Data from: Independent and parallel evolution of new genes by gene duplication in two origins of C4 photosynthesis provides new insight into the mechanism of phloem loading in C4 species

C4 photosynthesis is considered one of the most remarkable examples of evolutionary convergence in eukaryotes. However, it is unknown whether the evolution of C4 photosynthesis required the evolution of new genes. Genome-wide gene-tree species-tree reconciliation of seven monocot species that span two origins of C4 photosynthesis revealed that there was significant parallelism in the duplication and retention of genes coincident with the evolution of C4 photosynthesis in these lineages. Specifically, 21 orthologous genes were duplicated and retained independently in parallel at both C4 origins. Analysis of this gene cohort revealed that the set of parallel duplicated and retained genes is enriched for genes that are preferentially expressed in bundle sheath cells, the cell type in which photosynthesis was activated during C4 evolution. Furthermore, functional analysis of the cohort of parallel duplicated genes identified SWEET-13 as a potential key transporter in the evolution of C4 photosynthesis in grasses, and provides new insight into the mechanism of phloem loading in these C4 species.C4光合作用（C4 photosynthesis）被认为是真核生物（eukaryotes）中最显著的进化趋同实例之一。然而目前仍未明确，C4光合作用的演化是否需要全新基因的演化。针对包含两次C4光合作用独立起源事件的7个单子叶植物物种开展的全基因组基因树-物种树调和分析（genome-wide gene-tree species-tree reconciliation）显示，在这些演化支系中，与C4光合作用演化同步发生的基因复制与保留现象存在显著平行性。具体而言，有21个直系同源基因（orthologous genes）在两次C4起源事件中独立发生了平行的复制与保留。对该基因集合的分析表明，这类经平行复制并保留的基因显著富集于在维管束鞘细胞（bundle sheath cells）中偏好表达的基因——而维管束鞘细胞正是C4演化过程中光合作用被激活的细胞类型。此外，对该平行复制基因集合的功能分析鉴定出SWEET-13作为禾本科植物C4光合作用演化中的潜在关键转运蛋白，并为这类C4物种的韧皮部装载（phloem loading）机制提供了全新的研究视角。