SUMO/deSUMOylation of the BRI1 brassinosteroid receptor modulates plant growth responses to temperature

Brassinosteroids (BRs) are a class of steroid molecules perceived at the cell surface that act as plant hormones. The BR receptor BRASSINOSTEROID INSENSITIVE1 (BRI1) offers a model to understand receptor-mediated signaling in plants and the role of post-translational modifications. Here we identify SUMOylation as a new modifi-cation targeting BRI1 to regulate its activity. BRI1 is SUMOylated in planta on two lysine residues, and the levels of BRI1 SUMO conjugates are controlled by the Desi3a SUMO protease. Loss of Desi3a leads to hypersensitivity to BRs, indicating that Desi3a acts as a negative regulator of BR signaling. Besides, we demonstrate that BRI1 is deS-UMOylated at elevated temperature by Desi3a, leading to increased BRI1 interaction with the negative regulator of BR signaling BIK1 and to enhanced BRI1 endocytosis. Loss of Desi3a or BIK1 results in increased response to temperature elevation, indicating that BRI1 deSUMOylation acts as a safety mechanism necessary to keep temperature responses in check. Altogether, our work establishes BRI1 deSUMOylation as a molec-ular crosstalk mechanism between temperature and BR signaling, allowing plants to translate environmental inputs into growth response.

Automated summary

This study reveals that the plant hormone receptor BRI1 is regulated by SUMOylation and its activity is controlled by the SUMO protease Desi3a. Moreover, Desi3a regulates the interaction between BRI1 and the negative regulator BIK1 as well as BRI1 endocytosis. The deSUMOylation of BRI1 by Desi3a is proposed as a molecular crosstalk mechanism between temperature and BR signaling, enabling plants to respond to environmental inputs.