DISSERTATION RESEARCH: Phylogeny and evolutionary exploration of the C3-CAM phenotypic space in Calandrinia (Montiaceae)

天竺葵酸代谢（CAM）光合作用是植物在干旱和温度胁迫下提高水分利用和光合效率的一系列复杂性状。山铁树属（Calandrinia Montiaceae）是研究CAM光合作用进化装配的理想谱系。本研究结合系统发育、解剖学、生态学、生理学、温室实验和基因表达研究，揭示了Calandrinia CAM光合作用的增量组装。鉴于持续的全球变化和全球景观酸化的加剧（约40%的地球陆地已经被认为是干旱、半干旱或半湿润的），CAM光合作用可能在未来的碳封存、可持续生物质生产和粮食作物安全方面发挥重要作用。面对这种迫在眉睫的变化，我们比以往任何时候都更有必要了解CAM光合作用的进化基础，这可能会指导目前将这种综合征设计成粮食和生物燃料作物的努力。研究人员将对代表C3、CAM和CAM中间类型的物种进行基因表达比较研究。他们将使用比较转录组学方法来回答以下问题：1)关键CAM基因的差异基因表达如何在潜在的中间类型中变化，2)哪些基因拷贝被招募到新的CAM功能中，3)在招募执行CAM的基因拷贝中是否存在平行的核苷酸/氨基酸变化，以及4)转录组数据如何帮助我们更好地区分和定义这些C3-CAM中间体？这项研究的结果将产生第一个基于谱系的CAM进化模型。

Crassulacean Acid Metabolism (CAM) photosynthesis is a complex set of traits that improves water use and photosynthetic efficiency in plants under drought and temperature stress. Calandrinia (Montiaceae) is an ideal lineage in which to investigate the evolutionary assembly of CAM photosynthesis. This research integrates phylogenetics, anatomy, ecology, physiology, greenhouse experiments, and gene expression studies to unravel the incremental assembly of CAM photosynthesis in Calandrinia. In light of ongoing global change and the increasing acidification of the global landscape (~40% of terrestrial Earth is already considered arid, semi-arid or sub-humid), CAM photosynthesis will likely play an important role in the future of carbon sequestration, sustainable biomass production, and food-crop security. With such imminent change ahead, it is more important than ever that we understand the evolutionary underpinnings of CAM photosynthesis, which may guide current efforts to engineer this syndrome into food and biofuel crops.The researchers will conduct a comparative gene expression study across species that represent C3, CAM, and CAM-intermediate types. They will use a comparative transcriptomic approach to answer the following questions: 1) how does differential gene expression of key CAM genes vary across the potentially intermediate types, 2) which gene copies are being recruited into new CAM function, 3) are there parallel nucleotide/ amino acid changes in gene copies recruited to perform CAM, and 4) how can transcriptome data help us to better differentiate and define these C3-CAM intermediates? Results from this study will yield the first lineage-based model of CAM evolution.