Download or read book Activation of Arabidopsis Thalianad Defense Response Pathways by Oligogalacturonides and Flagellin written by Carine Denoux and published by . This book was released on 2009 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt: Pathogen attacks are perceived in Arabidopsis thaliana through recognition of pathogen- or microbe- associated molecular patterns (PAMPs/MAMPs). Although the study of various elicitors has revealed significant overlaps in defense response, the degrees of similarity/difference between MAMPs are not well defined. Oligogalacturonides (OGs), plant cell wall-derived elicitors, induce a wide range of defenses responses. Transcript profiling of Arabidopsis seedlings treated with OGs indicates that the response to OGs involves a transient response in the regulation of many genes. Among the genes, two cytochrome P450s, CYP81F2 and CYP82C3, are significantly induced shortly after OGs treatment. Monitoring the expression of these genes in a variety of defense-related mutants suggests that their rapid induction, mediated by OGs is independent of SA, JA, or Et signaling pathways. These reporter genes are also highly expressed in response to other MAMPs, including lipopolysaccharide (LPS), flagellin (Flg22), or chitin. Additional transcriptional analysis was carried out with OGs and pathogensynthesized flagellin (Flg22), two very different elicitors. Both triggered a fast and transient response that are similar. This response is characterized by activation of the early stages of multiple defense signaling pathways, particularly JA-associated processes. However, the response to Flg22 is stronger in the number of genes differentially expressed and the amplitude of change. The magnitude of genes induction was in both cases dose-dependent, but, even at very high concentrations, OGs did not induce as many genes as Flg22. Moreover, activation of senescence processes, SA-dependent secretory pathway genes, and PR1 expression was only observed with Flg22 elicitation. These results suggest a lower threshold for activation of early responses than for sustained late innate immune defenses. Induction of the Arabidopsis CYP81F2 gene is part of the early induced response to elicitors (OGs and Flg22). CYP81F2 gene expression is independent of the SA-, JAand Et-signaling pathways. CYP81F2 seems to catalyze the 4 methoxylation of indolic glucosinolates, which is required for callose formation in response to Flg22.