Adaptomics: The Evolution of C4 Photosynthesis in the Brassicales

在单子叶和双子叶种子植物家族中，C4光合作用独立于C3祖先进化了至少60次。因此，它代表了复杂适应性特征趋同进化的一个显著例子。C4光合作用可以被认为是对高温和低水可用性的适应，或者更一般地说，是对非生物胁迫条件的适应。简单地说，C4植物如何从C3祖先进化的新兴模型假定已经存在于C3植物中的基因在C4进化过程中经历其表达强度和其表达结构域的变化，这通常伴随（或先于）基因和/或基因组复制。除了这个一般模型之外，这种复杂的适应性特征背后的遗传和分子机制还没有得到很好的理解。几个C4光合物种的家庭Cleomaceae，一个姐妹家庭的拟南芥科在拟南芥目，和C3-C4光合中间物种的Moricandia属在拟南芥目，现在的发现使得有可能利用资源和工具，可用于模式植物物种拟南芥解剖的C4性状的遗传和分子机制。具体而言，该提案旨在通过C3、C3-C4中间体以及C4菊科和Cleomaceae的全基因组比较分析来鉴定和功能分析控制C4性状的基因。通过在转基因拟南芥和桑属植物中候选基因的阻遏和错误表达来验证从比较分析中得出的假设。

C4 photosynthesis has evolved at least 60-times independently from C3 ancestors in both mono- and dicotyledonous seed plant families. It thus represents a remarkable example of convergent evolution of a complex adaptive trait. C4 photosynthesis can be considered as an adaptation to high temperatures and low water availability, or, more generally, to conditions of abiotic stress. Simply spoken, the emerging model of how C4 plants evolve from C3 ancestors posits that genes that are already present in C3 plants undergo changes in their expression strength and their expression domains in the course of C4 evolution, which is frequently accompanied (or predated) by gene and/or genome duplications. Beyond this general model, the genetic and molecular mechanisms underlying this complex adaptive trait are not well understood. The discovery of several C4 photosynthetic species in the family Cleomaceae, a sister family to the Brassicaceae within the Brassicales, and of C3-C4 photosynthetic intermediate species in the genus Moricandia within the Brassicales now makes it possible to capitalize on the resources and tools available for the model plant species Arabidopsis thaliana for dissecting the genetic and molecular mechanisms underlying the C4 trait in the Brassicales. Specifically, this proposal aims at the identification and functional analysis of genes governing the C4 trait through genome-wide comparative analyses of C3, C3-C4 intermediates, and C4 Brassicaceae and Cleomaceae. Hypotheses derived from comparative analysis will be tested by repression and mis-expression of candidate genes in transgenic Arabidopsis and Moricandia spec.