Submerged angiosperms sustain some of the most productive and diverse ecosystems worldwide. However, their carbon acquisition and assimilation mechanisms remain poorly explored, missing an important step in the evolution of photosynthesis during the colonization of aquatic environments by angiosperms. Here we reveal a convergent kinetic adaptation of Rubisco in phylogenetically distant seagrass species that share catalytic efficiencies and CO₂ and O₂ affinities up to three times lower than those observed in phylogenetically closer angiosperms from terrestrial, freshwater and brackish-water habitats. This Rubisco kinetic convergence was found to correlate with the effectiveness of seagrass CO₂-concentrating mechanisms (CCMs), which probably evolved in response to the constant CO₂ limitation in marine environments. The observed Rubisco kinetic adaptation in seagrasses more closely resembles that seen in eukaryotic algae operating CCMs rather than that reported in terrestrial C₄ plants. Our results thus demonstrate a general pattern of co-evolution between Rubisco function and biophysical CCM effectiveness that traverses distantly related aquatic lineages.

淹没的被子植物维持着世界上一些最具生产力和多样化的生态系统。然而，它们的碳获取和同化机制仍然缺乏探索，在被子植物在水生环境中定殖期间，缺少光合作用进化的重要一步。在这里，我们揭示了 Rubisco 在系统发育上较远的海草物种中的收敛动力学适应，其催化效率和 CO ₂和 O ₂亲和力比在来自陆地、淡水和咸水生境的系统发育上更接近的被子植物中观察到的低三倍。发现这种 Rubisco 动力学收敛与海草 CO _{2的有效性相关}-浓缩机制（CCM），可能是响应海洋环境中恒定的CO _{2限制而演变的。}在海草中观察到的 Rubisco 动力学适应更类似于在操作 CCM 的真核藻类中看到的，而不是在陆地 C ₄植物中报道的。因此，我们的研究结果证明了 Rubisco 功能和生物物理 CCM 有效性之间共同进化的一般模式，该模式跨越了远缘相关的水生谱系。