title: Lateral root stimulation in the early interaction between Arabidopsis thaliana and the ectomycorrhizal fungus Laccaria bicolor: is fungal auxin the trigger?
abstract: Lateral root (LR) stimulation during early signal exchange between plant roots and ectomycorrhizal (ECM) fungi has recently been shown to be achieved by modulation of auxin gradients. We suggested that this modulation could occur through altered polar auxin transport (PAT) and through activation of auxin signalling pathways in the root. However, it remains unclear, which fungal molecules alter auxin pathways inside the plant partner. It has been suggested in previous studies that auxin released by the fungus could trigger observed plant responses during early signal exchange and later on during root colonization. Here we focus on the early interaction and we provide evidence for an alternative mechanism. Indeed, LR stimulation by the fungus in A. thaliana followed a totally different timing than with exogenously applied auxin. Furthermore, experimental conditions that excluded the exchange of soluble molecules while allowing exchange of volatile(s) between the plant and the fungus were sufficient for LR induction, therefore questioning the role of secreted fungal auxin. These data suggest that volatiles released by the fungus and sensed by the plant may act upstream of altered auxin signalling in the plant.
authors.affiliation: INRA and Nancy Université, UMR INRA/Nancy Université 1136 Interactions Arbres/Micro-organismes, IFR 110 Genomique, Ecophysiologie et Ecologie Fonctionnelles, INRA Nancy, Champenoux, France.
authors.forename: Judith
authors.initials: J
authors.lastname: Felten
authors.forename: Valérie
authors.initials: V
authors.lastname: Legué
authors.forename: Franck Anicet
authors.initials: FA
authors.lastname: Ditengou
references.citation: Plant Physiol. 2009 Aug;150(4):2018-29
references.pmid: 19535471
references.citation: Plant Cell. 2009 May;21(5):1495-511
references.pmid: 19435934
references.citation: New Phytol. 1998 Dec;140(4):723-733
references.pmid: 33862952
references.citation: Plant J. 2008 Jul;55(2):335-47
references.pmid: 18435826
references.citation: Tree Physiol. 2002 Dec;22(17):1231-9
references.pmid: 12464576
references.citation: Cell. 2008 Apr 4;133(1):177-91
references.pmid: 18394997
references.citation: Tree Physiol. 2000 Jan;20(2):123-129
references.pmid: 12651480
references.citation: Phytochemistry. 1999 Apr;50(7):1147-52
references.pmid: 10234859
references.citation: Plant Physiol. 2009 Dec;151(4):1991-2005
references.pmid: 19854859