State Key Laboratory for Plant Molecular Genetics, Center of Excellence for Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai 200032, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
Plant Physiol. 2022 Aug 29;190(1):441-458. doi: 10.1093/plphys/kiac252.
C4 photosynthesis optimizes plant carbon and water relations, allowing high photosynthetic rates with low stomatal conductance. Stomata have long been considered a part of the C4 syndrome. However, it remains unclear how stomatal traits evolved along the path from C3 to C4. Here, we examined stomata in the Flaveria genus, a model used for C4 evolutionary study. Comparative, transgenic, and semi-in vitro experiments were performed to study the molecular basis that underlies the changes of stomatal traits in C4 evolution. The evolution from C3 to C4 species is accompanied by a gradual rather than an abrupt change in stomatal traits. The initial change appears near the Type I intermediate stage. Co-evolution of the photosynthetic pathway and stomatal traits is supported. On the road to C4, stomata tend to be fewer in number but larger in size and stomatal density dominates changes in anatomical maximum stomatal conductance (gsmax). Reduction of FSTOMAGEN expression underlies decreased gsmax in Flaveria and likely occurs in other C4 lineages. Decreased gsmax contributes to the increase in intrinsic water-use efficiency in C4 evolution. This work highlights the stomatal traits in the current C4 evolutionary model. Our study provides insights into the pattern, mechanism, and role of stomatal evolution along the road toward C4.
C4 光合作用优化了植物的碳和水分关系，使植物在低气孔导度下仍能保持较高的光合速率。长期以来，气孔一直被认为是 C4 综合征的一部分。然而，目前仍不清楚气孔特征是如何沿着从 C3 到 C4 的途径进化的。在这里，我们研究了黄花属（Flaveria）植物的气孔，该属植物是 C4 进化研究的模式生物。我们通过比较、转基因和半体外实验来研究 C4 进化过程中气孔特征变化的分子基础。从 C3 到 C4 物种的进化伴随着气孔特征的逐渐变化，而不是突然变化。最初的变化似乎发生在 I 型中间阶段附近。光合作用途径和气孔特征的共同进化得到了支持。在 C4 进化的道路上，气孔的数量逐渐减少，但体积逐渐增大，气孔密度主导着解剖学最大气孔导度（gsmax）的变化。 Flaveria 中 FSTOMAGEN 表达的减少导致 gsmax 降低，这可能发生在其他 C4 谱系中。gsmax 的降低有助于 C4 进化中内在水分利用效率的提高。这项工作突出了当前 C4 进化模型中的气孔特征。我们的研究为沿着 C4 途径的气孔进化的模式、机制和作用提供了新的见解。
