The fungal transporter Trk2 from Hebeloma cylindrosporum mediates potassium uptake and is expressed in maritime pine ectomycorrhizae
Abstract
Low potassium (K + ) availability in soil is a limiting factor for growth and cellular functions in plants. Ectomycorrhizal (EcM) fungi are important symbiotic partners in temperate and boreal forests for enhancing tree mineral nutrition including K + uptake. Among the membrane transport systems of the EcM fungus Hebeloma cylindrosporum, two members from the Trk (Transporter of K + ) family have been identified and named HcTrk1 and HcTrk2. Although HcTrk1 has been characterized as K + importer and shown to mediate even more sodium (Na + ) influx, the functional properties of HcTrk2 have not been revealed yet. Here, we studied the properties of HcTrk2, aiming at understanding the transporter's localization, function and potential specificity or complementarity of these two Trk members. In situ hybridization within ectomycorrhizae formed between H. cylindrosporum and roots of young maritime pine (Pinus pinaster) seedlings, showed an expression of HcTrk2 in EcM structures including the extraradical mycelium. The efficient K + uptake ability of HcTrk2 was confirmed by yeast (Saccharomyces cerevisiae) mutant complementation assays. Electrophysiological characterization by heterologous expression in Xenopus laevis oocytes revealed higher inward currents for K + than for all other cations tested including Na + , indicating a higher K + transport capacity of HcTrk2 than found for HcTrk1. HcTrk2 is suggested to play a distinct role in fungal K + uptake and thus to contribute to crucial mycorrhizal plant K + nutrition in nutrient poor soils.
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BibTeX
@misc{usman2026fungal,
title = {{The fungal transporter Trk2 from Hebeloma cylindrosporum mediates potassium uptake and is expressed in maritime pine ectomycorrhizae}},
author = {Muhammad Usman and Tania Ho-Plágaro and Amandine Delteil and Sylvain Kumanski and Claire Corratgé-Faillie and Elsa Demes and Alexis de Angeli and Isabelle Gaillard and Kevin Garcia and Sabine Zimmermann},
howpublished = {HAL},
year = {2026},
month = sep,
doi = {10.2139/ssrn.7404611},
url = {https://hal.inrae.fr/hal-05741245v1},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - The fungal transporter Trk2 from Hebeloma cylindrosporum mediates potassium uptake and is expressed in maritime pine ectomycorrhizae
AU - Muhammad Usman
AU - Tania Ho-Plágaro
AU - Amandine Delteil
AU - Sylvain Kumanski
AU - Claire Corratgé-Faillie
AU - Elsa Demes
AU - Alexis de Angeli
AU - Isabelle Gaillard
AU - Kevin Garcia
AU - Sabine Zimmermann
PY - 2026
DA - 2026/09/07
PB - HAL
DO - 10.2139/ssrn.7404611
UR - https://hal.inrae.fr/hal-05741245v1
AB - Low potassium (K + ) availability in soil is a limiting factor for growth and cellular functions in plants. Ectomycorrhizal (EcM) fungi are important symbiotic partners in temperate and boreal forests for enhancing tree mineral nutrition including K + uptake. Among the membrane transport systems of the EcM fungus Hebeloma cylindrosporum, two members from the Trk (Transporter of K + ) family have been identified and named HcTrk1 and HcTrk2. Although HcTrk1 has been characterized as K + importer and shown to mediate even more sodium (Na + ) influx, the functional properties of HcTrk2 have not been revealed yet. Here, we studied the properties of HcTrk2, aiming at understanding the transporter's localization, function and potential specificity or complementarity of these two Trk members. In situ hybridization within ectomycorrhizae formed between H. cylindrosporum and roots of young maritime pine (Pinus pinaster) seedlings, showed an expression of HcTrk2 in EcM structures including the extraradical mycelium. The efficient K + uptake ability of HcTrk2 was confirmed by yeast (Saccharomyces cerevisiae) mutant complementation assays. Electrophysiological characterization by heterologous expression in Xenopus laevis oocytes revealed higher inward currents for K + than for all other cations tested including Na + , indicating a higher K + transport capacity of HcTrk2 than found for HcTrk1. HcTrk2 is suggested to play a distinct role in fungal K + uptake and thus to contribute to crucial mycorrhizal plant K + nutrition in nutrient poor soils.
SN - 2452-2198
ER -