C₄ plants are believed to have evolved from C₃ plants through various C₃–C₄ intermediate stages in which a photorespiration-dependent CO₂ concentration system known as C₂ photosynthesis operates. Genes involved in the C₄ cycle were thought to be recruited from orthologs present in C₃ species and developed cell-specific expression during C₄ evolution. To understand the process of establishing C₄ photosynthesis, we performed whole-genome sequencing and investigated expression and mesophyll- or bundle-sheath-cell-specific localization of phosphoenolpyruvate carboxylase (PEPC), NADP-malic enzyme (NADP-ME), pyruvate, orthophosphate dikinase (PPDK) in C₃, C₃–C₄ intermediate, C₄–like, and C₄ Flaveria species. While genome sizes vary greatly, the number of predicted protein-coding genes was similar among C₃, C₃–C₄ intermediate, C₄–like, and C₄ Flaveria species. Cell-specific localization of the PEPC, NADP-ME, and PPDK transcripts was insignificant or weak in C₃–C₄ intermediate species, whereas these transcripts were expressed cell-type specific in C₄–like species. These results showed that elevation of gene expression and cell-specific control of pre-existing C₄ cycle genes in C₃ species was involved in C₄ evolution. Gene expression was gradually enhanced during C₄ evolution, whereas cell-specific control was gained independently of quantitative transcriptional activation during evolution from C₃–C₄ intermediate to C₄ photosynthesis in genus Flaveria.

中文翻译：

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黄花属C4进化过程中基因组大小的动态变化和C4酶细胞特异性分布的逐渐增加

据信，C ₄植物是从C ₃植物进化而来的，经过各种C ₃ -C ₄中间阶段，在该中间阶段，称为C ₂光合作用的依赖于光呼吸的CO ₂浓度系统在运行。参与 C ₄循环的基因被认为是从 C ₃物种中存在的直向同源物中募集的，并在 C ₄进化过程中发展出细胞特异性表达。了解建立C ₄的过程光合作用，我们进行了全基因组测序并研究了磷酸烯醇丙酮酸羧化酶 (PEPC)、NADP-苹果酸酶 (NADP-ME)、丙酮酸、正磷酸二激酶 (PPDK) 在 C _{3 中的}表达和叶肉或束鞘细胞特异性定位、C ₃ –C ₄中间体、C ₄样和C ₄ Flaveria物种。虽然基因组大小差异很大，但预测的蛋白质编码基因的数量在 C ₃、C ₃ -C ₄中间体、C ₄ -like 和 C ₄ Flaveria 中相似物种。PEPC、NADP-ME 和 PPDK 转录物的细胞特异性定位在 C ₃ -C ₄中间物种中微不足道或微弱，而这些转录物在 C ₄样物种中表达为细胞类型特异性。这些结果表明，C ₃物种中预先存在的C ₄循环基因的基因表达升高和细胞特异性控制参与了C ₄进化。在 C ₄进化过程中基因表达逐渐增强，而在从 C ₃ -C ₄中间体到 C ₄进化过程中，细胞特异性控制独立于定量转录激活获得光合作用属黄顶菊。