Activation of Defense Response Pathways by OGs and Flg22 Elicitors in Arabidopsis Seedlings

Abstract

We carried out transcriptional profiling analysis in 10-d-old Arabidopsis thaliana seedlings treated with oligogalacturonides (OGs), oligosaccharides derived from the plant cell wall, or the bacterial flagellin peptide Flg22, general elicitors of the basal defense response in plants. Although detected by different receptors, both OGs and Flg22 trigger a fast and transient response that is both similar and comprehensive, and characterized by activation of early stages of multiple defense signaling pathways, particularly JA-associated processes. However, the response to Flg22 is stronger in both the number of genes differentially expressed and the amplitude of change. The magnitude of induction of individual genes is in both cases dose-dependent, but, even at very high concentrations, OGs do not induce a response that is as comprehensive as that seen with Flg22. While high doses of either microbe-associated molecular pattern (MAMP) elicit a late response that includes activation of senescence processes, SA-dependent secretory pathway genes and PR1 expression are substantially induced only by Flg22. These results suggest a lower threshold for activation of early responses than for sustained or SA-mediated late defenses. Expression patterns of amino-cyclopropane-carboxylate synthase genes also implicate ethylene biosynthesis in regulation of the late innate immune response.

A calmodulin‐like protein regulates plasmodesmal closure during bacterial immune responses

“…CML41 expression was previously shown to be upregulated by flg22 (Denoux et al ., 2008), so we investigated whether it had a role in pathogen responses. First, we confirmed that CML41 transcription was induced flg22 using quantitative RT‐PCR and expression analysis of the CML41 promoter (Fig.…”

Modification of Plasma Membrane Organization in Tobacco Cells Elicited by Cryptogein

“…For instance, both elicitors induce changes in nuclear and cytosolic Ca 2+ concentrations, yet the changes vary in magnitude and timing (Lecourieux et al, 2005). Whereas cryptogein induces a well-characterized HR in tobacco plants and cell death in suspension cells, flagellin acts as a nonnecrotic elicitor (Denoux et al, 2008). Moreover, cryptogein induces a dramatic depolymerization of cortical microtubules in tobacco cells after 1 h of treatment (Binet et al, 2001), whereas flg22 did not cause any such changes in the radial or cortical microtubules (Guan et al, 2013).…”

“…To confirm the link between triggering of defense signaling and RGM modification, we used flg22, a known activator of plant defense mechanisms (Denoux et al, 2008), especially in tobacco cells (Lecourieux et al, 2002). The timing and intensity of the reactive oxygen species (ROS) productions triggered by flg22 (20 nM) and by cryptogein were comparable (Supplemental Fig.…”

“…If considerable overlap has been found in the responses to different elicitors, suggesting that they activate conserved basal defense responses (Jones and Dangl, 2006), the particular suite of early signaling events, or associated kinetics and intensity, varies depending on the specific elicitor (Garcia-Brugger et al, 2006). Cryptogein and flagellin trigger common signaling events such as ROS production, medium alkalinization, MAP kinase activation, calcium influx, endocytosis, or induction of gene expression GarciaBrugger et al, 2006;Chinchilla et al, 2007;Denoux et al, 2008;Leborgne-Castel et al, 2008), although some discrepancies exist between these two proteinaceous elicitors. For instance, both elicitors induce changes in nuclear and cytosolic Ca 2+ concentrations, yet the changes vary in magnitude and timing (Lecourieux et al, 2005).…”

The Arabidopsis NUCLEUS- AND PHRAGMOPLAST-LOCALIZED KINASE1-Related Protein Kinases Are Required for Elicitor-Induced Oxidative Burst and Immunity

“…Seedlings were examined for the expression of genes that are induced early in response to both OGs and elf18 (Kunze et al, 2004;Denoux et al, 2008). We chose FRK1, a flagellinresponsive receptor-like kinase gene, the expression of which is considered to be strictly regulated by the MAPK cascade (Boudsocq et al, 2010), RET-OX, encoding a protein with homology to reticuline oxidases (Dittrich and Kutchan, 1991), and CYP81F2, encoding a cytochrome P450 involved in indol-3-yl-methyl glucosinolate catabolism (Clay et al, 2009).…”