The role of N-myristoylation in homeostasis of brassinosteroid signaling kinase 1.

The N-myristoylation is required for BSK1 proper plasma membrane targeting and protein turnover. Brassinosteroid (BR) signaling kinase 1 (BSK1), with a myristoylation site at its N-terminus to anchor at plasma membrane (PM), is involved in BR-regulated plant growth and flg22-triggered immunity responses. However, little is known about the role of N-myristoylation in BSK1 protein homeostasis. Here, we revealed that N-myristoylation is critical to the PM targeting and protein stability of BSK1. The N-myristoylation-deficient mutant BSK1 mainly distributed in the cytoplasm and retained in the endoplasmic reticulum. We further found that the BSK1 proteins were unstable and degraded through ATG8e-labled autophagic pathway. This study provides a new insight into the regulation of plant protein homeostasis.