The Receptor-like Cytoplasmic Kinase BIK1 Localizes to the Nucleus and Regulates Defense Hormone Expression during Plant Innate Immunity

Publication date: 11 April 2018
Source:Cell Host & Microbe, Volume 23, Issue 4
Author(s): Neeraj K. Lal, Ugrappa Nagalakshmi, Nicholas K. Hurlburt, Rosalva Flores, Aurelie Bak, Pyae Sone, Xiyu Ma, Gaoyuan Song, Justin Walley, Libo Shan, Ping He, Clare Casteel, Andrew J. Fisher, Savithramma P. Dinesh-Kumar
Plants employ cell-surface pattern recognition receptors (PRRs) to detect pathogens. Although phytohormones produced during PRR signaling play an essential role in innate immunity, a direct link between PRR activation and hormone regulation is unknown. EFR is a PRR that recognizes bacterial EF-Tu and activates immune signaling. Here we report that EFR regulates the phytohormone jasmonic acid (JA) through direct phosphorylation of a receptor-like cytoplasmic kinase, BIK1. The BIK1 structure revealed that the EFR-phosphorylated sites reside on a uniquely extended loop away from the BIK1 kinase core domain. Phosphomimetic mutations of these sites resulted in increased phytohormones and enhanced resistance to bacterial infections. In addition to its documented plasma membrane localization, BIK1 also localizes to the nucleus and interacts directly with WRKY transcription factors involved in the JA and salicylic acid (SA) regulation. These findings demonstrate the mechanistic basis of signal transduction from PRR to phytohormones, mediated through a PRR-BIK1-WRKY axis.

Graphical abstract

Teaser

Receptor-like cytoplasmic kinases (RLCKs) function at the plasma membrane during plant pattern recognition receptor (PRR)-mediated immunity. Lal et al. show that the RLCK BIK1 is uniquely phosphorylated by the PRR EFR and localizes to the nucleus where it interacts with WRKY transcription factors to regulate defense hormones during plant immunity.


https://ift.tt/2Hi2gAs