title: β-Glucosidase BGLU42 is a MYB72-dependent key regulator of rhizobacteria-induced systemic resistance and modulates iron deficiency responses in Arabidopsis roots.
abstract: Selected soil-borne rhizobacteria can trigger an induced systemic resistance (ISR) that is effective against a broad spectrum of pathogens. In Arabidopsis thaliana, the root-specific transcription factor MYB72 is required for the onset of ISR, but is also associated with plant survival under conditions of iron deficiency. Here, we investigated the role of MYB72 in both processes. To identify MYB72 target genes, we analyzed the root transcriptomes of wild-type Col-0, mutant myb72 and complemented 35S:FLAG-MYB72/myb72 plants in response to ISR-inducing Pseudomonas fluorescens WCS417. Five WCS417-inducible genes were misregulated in myb72 and complemented in 35S:FLAG-MYB72/myb72. Amongst these, we uncovered β-glucosidase BGLU42 as a novel component of the ISR signaling pathway. Overexpression of BGLU42 resulted in constitutive disease resistance, whereas the bglu42 mutant was defective in ISR. Furthermore, we found 195 genes to be constitutively upregulated in MYB72-overexpressing roots in the absence of WCS417. Many of these encode enzymes involved in the production of iron-mobilizing phenolic metabolites under conditions of iron deficiency. We provide evidence that BGLU42 is required for their release into the rhizosphere. Together, this work highlights a thus far unidentified link between the ability of beneficial rhizobacteria to stimulate systemic immunity and mechanisms induced by iron deficiency in host plants.
authors.affiliation: Plant-Microbe Interactions, Department of Biology, Faculty of Science, Utrecht University, PO Box 800.56, 3508 TB, Utrecht, the Netherlands.
authors.forename: Christos
authors.initials: C
authors.lastname: Zamioudis
authors.forename: Johannes
authors.initials: J
authors.lastname: Hanson
authors.forename: Corné M J
authors.initials: CM
authors.lastname: Pieterse
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000201:enzymology* / Q000235:genetics / Q000276:immunology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D017930:Genes, Reporter; D054884:Host-Pathogen Interactions; D062385:Hydroxybenzoates / Q000378:metabolism; D000090463:Iron Deficiencies; D009154:Mutation; D010935:Plant Diseases / Q000276:immunology* / Q000382:microbiology; D057865:Plant Immunity; D018515:Plant Leaves / Q000166:cytology / Q000201:enzymology / Q000235:genetics / Q000276:immunology; D018517:Plant Roots / Q000166:cytology / Q000201:enzymology / Q000235:genetics / Q000276:immunology; D011551:Pseudomonas fluorescens / Q000502:physiology; D012231:Rhizobium / Q000502:physiology; D058441:Rhizosphere; D036226:Seedlings / Q000166:cytology / Q000201:enzymology / Q000235:genetics / Q000276:immunology; D015398:Signal Transduction; D013312:Stress, Physiological; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D001617:beta-Glucosidase / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D062385:Hydroxybenzoates; C530164:Myb72 protein, Arabidopsis; D014157:Transcription Factors; C000598332:BGLU42 protein, Arabidopsis; D001617:beta-Glucosidase; C017616:phenolic acid
keywords: MYB transcription factors; Pseudomonas fluorescens; beneficial microbes; glucoside hydrolase; induced systemic resistance (ISR); iron deficiency response; rhizosphere