Doctorate thesis of Montpellier University

Wednesday, November 29, 2019

at 2 PM –Campus de La Gaillarde- Amphi 208 (School Heart)

Impact of root symbiosis on plant adaptation to potassium deficiency: characterization and function of membrane transport systems in the ectomycorrhizal fungus Hebeloma cylindrosporum

BPMP, ELSA team

Doctoral School: GAIA – Biodiversity, Agriculture, Food, Environment, Land, Water
Speciality: BIDAP – Biology, Interactions, Adaptive Plant Diversity
Institution: University of Montpellier

Jury:

Claire VENEAULT-FOURREY, DR-INRA, Univ. de Lorraine, Nancy Rapporteure
Virginie PUECH-PAGÈS, Maître de conf. LRSV, UPS, Castanet-Tolosan, Toulouse Rapporteure
Claude PLASSARD, DR-INRA, Eco&Sols, Montpellier Examinatrice
Joske RUYTINX, Professeure, Vrije Universiteit Brussel, Bruxelles, Belgique Examinatrice
Sabine D. ZIMMERMANN, CR-CNRS, BPMP, Montpellier Directrice de thèse
Bruno TOURAINE, Professeur, Univ. de Montpellier, BPMP, Montpellier Co- Directeur de thèse

Abstract:

A major role of mutualistic interactions between plants and fungi is the improvement of plant nutrition by an exchange of nutrients, due to a better exploration of the soil and a better absorption of water and ions. Therefore, ectomycorrhizal symbiosis, established between woody plants and soil fungi, is crucial for the plant to efficiently take up poorly available nutrients in forest ecosystems. Physiological studies, recent genome sequencing projects and transcriptome analyses have allowed progress towards the identification and characterization of the fungal symbiotic transportome. Potassium (K+) is the most abundant cation in plant cells and is involved in various cellular and physiological processes. Improvement of K+ nutrition by ectomycorrhizal symbiosis has been shown under K+ shortage conditions using the model couple Pinus pinaster and Hebeloma cylindrosporum. Questions are raised to identify the fungal transport systems involved in the uptake of nutrients from the soil and in their transfer towards the plant at the symbiotic fungus-plant interface, called Hartig net. Two types of K+ transporters, Trk and HAK, have been identified as candidates to perform K+ uptake from the soil by extraradical hyphae, and two types of K+ channels, Shaker-like and TOK, that may release K+ by the hyphae of the Hartig net into the plant apoplasm. In my PhD, I focused my research on the three TOK (Two- pore Outward K+) channels of H. cylindrosporum, a channel family specific for fungi. These three TOK channels belong to two different subfamilies, which may imply different roles in potassium nutrition and in symbiosis. One member seems to be especially interesting because of its induction by mycorhization. My PhD aimed to complete the previous results on their functional characterization, expression, localization, and to contribute to the establishment of tools to analyze their physiological roles. In perspective, my results will contribute to a better understanding of the specific roles of these original TOK channel members within the fungus and within the symbiosis.