title: The microRNA miR393 re-directs secondary metabolite biosynthesis away from camalexin and towards glucosinolates.
abstract: flg22 treatment increases levels of miR393, a microRNA that targets auxin receptors. Over-expression of miR393 renders plants more resistant to biotroph pathogens and more susceptible to necrotroph pathogens. In contrast, over-expression of AFB1, an auxin receptor whose mRNA is partially resistant to miR393 degradation, renders the plant more susceptible to biotroph pathogens. Here we investigate the mechanism by which auxin signalling and miR393 influence plant defence. We show that auxin signalling represses SA levels and signalling. We also show that miR393 represses auxin signalling, preventing it from antagonizing SA signalling. In addition, over-expression of miR393 increases glucosinolate levels and decreases the levels of camalexin. Further studies on pathogen interactions in auxin signalling mutants revealed that ARF1 and ARF9 negatively regulate glucosinolate accumulation, and that ARF9 positively regulates camalexin accumulation. We propose that the action of miR393 on auxin signalling triggers two complementary responses. First, it prevents suppression of SA levels by auxin. Second, it stabilizes ARF1 and ARF9 in inactive complexes. As a result, the plant is able to mount a full SA response and to re-direct metabolic flow toward the most effective anti-microbial compounds for biotroph resistance. We propose that miR393 levels can fine-tune plant defences and prioritize resources.
authors: Sainsbury Laboratory, John Innes Centre, Colney Lane, Norwich, UK.
authors: Alexandre
authors: A
authors: Robert-Seilaniantz
authors: Dan
authors: D
authors: MacLean
authors: Yusuke
authors: Y
authors: Jikumaru
authors: Lionel
authors: L
authors: Hill
authors: Shinjiro
authors: S
authors: Yamaguchi
authors: Yuji
authors: Y
authors: Kamiya
authors: Jonathan D G
authors: JD
authors: Jones
mesh_terms: D000528:Alternaria / Q000472:pathogenicity; D017360:Arabidopsis / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D005961:Glucosinolates / Q000096:biosynthesis*; D007210:Indoleacetic Acids / Q000378:metabolism; D007211:Indoles / Q000378:metabolism*; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D009868:Oomycetes / Q000472:pathogenicity; D057865:Plant Immunity; D044224:Pseudomonas syringae / Q000472:pathogenicity; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism*; D020156:Salicylic Acid / Q000378:metabolism; D015398:Signal Transduction; D013844:Thiazoles / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism; D000094162:Phytoalexins
chemical_list: D029681:Arabidopsis Proteins; D004268:DNA-Binding Proteins; D005961:Glucosinolates; D007210:Indoleacetic Acids; D007211:Indoles; D035683:MicroRNAs; D018749:RNA, Plant; D020156:Salicylic Acid; D013844:Thiazoles; D014157:Transcription Factors; C503841:ARF1 protein, Arabidopsis; C559857:MIRN393 microRNA, Arabidopsis; C102405:camalexin; D000094162:Phytoalexins