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bioRxiv · 10.1101/2022.06.06.494369

Ubiquitin-based pathway acts inside chloroplasts to regulate photosynthesis

Sun, Y.·Yao, Z.·Chen, H.·Ye, Y.·Lyu, Y.·Broad, W.·Fournier, M.·Chen, G.·Hu, Y.·Mohammed, S.·Ling, Q.·Jarvis, R. P.
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Abstract

Photosynthesis is the energetic basis for most life on Earth, and in plants it operates inside double-membrane-bound organelles called chloroplasts. The photosynthetic apparatus comprises numerous proteins encoded by the nuclear and organellar genomes. Maintenance of this apparatus requires the action of internal chloroplast proteases, but a role for the nucleocytosolic ubiquitin-proteasome system (UPS) was not expected owing to the barrier presented by the double-membrane envelope. Here, we show that photosynthesis proteins (including those encoded internally by chloroplast genes) are ubiquitinated, and processed via the CHLORAD pathway: they are degraded by the 26S proteasome following CDC48-dependent retrotranslocation to the cytosol. This demonstrates that the reach of the UPS extends to the interior of endosymbiotically-derived chloroplasts, where it acts to regulate one of the most fundamental processes of life. One Sentence SummaryThe ubiquitin-proteasome system targets proteins inside chloroplasts, including chloroplast-encoded photosynthesis subunits.

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Sun, Y., Yao, Z., Chen, H., Ye, Y., Lyu, Y., Broad, W., Fournier, M., Chen, G., Hu, Y., Mohammed, S., Ling, Q., Jarvis, R. P.. 2022-06-06. Ubiquitin-based pathway acts inside chloroplasts to regulate photosynthesis. https://doi.org/10.1101/2022.06.06.494369

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