Effects of Arabidopsis wall associated kinase mutations on ESMERALDA1 and elicitor induced ROS.

Bruce D Kohorn,Stéphane Verger,Bridgid E Greed,Gregory Mouille,Susan L Kohorn,Olga A Zabotina

doi:10.1371/journal.pone.0251922

Abstract

Angiosperm cell adhesion is dependent on interactions between pectin polysaccharides which make up a significant portion of the plant cell wall. Cell adhesion in Arabidopsis may also be regulated through a pectin-related signaling cascade mediated by a putative O-fucosyltransferase ESMERALDA1 (ESMD1), and the Epidermal Growth Factor (EGF) domains of the pectin binding Wall associated Kinases (WAKs) are a primary candidate substrate for ESMD1 activity. Genetic interactions between WAKs and ESMD1 were examined using a dominant hyperactive allele of WAK2, WAK2cTAP, and a mutant of the putative O-fucosyltransferase ESMD1. WAK2cTAP expression results in a dwarf phenotype and activation of the stress response and reactive oxygen species (ROS) production, while esmd1 is a suppressor of a pectin deficiency induced loss of adhesion. Here we find that esmd1 suppresses the WAK2cTAP dwarf and stress response phenotype, including ROS accumulation and gene expression. Additional analysis suggests that mutations of the potential WAK EGF O-fucosylation site also abate the WAK2cTAP phenotype, yet only evidence for an N-linked but not O-linked sugar addition can be found. Moreover, a WAK locus deletion allele has no effect on the ability of esmd1 to suppress an adhesion deficiency, indicating WAKs and their modification are not a required component of the potential ESMD1 signaling mechanism involved in the control of cell adhesion. The WAK locus deletion does however affect the induction of ROS but not the transcriptional response induced by the elicitors Flagellin, Chitin and oligogalacturonides (OGs).

Highlights

Cell adhesion in plants is dependent on pectin polysaccharides which comprise a major portion of the immediate interface between cells [1, 2]
The ability of the cell wall to compensate for reduced pectin content and still demonstrate proper adhesion points to the existence of an undefined signaling mechanism [22]
As Wall associated Kinases (WAKs) are receptor kinases and have the ability to bind to both wall pectin and short pectin fragments known as oligogalacturonides (OGs), WAKs serve as a prime candidate for this pectin signaling cascade [40]

Summary

Introduction

Cell adhesion in plants is dependent on pectin polysaccharides which comprise a major portion of the immediate interface between cells [1, 2]. Mutations in ESMD1 can suppress qua and frb yet there is no restoration of pectin levels [22] The nature of this putative signaling pathway is not known, but clues to its identity may lie in the plant receptor kinases that contain an EGF domain. The family of 6, G-type lectin S-receptor-like serine/threonine-protein kinase each have one EGF domain with a O-fucosylation consensus sequence. The pectin binding Wall associated Kinases (WAKs) contain a potential ESMD1 substrate and since there is ample evidence that WAKs are involved in pectin signaling [27,28,29,30,31,32], they are a primary candidate for ESMD1 mediated O-fucosylation. A new 25 Kb deletion was created in the locus that contains the 5 WAKs and this revealed that WAKs play a role in the ROS response to multiple elicitors

Materials and methods

Results

Findings

Discussion