SUMOylation contributes to proteostasis of the chloroplast protein import receptor TOC159 during early development
- Université de Neuchâtel, Switzerland
Abstract
Chloroplast biogenesis describes the transition of non-photosynthetic proplastids to photosynthetically active chloroplasts in the cells of germinating seeds. Chloroplast biogenesis requires the import of thousands of nuclear-encoded preproteins by essential import receptor TOC159. We demonstrate that the SUMO (Small Ubiquitin-related Modifier) pathway crosstalks with the ubiquitin-proteasome pathway to affect TOC159 stability during early plant development. We identified a SUMO3-interacting motif (SIM) in the TOC159 GTPase domain and a SUMO3 covalent SUMOylation site in the membrane domain. A single K to R substitution (K1370R) in the M-domain disables SUMOylation. Compared to wild type TOC159, TOC159K1370R was destabilized under UPS-inducing stress conditions. However, TOC159K1370R recovered to same protein level as wild type TOC159 in the presence of a proteasome inhibitor. Thus, SUMOylation partially stabilizes TOC159 against UPS-dependent degradation under stress conditions. Our data contribute to the evolving model of tightly controlled proteostasis of the TOC159 import receptor during proplastid to chloroplast transition.
Data availability
All data generated or analysed during this study are included in the manuscript and supporting files. Source data files have been provided for Figures 2 and 3.
Article and author information
Author details
Venkatasalam Shanmugabalaji
Funding
Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung (31003A_156998)
- Felix Kessler
Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung (31003A _176191)
- Felix Kessler
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2020, Accossato et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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SUMOylation contributes to proteostasis of the chloroplast protein import receptor TOC159 during early development
eLife 9:e60968.
https://doi.org/10.7554/eLife.60968
Further reading
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- Plant Biology
Urea is intensively utilized as a nitrogen fertilizer in agriculture, originating either from root uptake or from catabolism of arginine by arginase. Despite its extensive use, the underlying physiological mechanisms of urea, particularly its adverse effects on seed germination and seedling growth under salt stress, remain unclear. In this study, we demonstrate that salt stress induces excessive hydrolysis of arginine-derived urea, leading to an increase in cytoplasmic pH within seed radical cells, which, in turn, triggers salt-induced inhibition of seed germination (SISG) and hampers seedling growth. Our findings challenge the long-held belief that ammonium accumulation and toxicity are the primary causes of SISG, offering a novel perspective on the mechanism underlying these processes. This study provides significant insights into the physiological impact of urea hydrolysis under salt stress, contributing to a better understanding of SISG.
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- Plant Biology
Salt stress delays seed germination in plants by increasing the hydrolysis of arginine-derived urea.
