An unconventional Rubisco small subunit underpins the CO(2)-concentrating organelle in land plants
Summary
In many algae, photosynthesis is boosted by biophysical CO2-concentrating mechanisms, which pack the CO2-fixing enzyme Rubisco into liquid-like organelles called pyrenoids. Engineering C3 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 t
Content
# An unconventional Rubisco small subunit underpins the CO(2)-concentrating organelle in land plants
*Published: 2026 Mar 5*
In many algae, photosynthesis is boosted by biophysical CO2-concentrating
mechanisms, which pack the CO2-fixing enzyme Rubisco into liquid-like organelles
called pyrenoids. Engineering C3 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.
DOI: 10.1126/science.aea0150