Fig. 8: Proposed engineering path for installing a minimal PCCM into land plants.

a, Top: schematics of the starting configuration representing a typical plant chloroplast that contains diffuse thylakoid carbonic anhydrase, diffuse stromal carbonic anhydrase, and diffuse Rubisco, and lacks HCO₃⁻ transporters and diffusion barriers. Bottom: the desired configuration representing a Chlamydomonas chloroplast that employs the passive CO₂ uptake strategy and a starch sheath (as in Fig. 2g). b, Venn diagram showing the normalized CO₂ fixation flux (circle, area in proportion to magnitude) and ATP spent per CO₂ fixed (square, area in proportion to magnitude) of various configurations after implementing the designated changes. Arrows denote the proposed sequential steps to transform the starting configuration into the desired configuration (see text). The starting configuration has a normalized CO₂ fixation flux of 0.31 and negligible ATP cost. All costs below 0.25 ATP per CO₂ fixed are represented by a square of the minimal size.