Interactive Effects of Temperature and CO2 Levels on C3 and C4 Plants

提出的研究将提高我们对在温暖环境中受高速率光呼吸影响的植物光合作用的理解。通过这项工作，我们打算通过减少光呼吸限制，从而提高C3植物的光合能力来寻找提高作物性能的新途径。我们将通过(i)研究增强光呼吸CO2细胞内再固定的机制，以及（ii） C4光合途径的早期进化来评估C3植物如何补偿高速率的光呼吸。在再固定项目中，我们将评估叶细胞周围叶绿体鞘的形成是否会增强光呼吸CO2的再同化。我们将研究在低二氧化碳和温暖的温度下是否诱导叶绿体鞘形成促进光呼吸，以及来自温暖环境的物种是否比来自凉爽气候的物种有更好的能力重新捕获光呼吸的二氧化碳。我们还将评估产生叶绿体鞘的植物是否具有与在叶绿体内释放光呼吸二氧化碳的植物相似的光呼吸二氧化碳再固定潜力。研究C4光合作用早期进化的工作将评估一套被称为“原克兰兹”解剖学特征的功能意义，这些特征出现在C3物种中，在进化谱系中与C4植物密切相关。原克兰兹解剖学可能是C4进化的第一个确定阶段，可以解释C4进化过程是如何开始的。为了研究C4性状表达的遗传控制，我们还将产生C3和C4 triplex物种之间的杂种。这将通过比较不同程度C4性状表达的杂交种的转录组来完成。除了这项研究的发现潜力之外，所提供的资金将支持培训新一代的专业知识，这些专业知识将帮助世界满足对光合作用提供的食物、纤维和可再生能源日益增长的需求。

The proposed research will improve our understanding of photosynthesis in plants affected by high rates of photorespiration occurring in warm environments. Through this work, we intend to identify new ways to improve crop performance by reducing photorespiratory limitations and thus enhancing the photosynthetic capacity of C3 plants. We will evaluate how C3 plants compensate for high rates of photorespiration by (i) studying mechanisms enhancing intracellular refixation of photorespired CO2, and (ii) the early evolution of the C4 photosynthetic pathway. In the refixation project, we will evaluate whether the formation of chloroplast sheaths around the leaf cell periphery enhances the reassimilation of photorespired CO2. We will examine if chloroplast sheath formation is inducible under low CO2 and warm temperatures promoting photorespiration, and whether species from warm environments have a better ability to recapture photorespired CO2 than those from cool climates. We will also evaluate whether plants producing chloroplast sheaths have a similar potential for photorespiratory CO2 refixation as plants engineered to release photorespired CO2 within the chloroplast. The work on the early evolution of C4 photosynthesis will evaluate the functional significance of a suite of traits termed "proto-Kranz" anatomy that appear in C3 species that are closely related to C4 plants within an evolutionary lineage. Proto-Kranz anatomy may be the first definitive stage of C4 evolution and could explain how the C4 evolutionary process is initiated. We also will generate hybrids between C3 and C4 Atriplex species in order to examine the genetic controls over the expression of C4 traits. This will be accomplished by comparing transcriptomes of hybrids with differing degrees of C4 trait expression. In addition to the discovery potential of this research, funds provided will support the training of a new generation of expertise that will help the world meet the increasing demands for food, fiber and renewable energy that photosynthesis provides.