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bioRxiv · 10.1101/2024.12.19.629515

The Arabidopsis 14-3-3 proteins positively regulate brassinosteroid signaling by stabilizing BRASSINOSTEROID INSENSITIVE1 at the plasma membrane

Liu, D.
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Abstract

Brassinosteroid (BR) hormones regulate various physiological and developmental processes in plants. BR signaling is primarily influenced by the plasma membrane abundance of the BR receptor BR INSENSITIVE1 (BRI1), a process regulated by ubiquitination, endocytosis, and protein degradation. Despite extensive research, only a few negative regulators of BRI1 internalization and ubiquitination have been identified. In this study, we show that the conserved eukaryotic regulatory proteins 14-3-3 directly interact with BRI1 at Threonine 872 (T872) within its juxtamembrane domain. Furthermore, phosphorylation at Serine 858 (S858) in BRI1s juxtamembrane domain enhances T872 phosphorylation, facilitating 14-3-3 protein binding. Consequently, by inhibiting BRI1 ubiquitination without affecting its kinase activity or BAK1 interaction, 14-3-3 binding increased BRI1 plasma membrane abundance and enhanced BR signaling. Both non-epsilon and epsilon isoforms of 14-3-3 proteins contribute to the regulation of BRI1 and, consequently, to plant responsiveness to BRs. Our results revealed a previously undescribed function of 14-3-3 proteins in regulating BRI1 stability. One Sentence Summary14-3-3s stabilize BRI1 by antagonizing its ubiquitination

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Liu, D.. 2024-12-20. The Arabidopsis 14-3-3 proteins positively regulate brassinosteroid signaling by stabilizing BRASSINOSTEROID INSENSITIVE1 at the plasma membrane. https://doi.org/10.1101/2024.12.19.629515

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