Mechanistic Insights into the Function of 14-3-3 Proteins as Negative Regulators of Brassinosteroid Signaling in Arabidopsis

• DOI: 10.1093/pcp/pcae056
• Publication Date: 2024-05-24T03:57:35Z
• Authors: Elsa Obergfell; Ulrich Hohmann; Andrea Moretti; Houming Chen; Michael Hothorn
• Keywords: Brassinosteroid; Phosphopeptide

Abstract Brassinosteroids (BRs) are vital plant steroid hormones sensed at the cell surface by a membrane signaling complex comprising receptor kinase BRI1 and SERK family co-receptor kinase. Activation of this lead to dissociation inhibitor protein BKI1 from differential phosphorylation BZR1/BES1 transcription factors glycogen synthase 3 BIN2. Many phosphoproteins BR pathway, including BRI1, SERKs, can associate with 14-3-3 proteins. In study, we use quantitative ligand binding assays define minimal sites in N-terminal lobe domain, BKI1, BZR1 Arabidopsis thaliana. All three motifs require be phosphorylated specifically bind 14-3-3s mid- low-micromolar affinity. components display isoform preference within non-ε subgroup. 14-3-3λ ω crystal structures reveal that as canonical type II linear motifs. Disruption key amino acids phosphopeptide site through mutation impairs interaction all Notably, quadruple loss-of-function mutants group exhibit gain-of-function phenotypes, suggesting role for proteins overall negative regulators pathway. Collectively, our work provides further mechanistic genetic evidence regulatory various stages cascade.