518 / 2019-03-01 19:34:04

A Temperature-Sensitive Misfolded bri1-301 Receptor Requires Its Kinase Activity to Promote Growth

brassinosteroids,receptor-like kinase,protein misfolding,protein degradation,protein quality control

全体主题 > Hormones

Brassinosteroid (BR) signaling pathway plays an important role in the regulation of plant growth and development. BR receptor BRI1 (Brassinosteroid Insensitive 1) binds the extracellular BRs and activates an intracellular signaling pathway via its kinase activity. bri1-301 is a mutant BR receptor carrying the cytosolic Gly989-to-Ile mutation, which abolishes its kinase activity in vitro and decreases the BRI1 abundance. However, the bri1-301 mutant is a weak dwarf mutant compared to other strong bri1 alleles, raising a question whether or not the kinase activity of BRI1 is essential for its biological function. We found that the Gly989-Ile mutation significantly reduces the BR-triggered BRI1 phosphorylation in vivo and the mutant bri1-301 receptor requires its kinase activity to promote plant growth and development. We also discovered that bri1-301 is a temperature-sensitive misfolded protein that was degraded through unknown mechanisms in the endoplasmic reticulum and plasma membrane, and that bri1-301 mutant exhibits extremely severe dwarf phenotypes at high temperatures that greatly reduced the bri1-301 protein abundance. Further biochemical and genetic experiments suggested that higher temperatures likely exacerbate misfolding of the mutant BR receptor. Therefore, bri1-301 protein can be used as a model to study the protein quality control mechanisms that monitors misfolded proteins in the cytoplasm or plasma membrane.