Characterization of BRASSINOSTEROID F-BOX Proteins BRFPs that Regulate BRASSINOSTEROID-INSENSITIVE 2 Kinase

BRASSINOSTEROIDS (BRs) play important roles in regulating plant growth and development. The Arabidopsis GSK3-like kinase BIN2, a major negative regulator of BR signaling, plays diverse roles in plant growth and developmental processes. In a previous study, based on the relationship between BIN2 and its substrate, we reported the possibility that BIN2 protein stability is controlled by BRASSINOSTEROID F-BOX Protein 1 and 2, BRF1 and BRF2, (BRF1/2, renamed BRFP1/2). The aim of the study was to characterize the functions of the F-box proteins BRFP1 and BRFP2, and to confirm their relationship with the BIN2 proteins and the role of the BR signaling for plant growth and development. BRFP1-overexpressing (BRFP1-FLAG) plants displayed better growth compared to the wild-type Col-0 plants in contrast to brfp1/2 mutants. BRFP1 plants were sensitive to BL, the most active BR, as opposed to the brfp1/2 mutants. We confirmed that BRFP1 overexpression suppressed the dwarf BIN2-HA phenotype by reducing BIN2 protein levels through BRFP1-BIN2 interactions in vivo. These results suggest the possibility that the stability of BIN2 is regulated by BRFP1. Altogether, results of our finding propose that the F-box proteins BRFP1/2 are involved in BR signaling for regulating plant growth.

Automated summary

The study found that BRFP1 and BRFP2 are involved in the BR signaling pathway, affecting plant growth and development by regulating the stability of BIN2 protein.