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Transport-coupled ubiquitination of the borate transporter BOR1 for its boron-dependent degradation.

ABSTRACT: Plants take up and translocate nutrients through transporters. In Arabidopsis thaliana, the borate exporter BOR1 acts as a key transporter under boron (B) limitation in the soil. Upon sufficient-B supply, BOR1 undergoes ubiquitination and is transported to the vacuole for degradation, to avoid overaccumulation of B. However, the mechanisms underlying B-sensing and ubiquitination of BOR1 are unknown. In this study, we confirmed the lysine-590 residue in the C-terminal cytosolic region of BOR1 as the direct ubiquitination site and showed that BOR1 undergoes K63-linked polyubiquitination. A forward genetic screen identified that amino acid residues located in vicinity of the substrate-binding pocket of BOR1 are essential for the vacuolar sorting. BOR1 variants that lack B-transport activity showed a significant reduction of polyubiquitination and subsequent vacuolar sorting. Coexpression of wild-type (WT) and a transport-defective variant of BOR1 in the same cells showed degradation of the WT but not the variant upon sufficient-B supply. These findings suggest that polyubiquitination of BOR1 relies on its conformational transition during the transport cycle. We propose a model in which BOR1, as a B transceptor, directly senses the B concentration and promotes its own polyubiquitination and vacuolar sorting for quick and precise maintenance of B homeostasis.

SUBMITTER: Yoshinari A

PROVIDER: S-EPMC8136889 | biostudies-literature |

REPOSITORIES: biostudies-literature

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High boron-induced ubiquitination regulates vacuolar sorting of the BOR1 borate transporter in Arabidopsis thaliana.

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ATR1 Boron Transporter is Regulated by Gcn4 Transcription Factor in Response to Boron Stress

Project description:Transcriptional profiling of yeast wild type BY4741, gcn4 and yap1 mutants in response to boron treatment. Transcriptional profiling of yeast wild type BY4741, gcn4 and yap1 mutants in response to boron treatment.

2011-07-19 | E-GEOD-29887 | biostudies-arrayexpress

Tolerance to Excess-Boron Conditions Acquired by Stabilization of a BOR1 Variant with Weak Polarity in Arabidopsis.

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