Pseudomonas fluorescens C7R12 type III secretion system impacts mycorrhization of Medicago truncatula and associated microbial communities

Type three secretion systems (T3SSs) mediate cell-to-cell interactions between Gram-negative bacteria and eukaryotes. We hypothesized that fluorescent pseudomonads harboring T3SS (T3SS+) would be beneficial to arbuscular mycorrhizal symbiosis because non-pathogenic fluorescent pseudomonads have been...

Full description

Saved in:

Bibliographic Details
Published in:	Mycorrhiza 2017, Vol.27 (1), p.23-33
Main Authors:	Viollet, Amandine, Pivato, Barbara, Mougel, Christophe, Cleyet-Marel, Jean-Claude, Gubry-Rangin, Cécile, Lemanceau, Philippe, Mazurier, Sylvie
Format:	Article
Language:	eng
Subjects:	Agriculture Biodiversity and Ecology Biomedical and Life Sciences Ecology Environmental Sciences Forestry Fungi - classification Fungi - genetics Gene Expression Regulation, Bacterial - physiology Life Sciences Medicago truncatula Medicago truncatula - microbiology Microbiology Mutation Mycorrhizae - physiology Original Article Plant Roots - microbiology Plant Sciences Pseudomonas fluorescens Pseudomonas fluorescens - classification Pseudomonas fluorescens - genetics Pseudomonas fluorescens - physiology Soil Microbiology Type III Secretion Systems - physiology
Online Access:	Get full text
Tags:	Add Tag No Tags, Be the first to tag this record!

Description
Summary:	Type three secretion systems (T3SSs) mediate cell-to-cell interactions between Gram-negative bacteria and eukaryotes. We hypothesized that fluorescent pseudomonads harboring T3SS (T3SS+) would be beneficial to arbuscular mycorrhizal symbiosis because non-pathogenic fluorescent pseudomonads have been previously shown to be much more abundant in mycorrhizal than in non-mycorrhizal roots. We tested this hypothesis by comparing mycorrhization and the associated rhizosphere microbial communities of Medicago truncatula grown in a non-sterile soil inoculated with either the T3SS+ mycorrhiza helper bacterium Pseudomonas fluorescens (C7R12) or a T3SS− mutant of the strain. Results showed that the bacterial secretion system was responsible for the promotion of mycorrhization because root colonization by arbuscular mycorrhizal fungi was not promoted by the T3SS− mutant. The observed T3SS-mediated promotion of mycorrhization was associated with changes in the rhizosphere bacterial communities and the increased occurrence of Claroidoglomeraceae within the intraradical arbuscular mycorrhizal fungi. Furthermore, both pseudomonad strains promoted the host-free growth of a model arbuscular mycorrhizal fungus in vitro, suggesting that T3SS-mediated promotion of mycorrhization occurs during plant-fungal interactions rather than during the pre-symbiotic phase of fungal growth. Taken together, these data provide evidence for the involvement of T3SS in promoting arbuscular mycorrhization by a model fluorescent pseudomonad and suggest the implication of interactions between the bacterium and mycorrhizas.
ISSN:	0940-6360 1432-1890