In many algae, photosynthesis is boosted by biophysical CO 2 -concentrating mechanisms, which pack the CO 2 -fixing enzyme Rubisco into liquid-like organelles called pyrenoids. Engineering C 3 crops with algal pyrenoids could increase yields, but progress is hampered by the deep evolutionary divide between crops and algae. Here, we show that hornworts, the only land plants with pyrenoids, have an unusual Rubisco small subunit, RbcS-STAR, the C-terminal coiled-coil domain of which oligomerizes to mediate Rubisco condensation. RbcS-STAR is incorporated into the Rubisco holoenzyme and thus acts as an “innate” Rubisco linker. Expression of RbcS-STAR in pyrenoid-lacking species, including Arabidopsis , is sufficient to induce pyrenoid-like condensates. Our findings reveal a mechanism for Rubisco condensation and a potential route to introduce pyrenoids into crop plants.
Robison et al. (Thu,) studied this question.