The Arabidopsis CERK 1‐associated kinase PBL 27 connects chitin perception to MAPK activation

Abstract

Perception of microbe‐associated molecular patterns by host cell surface pattern recognition receptors (PRRs) triggers the intracellular activation of mitogen‐activated protein kinase (MAPK) cascades. However, it is not known how PRRs transmit immune signals to MAPK cascades in plants. Here, we identify a complete phospho‐signaling transduction pathway from PRR‐mediated pathogen recognition to MAPK activation in plants. We found that the receptor‐like cytoplasmic kinase PBL27 connects the chitin receptor complex CERK1‐LYK5 and a MAPK cascade. PBL27 interacts with both CERK1 and the MAPK kinase kinase MAPKKK5 at the plasma membrane. Knockout mutants of MAPKKK5 compromise chitin‐induced MAPK activation and disease resistance to Alternaria brassicicola. PBL27 phosphorylates MAPKKK5 in vitro, which is enhanced by phosphorylation of PBL27 by CERK1. The chitin perception induces disassociation between PBL27 and MAPKKK5 in vivo. Furthermore, genetic evidence suggests that phosphorylation of MAPKKK5 by PBL27 is essential for chitin‐induced MAPK activation in plants. These data indicate that PBL27 is the MAPKKK kinase that provides the missing link between the cell surface chitin receptor and the intracellular MAPK cascade in plants.

Receptor Kinases in Plant-Pathogen Interactions: More Than Pattern Recognition

“…Paradoxically, MAPKKK5 appears to negatively impact flg22-triggered MPK activation. MAPKKK5 activation was shown to activate MKK4 and MKK5, which is consistent with the activation of MPK3 and MPK6 (Yamada et al, 2016b). The finding that PBL27 directly links a PRR to MPK activation is potentially exciting.…”

“…These results suggest differential contribution of RLCK family members to MPK activation by different patterns. Recently, MAPKKK5 was reported to be a specific substrate of PBL27 and mediate chitin-triggered MPK activation (Yamada et al, 2016b). Paradoxically, MAPKKK5 appears to negatively impact flg22-triggered MPK activation.…”

“…Recently, P. syringae was found to deliver a novel protease called HopB1 to destroy BAK1 (Li et al, 2016c). Perturbation of BAK1 is known to trigger the plant surveillance system and elevates defenses (Yamada et al, 2016b). Surprisingly, HopB1 goes undetected during infection (Li et al, 2016c).…”

From Chaos to Harmony: Responses and Signaling upon Microbial Pattern Recognition

“…It is possible that distinct phosphorylation by BIK1 and PBL13 results in opposing activities of RBOHD or that the different interacting partners of BIK1 and PBL13 contribute to the differential regulations of RBOHD. Although loss-of-function of BIK1 and PBL1 does not significantly compromise flg22- or elf18-triggered MAPK activation, CERK1-activated PBL27 directly phosphorylates and activates a MAPK cascade consisting of MAPKKK5-MKK4/5-MPK3/6 in chitin-triggered signaling in Arabidopsis (162). Additional RLCK targets are likely involved in transducing signals into diverse intracellular outputs.…”

The Monocot-Specific Receptor-like Kinase SDS2 Controls Cell Death and Immunity in Rice

“…PRR perception induces immune signaling that branches into ROS production and MAPK cascades via different receptor-like cytoplasmic kinases (RLCKs). For example, RLCK AtBIK1/AtPBL1 directly transmit AtFLS2/AtEFR signals to AtRbohD to produce ROS, while AtPBL27 links CERK1 to MAPKKK5, which activates the MAPK cascade to induce PR gene expression (Kadota et al, 2014; Li et al, 2014; Yamada et al, 2016). For attenuation of PTI, FLS2 is ubiquitinated by the U-box E3 ligases PUB12/13 for degradation (Lu et al, 2011).…”