought that C4 evolved in response to hot temperatures and CAM in response to drought. Similarly, these two pathways were assumed to be incompatible at cellular and genetic levels. However, a C4-CAM plant has been discovered: Portulaca, which performs C4 photosynthesis normally, but performs CAM under drought. This project aims to understand the function and ecological significance of a C4-CAM photosynthetic system. The research team will discover how many times C4-CAM evolved in Portulaca, and will identify the spatial configuration of both pathways within the leaf. They will identify the genes that regulate both pathways, and will compare the ecological ranges of C4-CAM species with relatives that do not have this trait. Finally, they will survey other plants to identify additional origins of this novel photosynthesis type. This research may contribute to crop improvement- for example, efforts to engineer C4 into rice, and CAM into poplar. A C4-CAM crop could be highly productive when water is prevalent, but drought-resistant when water is scarce. In addition, this award will support a broad range of educational activities, including post-doctoral and graduate student training, undergraduate research, and high school teacher training and curriculum development.C4 and CAM photosynthesis are two metabolic pathways that have evolved multiple times. Though biochemically similar, each pathway requires a unique suite of anatomical characters in order to work efficiently, and conventional wisdom holds that these characters are antagonistic, such that anatomy that facilitates efficient C4 will simultaneously disadvantage a CAM metabolism. This widely accepted view cannot, however, accommodate Portulaca, the only plants currently known to operate both C4 and CAM cycles within a single leaf. Recent work suggests that ancestral Portulaca was a facultative CAM plant, and evolved a C4 system while maintaining CAM capability at least three times. The proposed research will test this hypothesis and develop Portulaca as a model lineage for investigating the evolutionary connectivity of C4 and CAM pathways. This project aims to: 1) confirm the existence of facultative CAM in all major Portulaca lineages, and characterize CAM and C4 biochemical cycles and differential gene expression in 7 species representing all C4 origins; 2) identify the spatial configuration of C4 and CAM cycles within the leaf, using in situ hybridization and protein immunolocalization; 3) utilize recently designed targeted gene enrichment baits (HybSeq) to sequence key photosynthetic (and other) genes from across Portulaca to improve phylogenetic resolution and analyze convergent molecular adaptation across the group; 4) characterize and contrast the climatic envelopes occupied by C4-CAM Portulaca and C3-CAM related lineages; and 5) initiate phylogenetically-informed physiological surveys to discover additional C4-CAM plants in other clades.This award was co-funded in the Biology Directorate of NSF by Integrative Ecological Physiology in the Integrative Organismal Systems Division, Systematics and Biodiversity Science in the Division of Environmental Biology, and Emerging Frontiers.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

植物进行光合作用，将二氧化碳和阳光转化为储存的化学能 - 碳水化合物 - 生命的其余部分。当植物不承受环境压力时，光合作用效果很好，但是当植物太热或干旱压力时，该过程就会效率低下。植物响应环境应力，CAM和C4光合作用而进化了两种主要的光合途径。 C4和CAM都已经演变了多次，人们认为C4响应于炎热的温度和CAM响应干旱而发展。同样，认为这两种途径在细胞和遗传水平上是不兼容的。但是，已经发现了C4-CAM植物：Portulaca，它通常会进行C4光合作用，但在干旱下进行凸轮。该项目旨在了解C4-CAM光合系统的功能和生态意义。研究团队将发现C4-CAM在Portulaca中演变的次，并将确定叶子内这两种途径的空间配置。他们将确定调节这两种途径的基因，并将C4-CAM物种的生态范围与没有这种特征的亲戚进行比较。最后，他们将调查其他植物，以识别这种新型光合作用类型的其他起源。这项研究可能有助于作物的改善 - 例如，将C4努力的努力以及CAM纳入Poplar。当水普遍存在时，C4-CAM作物可能会高效，但是当水稀缺时耐旱。此外，该奖项将支持广泛的教育活动，包括博士后和研究生培训，本科研究以及高中教师培训和课程发展。C4和CAM Photosynsiss是两种代谢途径，这些途径已经发展了多次。尽管在生化上相似，但每种途径都需要一个独特的解剖特征才能有效地工作，并且传统的智慧认为这些特征是拮抗的，因此促进有效C4的解剖结构会同时发生CAM代谢。但是，这种被广泛接受的视图不能容纳Portulaca，这是目前已知的唯一在单叶中运行C4和CAM循环的植物。最近的工作表明，祖先的Portulaca是一种辅助凸轮植物，并且在保持CAM能力至少三次的同时发展了C4系统。拟议的研究将检验该假设，并开发portulaca作为研究C4和CAM途径的进化连通性的模型谱系。该项目的目的是：1）确认在所有主要的portulaca谱系中都存在辅助CAM，并在代表所有C4起源的7种中表征CAM和C4生化周期和差异基因表达； 2）使用原位杂交和蛋白质免疫定位确定叶片内C4和CAM循环的空间构型； 3）利用最近设计的靶向基因富集诱饵（HYBSEQ）来序列关键的光合作用基因（和其他）基因，以改善系统发育分辨率，并分析整个组的收敛分子适应； 4）表征和对比C4-CAM Portulaca和C3-CAM相关谱系所占据的气候信封；和5）启动系统发育的生理调查，以发现其他进化枝中的其他C4-CAM植物。该奖项是由综合生态生理生理学在NSF的生物学局中共同资助的，该奖项是综合生物体系统部门，系统制度和系统制度部门，系统制度和生物多样性科学在环境生物学领域和emerging的领域。使用基金会的智力优点和更广泛的影响评估标准进行评估。