The chloroplast proteome contains thousands of different proteins that are encoded by the nuclear genome. These proteins are imported into the chloroplast via the action of the TOC translocase and associated downstream systems. Our recent work has revealed that the stability of the TOC complex is dynamically regulated by the ubiquitin-dependent chloroplast-associated protein degradation (CHLORAD) pathway. Here, we demonstrate that the TOC complex is also regulated by the SUMO system. Arabidopsis mutants representing almost the entire SUMO conjugation pathway can partially suppress the phenotype of ppi1, a pale-yellow mutant lacking the Toc33 protein. This suppression is linked to increased abundance of TOC proteins and improvements in chloroplast development. Moreover, data from molecular and biochemical experiments support a model in which the SUMO system directly regulates TOC protein stability. Thus, we have identified a regulatory link between the SUMO system and the chloroplast protein import machinery.
All data generated or analysed during this study are included in the manuscript and supporting files.
- R Paul Jarvis
- Samuel Watson
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
- Heather E McFarlane, University of Toronto, Canada
- Received: July 11, 2020
- Accepted: September 1, 2021
- Accepted Manuscript published: September 2, 2021 (version 1)
© 2021, Watson et al.
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