title: Paxillus involutus-Facilitated Cd2+Influx through Plasma Membrane Ca2+-Permeable Channels Is Stimulated by H2O2and H+-ATPase in EctomycorrhizalPopulus×canescensunder Cadmium Stress.
abstract: Using a Non-invasive Micro-test Technique, flux profiles of Cd2+, Ca2+, and H+were investigated in axenically grown cultures of two strains ofPaxillus involutus(MAJ and NAU), ectomycorrhizae formed by these fungi with the woody Cd2+-hyperaccumulator,Populus×canescens, and non-mycorrhizal (NM) roots. The influx of Cd2+increased in fungal mycelia, NM and ectomycorrhizal (EM) roots upon a 40-min shock, after short-term (ST, 24 h), or long-term (LT, 7 days) exposure to a hydroponic environment of 50 μM CdCl2. Cd2+treatments (shock, ST, and LT) decreased Ca2+influx in NM and EM roots but led to an enhanced influx of Ca2+in axenically grown EM cultures of the twoP. involutusisolates. The susceptibility of Cd2+flux to typical Ca2+channel blockers (LaCl3, GdCl3, verapamil, and TEA) in fungal mycelia and poplar roots indicated that the Cd2+entry occurred mainly through Ca2+-permeable channels in the plasma membrane (PM). Cd2+treatment resulted in H2O2production. H2O2exposure accelerated the entry of Cd2+and Ca2+in NM and EM roots. Cd2+further stimulated H+pumping activity benefiting NM and EM roots to maintain an acidic environment, which favored the entry of Cd2+across the PM. A scavenger of reactive oxygen species, DMTU, and an inhibitor of PM H+-ATPase, orthovanadate, decreased Ca2+and Cd2+influx in NM and EM roots, suggesting that the entry of Cd2+through Ca2+-permeable channels is stimulated by H2O2and H+pumps. Compared to NM roots, EM roots exhibited higher Cd2+-fluxes under shock, ST, and LT Cd2+treatments. We conclude that ectomycorrhizalP.×canescensroots retained a pronounced H2O2production and a high H+-pumping activity, which activated PM Ca2+channels and thus facilitated a high influx of Cd2+under Cd2+stress.
authors.affiliation: College of Biological Sciences and Technology, Beijing Forestry University Beijing, China.
authors.forename: Yuhong
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: College of Biological Sciences and Technology, Beijing Forestry University Beijing, China.
authors.forename: Gang
authors.initials: G
authors.lastname: Sa
authors.affiliation: College of Biological Sciences and Technology, Beijing Forestry University Beijing, China.
authors.forename: Yinan
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: College of Biological Sciences and Technology, Beijing Forestry University Beijing, China.
authors.forename: Zhimei
authors.initials: Z
authors.lastname: Zhu
authors.affiliation: College of Biological Sciences and Technology, Beijing Forestry University Beijing, China.
authors.forename: Shurong
authors.initials: S
authors.lastname: Deng
authors.affiliation: College of Life Science, Jiangsu Normal University Xuzhou, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Sun
authors.affiliation: College of Biological Sciences and Technology, Beijing Forestry University Beijing, China.
authors.forename: Nianfei
authors.initials: N
authors.lastname: Li
authors.affiliation: School of Computer Science and Technology, Henan Polytechnic University Jiaozuo, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Li
authors.affiliation: College of Biological Sciences and Technology, Beijing Forestry University Beijing, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Yao
authors.affiliation: College of Biological Sciences and Technology, Beijing Forestry University Beijing, China.
authors.forename: Nan
authors.initials: N
authors.lastname: Zhao
authors.affiliation: College of Biological Sciences and Technology, Beijing Forestry University Beijing, China.
authors.forename: Rui
authors.initials: R
authors.lastname: Zhao
authors.affiliation: College of Biological Sciences and Technology, Beijing Forestry University Beijing, China.
authors.forename: Xujun
authors.initials: X
authors.lastname: Ma
authors.affiliation: Büsgen-Institut, Forstbotanik und Baumphysiologie, Georg-August-Universität Göttingen Göttingen, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Polle
authors.affiliation: College of Biological Sciences and Technology, Beijing Forestry University Beijing, China.
authors.forename: Shaoliang
authors.initials: S
authors.lastname: Chen
keywords: Cd2+-hyperaccumulator; MAJ; NAU; NMT; Paxillus involutus; ectomycorrhizal fungi; poplar