A research conducted at the Institute of Genetics and Development Biology of the Chinese Academy of Sciences (CAS) led by Zhou Jianmin has discovered how plants use a sophisticated mechanism to accurately control immune responses. The research team previously found that a protein kinase called BIK1 is a central player that relays signals from multiple immune receptors to different cellular defenses. BIK1 is a rate-limiting component, whose phosphorylation and accumulation are central to immune signal propagation. In the study, they show that a pair of ubiquitin E3 ligases, PUB25 and PUB26, that are responsible for adding poly-ubiquitin chains to BIK1, and both CPK28 and the heterotrimeric G proteins regulate BIK1 stability through PUB25/26. In the resting state, the immune receptors and BIK1 are not activated, and plant immunity is regulated as heterotrimeric G proteins that directly inhibit PUB25/26 E3 activity to stabilize BIK1. (Source: Crop Biotech Update, International Service for Acquisition of Agri-Biotech Applications. www.isaaa.org)
Model for the PUB25/26-mediated control of BIK1 homeostasis. Photo Credit: IGDB