Dimensions: Collaborative Proposal: Molecular, ecological and evolutionary dynamics of carbon fixation and diversification in Agavoideae (Asparagaceae) and Oncidiinae (Orchidaceae)

光合作用是支持地球上绝大多数生命的基本过程。然而，对于生活在缺水条件下的植物来说，炎热和干燥的气候条件会降低光合作用的效率。为了抵消这些条件，一些植物利用光合作用的形式来提高它们利用水的效率。在沙漠或其他缺水栖息地生长的植物中发现的一种这样的创新被称为CAM（天冬酸代谢）。CAM创新存在于大量不同的植物谱系中，通常与茎（如仙人掌）或叶（如龙舌兰）多肉有关。拟议的研究项目将使用几种方法来解决有关植物如何使用CAM以及参与执行CAM的基因如何被调节以响应不同的环境条件的基本问题。为了实现这一目标，该项目将重点关注兰花和龙舌兰植物家族中CAM的独立进化，这两种植物都以其在缺水环境中茁壮成长的能力而闻名。该研究将为了解CAM途径的遗传基础提供基础，并有可能将其转移到经济上重要的植物上，以提高干旱条件下的水分利用效率，从而提高生产力。此外，该项目将培训本科生和研究生，包括来自代表性不足群体的个人。还计划将项目成果纳入课堂学习和更广泛的外联活动。本项目利用两个CAM光合作用实例的综合研究计划，阐明了促进生物多样性起源和维持的进化过程中生态、遗传和分子维度的联系机制。光合作用是支持地球上绝大多数生态群落生物多样性的基本过程，同时也是生活在水资源有限条件下的初级生产者的生理挑战。光合作用生物的进化史包括在极端环境条件下提高水利用效率和生产力的碳浓缩机制的反复起源。天竺葵酸代谢就是这样一种创新，它促进了维管植物谱系在一系列栖息地的多样化。该项目将整合生态学、生理学、系统发育学、遗传学和基因组学方法，以解决植物如何使用CAM以及参与CAM的基因如何在不同环境条件下受到调节的基本问题。本项目的研究系统是种类丰富的Agavoideae（天门冬科）和Oncidiinae（兰科）谱系，这两个谱系都包括CAM， C3（光合作用的典型形式）和兼性或弱CAM物种。这些系统将有助于推断两个谱系中CAM光合作用的多种增益和损失的系统发育和环境背景。RNA的比较分析将阐明C3和CAM光合作用转变的相互作用的分子和环境驱动因素，以及这些转变对物种多样性起源和维持的影响。此外，通过对CAM与C3亲本自然杂交而成的丝兰杂交种的遗传分析，以及对新兴兰花模式物种Erycina pusilla （Oncidiinae）基因表达的实验操作，将测试与CAM增益和损失相关的基因功能的变化。

Photosynthesis is a basic process supporting the vast majority of life on Earth. However, for plants living under water-limited conditions, photosynthetic productivity can be reduced by hotter and drier climatic conditions. To counteract these conditions, some plants utilize forms of photosynthesis that increase the efficiency with which they use water. One such innovation seen in plants that grow in deserts or other water-limited habitats is referred to as CAM (Crassulacean Acid Metabolism). The CAM innovation is found in a large number of diverse plant lineages and typically associated with stem (e.g. cacti) or leaf (e.g. agaves) succulence. The proposed research project will use several approaches to address fundamental questions about how plants use CAM and how genes involved in performing CAM are regulated in response to varying environmental conditions. To achieve this, the project will focus on the independent evolution of CAM in the orchid and agave plant families, both of which have species known for their ability to thrive in water-limited environments. This research will provide a foundation for understanding the genetic basis of CAM pathways and potentially transfer to economically important plants for improved water use efficiency under drought conditions leading to improved productivity. Additionally, this project would result in the training of undergraduate and graduate students, including individuals from under-represented groups. There are also plans to integrate the results of the project into classroom learning and broader outreach activities.This project utilizes an integrated research program on two instances of CAM photosynthesis to illuminate the mechanisms that link ecological, genetic and molecular dimensions of the evolutionary processes that contribute to the origin and maintenance of biodiversity. Photosynthesis is a fundamental process supporting biodiversity in the vast majority of ecological communities on our planet, while at the same time a physiological challenge for primary producers living under water-limited conditions. The evolutionary history of photosynthetic organisms has included repeated origins of carbon concentrating mechanisms that increase water-use efficiency and productivity in extreme environmental conditions. Crassulacean acid metabolism is one such innovation that has facilitated diversification of vascular plant lineages in an array of habitats. The proposed project will integrate ecological, physiological, phylogenetic, genetic and genomic approaches to address fundamental questions about how plants use CAM and how genes involved in performing CAM are regulated in response to different environmental conditions. The study systems for this project are the species-rich Agavoideae (Asparagaceae) and Oncidiinae (Orchidaceae) lineages, both of which include CAM, C3 (typical form of photosynthesis) and facultative or weak CAM species. These systems will aid in inferring the phylogenetic and environmental context for multiple gains and losses of CAM photosynthesis in both lineages. Comparative analyses of RNA will illuminate the interacting molecular and environmental drivers of shifts between C3 and CAM photosynthesis and the impact of these shifts on the origin and maintenance of species diversity. Furthermore, shifts in gene function associated with the gain and loss of CAM will be tested through genetic analyses of a yucca hybrid, resulting from a natural cross between a CAM and C3 parental species, and experimental manipulations of gene expression in the emerging orchid model species, Erycina pusilla (Oncidiinae).