The pyrenoidal linker protein EPYC1 phase separates with hybrid Arabidopsis-Chlamydomonas Rubisco through interactions with the algal Rubisco small subunit
Date
2019
Authors
Sharwood, Robert
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Publisher
Oxford University Press
Abstract
Photosynthetic efficiencies in plants are restricted by the CO2-fixing enzyme Rubisco but could be enhanced by introducing a CO2-concentrating mechanism (CCM) from green algae, such as Chlamydomonas reinhardtii (hereafter Chlamydomonas). A key feature of the algal CCM is aggregation of Rubisco in the pyrenoid, a liquid-like organelle in the chloroplast. Here we have used a yeast two-hybrid system and higher plants to investigate the protein-protein interaction between Rubisco and essential pyrenoid component 1 (EPYC1), a linker protein required for Rubisco aggregation. We showed that EPYC1 interacts with the small subunit of Rubisco (SSU) from Chlamydomonas and that
EPYC1 has at least five SSU interaction sites. Interaction is crucially dependent on the two surface-exposed α-helices
of the Chlamydomonas SSU. EPYC1 could be localized to the chloroplast in higher plants and was not detrimental
to growth when expressed stably in Arabidopsis with or without a Chlamydomonas SSU. Although EPYC1 interacted with Rubisco in planta, EPYC1 was a target for proteolytic degradation. Plants expressing EPYC1 did not show obvious evidence of Rubisco aggregation. Nevertheless, hybrid Arabidopsis Rubisco containing the Chlamydomonas SSU could phase separate into liquid droplets with purified EPYC1 in vitro, providing the first evidence of pyrenoidlike aggregation for Rubisco derived from a higher plant.
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Keywords
Arabidopsis thaliana, Chlamydomonas reinhardtii, chloroplast, CO2-concentrating mechanism, Nicotiana benthamiana, photosynthesis, pyrenoid
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Journal of Experimental Botany
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Journal article
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Open Access
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Creative Commons Attribution Non-Commercial License
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