Photoregulatory Protein Kinases Fine-tune Plant Photomorphogenesis by Directing a Bifunctional Phospho-code on HY5

ABSTRACT: The core regulatory mechanisms affecting the function of ELONGATED HYPOCOTYL 5 (HY5) during plant photomorphogenesis include dynamics in the transcriptional activity and protein stability of HY5 in response to changes in ambient light; however, little is known about the mediators of these processes. Here, we identified PHOTOREGULATORY PROTEIN KINASE 1 (PPK1), which interacts directly with and phosphorylates HY5, as one such mediator. PPK1 and its homologs play redundant roles in the negative regulation of photomorphogenesis. PPK1 phosphorylates HY5 at Thr55, Ser56, and Ser60. The phosphorylation of these residues is essential to establish high-affinity binding with B-BOX PROTEIN 24 and CONSTITUTIVE PHOTOMORPHOGENIC 1, which inhibit the transcriptional activity and promote the ubiquitination and degradation of HY5, respectively. As such, PPKs regulate not only the binding of HY5 to its target genes under light conditions,but also HY5 degradation when plants are transferred from light to dark conditions. Our data reveal a PPK-mediated phospho-code on HY5 that integrates the molecular mechanisms underlying the regulation of HY5 transcriptional activity and protein stability to precisely control plant photomorphogenesis.

ORGANISM(S): Arabidopsis Thaliana

SUBMITTER: Shengwei Zhang  

PROVIDER: PXD049266 | iProX | Wed Feb 07 00:00:00 GMT 2024

REPOSITORIES: iProX