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Development of chloroplasts and other plastids depends on the import of thousands of nucleus-encoded proteins from the cytosol. Import is initiated by TOC (translocon at the outer envelope of chloroplasts) complexes in the plastid outer membrane that incorporate multiple, client-specific receptors. Modulation of import is thought to control the plastid's proteome, developmental fate, and functions. Using forward genetics, we identified Arabidopsis SP1, which encodes a RING-type ubiquitin E3 ligase of the chloroplast outer membrane. The SP1 protein associated with TOC complexes and mediated ubiquitination of TOC components, promoting their degradation. Mutant sp1 plants performed developmental transitions that involve plastid proteome changes inefficiently, indicating a requirement for reorganization of the TOC machinery. Thus, the ubiquitin-proteasome system acts on plastids to control their development.

Original publication

DOI

10.1126/science.1225053

Type

Journal article

Journal

Science

Publication Date

02/11/2012

Volume

338

Pages

655 - 659

Keywords

Apoptosis Regulatory Proteins, Arabidopsis, Arabidopsis Proteins, Chloroplast Proteins, Chloroplasts, Membrane Proteins, Mutation, Proteasome Endopeptidase Complex, Protein Precursors, Protein Transport, Proteome, RING Finger Domains, Ubiquitin-Protein Ligases, Ubiquitination