Thesis defended by Muhammad Usman | Institut des Sciences des Plantes de Montpellier

Doctorate thesis of Montpellier University

Friday march 18 at 2pm, Amphi 206

Analysis of molecular mechanisms involved in membrane exchange of nutrients within (ecto)mycorrhizal symbiosis between fungus and plant root for a better adaptation of the host plant to deficiency and salinity stress

Doctorale school : GAIA – Biodiversité, Agriculture, Alimentation, Environnement, Terre, Eau
Spéciality : BIDAP – Biologie, Interactions, Diversité Adaptative des Plantes
Montpellier university

Jury:

Mme. Claire VENEAULT-FOURREY, Directrice de recherche, INRAE, Nancy – Rapporteuse

M. Daniel WIPF, Professeur, Université de Bourgogne, Dijon – Rapporteur

M. Pierre CZERNIC, Professeur, IRD, UMR, IPME, Agropolis, Montpellier – Examinateur

Mme. Joske RUYTINX, Professeure, Vrije Universiteit Brussel, Bruxelles, Belgique – Examinatrice

Mme. Claude PLASSARD, Directrice de recherche, INRAE, Eco&Sols, Montpellier – Examinatrice

Mme. Sabine D. ZIMMERMANN, Chargée de recherche, CNRS, BPMP, Montpellier – Directrice de thèse

Mme. Tania HO-PLAGARO, Postdoc, CNRS, BPMP, Montpellier – Co-encadrante de thèse

Abstract:

Ectomycorrhizal fungi establish beneficial associations with trees especially of temperate and boreal forests. The extraradical mycelia of mycorrhizal fungi explore the soil and provide nutrients to plant roots via soil-fungus-plant interfaces. In return, mycorrhizal plants provide carbon substrates to their root-associated fungi via efficient transport systems. Movement of these nutrients is mediated and regulated by several efficient membrane transport systems present in fungi and plants. Aiming at better knowledge concerning the establishment and functioning of mycorrhizal symbiosis, identification of the underlying molecular mechanisms and characterization of involved membrane transport is needed. Objectives of the PhD project included the analysis of (i) the impact of mycorrhizal symbiosis for plant adaptation to salt stress, (ii) fungal transport systems likely to be involved in mycorrhizal plant potassium nutrition, and (iii) the most mycorrhiza-induced fungal membrane transporter. Model of this study is the ectomycorrhizal association between maritime pine Pinus pinaster and Hebeloma cylindrosporum. Interesting results have been obtained showing that this beneficial association alleviates salt stress tolerance of young pine seedlings. Analyses of the identified fungal potassium transporters was further completed characterizing the second Trk-type transporter as potassium-selective uptake system. Among mycorrhiza-induced membrane transporters, a member of the CDF family was shown to be upregulated at early contact with the host plant and characterized as a zinc transporter. As zinc is an essential micronutrient, needed in sufficient amounts but toxic at high concentrations, fungal and ectomycorrhizal pine growth was analyzed in dependence on external zinc. Summarizing these results, two review articles are included in the PhD and three articles are in preparation for submission.