Rubisco catalytic adaptation is mostly driven by photosynthetic conditions - Not by phylogenetic constraints

The prevalence of phylogenetic constraints in Rubisco evolution has been emphasised recently by (Bouvier et al., 2021), who argued that phylogenetic inheritance limits Rubisco adaptation much more than the biochemical trade-off between specificity, CO₂ affinity and turn-over. In this Opinion, we have critically examined how a phylogenetic signal can be computed with Rubisco kinetic properties and phylogenetic trees, and we arrive at a different conclusion. In particular, Rubisco's adaptation is partly driven by C₄ vs. C₃ photosynthetic conditions in Angiosperms, apparent phylogenetic signals being mostly due to either homoplasy, computation artefacts or the use of nearly identical sister species. While phylogenetic inheritance of an ancestral enzyme form probably has some role in Rubisco's adaptation landscape, it is a minor player, at least compared to microenvironmental conditions such as CO₂ and O₂ concentrations.