The Transcriptional Innate Immune Response to flg22. Interplay and Overlap with Avr Gene-Dependent Defense Responses and Bacterial Pathogenesis  

Abstract

Animals and plants carry recognition systems to sense bacterial flagellin. Flagellin perception in Arabidopsis involves FLS2, a Leu-rich-repeat receptor kinase. We surveyed the early transcriptional response of Arabidopsis cell cultures and seedlings within 60 min of treatment with flg22, a peptide corresponding to the most conserved domain of flagellin. Using Affymetrix microarrays, approximately 3.0% of 8,200 genes displayed transcript level changes in flg22 elicited suspension cultures and seedlings. FLARE (Flagellin Rapidly Elicited) genes mostly encode signaling components, such as transcription factors, protein kinases/phosphatases, and proteins that regulate protein turnover. Approximately 80% of flg22-induced genes were also upregulated in Arabidopsis seedlings treated with cycloheximide. This suggests that many FLARE genes are negatively regulated by rapidly turned-over repressor proteins. Twenty-one tobacco Avr9/Cf-9 rapidly elicited (ACRE) cDNA full-length sequences were used to search for their Arabidopsis orthologs (AtACRE). We identified either single or multiple putative orthologs for 17 ACRE genes. For 13 of these ACRE genes, at least one Arabidopsis ortholog was induced in flg22-elicited Arabidopsis suspension cells and seedlings. This result revealed a substantial overlap between the Arabidopsis flg22 response and the tobacco Avr9 race-specific defense response. We also compared FLARE gene sets and genes induced in basal or gene-for-gene interactions upon different Pseudomonas syringae treatments, and infer that Pseudomonas syringae pv tomato represses the flagellin-initiated defense response.

Arabidopsis ubiquitin ligase MIEL1 mediates degradation of the transcription factor MYB30 weakening plant defence

“…Interestingly, the intermediate resistance response displayed by miel1/myb30 plants, as compared with myb30 and miel1 plants, suggest the existence of additional defence-related MIEL1 targets that are functionally redundant with MYB30 during the regulation of Arabidopsis defence to pathogens. Although modulation of the expression of several RING genes in plants after treatment with different elicitors has been described [22][23][24][25] , only a few RING proteins have been involved in the regulation of plant immunity and, in most cases, their targets remain unknown. Moreover, the regulation by ubiquitination of the transcriptional activation related to disease resistance is yet poorly documented in plants.…”

Characterization of theVIER F-BOX PROTEINEGenes fromArabidopsisReveals Their Importance for Plant Growth and Development

“…We failed to identify nonplant proteins with a clear homology to the Arabidopsis VFB proteins. However, we identified a putative tobacco (Nicotiana tabacum) VFB homolog designated AVR9/CF-9 RAPIDLY ELICITED PROTEIN 189 (ACRE189), whose expression is induced following flagellin treatment, and two putative rice (Oryza sativa) VFB homologs ACRE189 and JNBb0002J11.1 ( Figure 1C) (Navarro et al, 2004). Since we were unable to assign these proteins unequivocally to a (A) Pretty box representation of a Clustal alignment of the VFB proteins VFB1 (AT1G47056), VFB2 (AT3G50080), VFB3 (AT4G07400), and VFB4 (AT5G67250).…”

Uncoupling of sustained MAMP receptor signaling from early outputs in an Arabidopsis endoplasmic reticulum glucosidase II allele

“…4 A and B). Up-regulation of WRKY22 and WRKY29, encoding members of the WRKY transcription factor family (27), occurs downstream of MAPK activation in response to different MAMPs (2,25,28,29). We thus monitored expression of these genes in WT and rsw3 seedlings during the time course of elf18 treatment.…”