title: Zn2+ -induced changes at the root level account for the increased tolerance of acclimated tobacco plants.
abstract: Evidence suggests that heavy-metal tolerance can be induced in plants following pre-treatment with non-toxic metal concentrations, but the results are still controversial. In the present study, tobacco plants were exposed to increasing Zn2+ concentrations (up to 250 and/or 500 μM ZnSO4) with or without a 1-week acclimation period with 30 μM ZnSO4. Elevated Zn2+ was highly toxic for plants, and after 3 weeks of treatments there was a marked (≥50%) decline in plant growth in non-acclimated plants. Plant acclimation, on the other hand, increased plant dry mass and leaf area up to 1.6-fold compared with non-acclimated ones. In non-acclimated plants, the addition of 250 μM ZnSO4 led to transient membrane depolarization and stomatal closure within 24h from the addition of the stress; by contrast, the acclimation process was associated with an improved stomatal regulation and a superior ability to maintain a negative root membrane potential, with values on average 37% more negative compared with non-acclimated plants. The different response at the plasma-membrane level between acclimated and non-acclimated plants was associated with an enhanced vacuolar Zn2+ sequestration and up to 2-fold higher expression of the tobacco orthologue of the Arabidopsis thaliana MTP1 gene. Thus, the acclimation process elicited specific detoxification mechanisms in roots that enhanced Zn2+ compartmentalization in vacuoles, thereby improving root membrane functionality and stomatal regulation in leaves following elevated Zn2+ stress.
authors.affiliation: LINV - Department of Agrifood Production and Environmental Sciences - University of Florence, Viale delle Idee 30, 50019 Sesto F.no, Florence, Italy.
authors.forename: Nadia
authors.initials: N
authors.lastname: Bazihizina
authors.affiliation: LINV - Department of Agrifood Production and Environmental Sciences - University of Florence, Viale delle Idee 30, 50019 Sesto F.no, Florence, Italy.
authors.forename: Cosimo
authors.initials: C
authors.lastname: Taiti
authors.affiliation: LINV - Department of Agrifood Production and Environmental Sciences - University of Florence, Viale delle Idee 30, 50019 Sesto F.no, Florence, Italy.
authors.forename: Lucia
authors.initials: L
authors.lastname: Marti
authors.affiliation: LINV - Department of Agrifood Production and Environmental Sciences - University of Florence, Viale delle Idee 30, 50019 Sesto F.no, Florence, Italy.
authors.forename: Ana
authors.initials: A
authors.lastname: Rodrigo-Moreno
authors.affiliation: LINV - Department of Agrifood Production and Environmental Sciences - University of Florence, Viale delle Idee 30, 50019 Sesto F.no, Florence, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Spinelli
authors.affiliation: Centro di Microscopie Elettroniche 'Laura Bonzi' (Ce.M.E.), ICCOM, CNR, Via Madonna del Piano, 50019 Sesto F.no, Florence, Italy.
authors.forename: Cristiana
authors.initials: C
authors.lastname: Giordano
authors.affiliation: LINV - Department of Agrifood Production and Environmental Sciences - University of Florence, Viale delle Idee 30, 50019 Sesto F.no, Florence, Italy.
authors.forename: Stefania
authors.initials: S
authors.lastname: Caparrotta
authors.affiliation: LINV - Department of Agrifood Production and Environmental Sciences - University of Florence, Viale delle Idee 30, 50019 Sesto F.no, Florence, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Gori
authors.affiliation: LINV - Department of Agrifood Production and Environmental Sciences - University of Florence, Viale delle Idee 30, 50019 Sesto F.no, Florence, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Azzarello
authors.affiliation: LINV - Department of Agrifood Production and Environmental Sciences - University of Florence, Viale delle Idee 30, 50019 Sesto F.no, Florence, Italy stefano.mancuso@unifi.it.
authors.forename: Stefano
authors.initials: S
authors.lastname: Mancuso
mesh_terms: D000064:Acclimatization; D002338:Carotenoids / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D018520:Plant Shoots / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D054046:Plant Stomata / Q000187:drug effects / Q000378:metabolism; D014026:Nicotiana / Q000187:drug effects* / Q000378:metabolism*; D015032:Zinc / Q000494:pharmacology*
chemical_list: D002734:Chlorophyll; D002338:Carotenoids; D015032:Zinc
keywords: Acclimation; Nicotiana tabacum; heavy-metal toxicity; membrane potential; stomatal conductance; transporter; vacuole.