Plants and algae fix carbon through photosynthesis, which converts CO2 to organic carbon. This biological process is catalyzed by the Rubisco enzyme, the most abundant protein on Earth.

Low-Res_p20240229140000

Source: University of Tsukuba

Pyrenoids labeled by GFP (green) and chlorophyll fluorescence (magenta)

In many algae, Rubisco is densely packed into a microcompartment called the pyrenoid, which plays an important role in the CO2 accumulation in aquatic environments. Notably, approximately one-third of global carbon fixation is estimated to occur within algal pyrenoids. Apart from Rubisco, the primary component of pyrenoids, the pyrenoid-associated proteins in most algae remain unclarified.

Convergent evolution

In this study, pyrenoid-associated proteins in a marine chlorarachniophyte alga were identified through a proteomic approach. Some of these proteins are apparently involved in pyrenoid construction and CO2 concentration. Interestingly, various pyrenoid-associated proteins have been reported among the algae studied to date, suggesting that CO2-fixing organelles evolved independently in each algal group. This is an example of convergent evolution at the molecular level.

Genetic engineering of plants using algal genes is underway to increase the photosynthetic performance. The pyrenoid-associated proteins reported herein are a potential basis for improving crop productivity in the future.

This work was funded by the Japan Society for the Promotion of Science (JSPS) KAKENHI Grant Numbers 18K06358 and 21K06285, and by the Institute for Fermentation, Osaka (LA-2022-011).

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