title: Differential capacity for high-affinity manganese uptake contributes to differences between barley genotypes in tolerance to low manganese availability.
abstract: There is considerable variability among barley (Hordeum vulgare) genotypes in their ability to grow in soils containing a low level of plant available manganese (Mn). The physiological basis for the tolerance to low Mn availability is unknown. In this work, Mn2+ influx and compartmentation in roots of the Mn-efficient genotype Vanessa and the Mn-inefficient genotype Antonia were investigated. Two separate Mn transport systems, mediating high-affinity Mn2+ influx at concentrations up to 130 nm and low-affinity Mn2+ influx at higher concentrations, were identified in both genotypes. The two genotypes differed only in high-affinity kinetics with the Mn-efficient genotype Vanessa having almost 4 times higher V(max) than the inefficient Antonia, but similar K(m) values. Online inductively coupled plasma-mass spectrometry measurements verified that the observed differences in high-affinity influx resulted in a higher Mn net uptake of Vanessa compared to Antonia. Further evidence for the importance of the differences in high-affinity uptake kinetics for Mn acquisition was obtained in a hydroponic system with mixed cultivation of the two genotypes at a continuously low Mn concentration (10-50 nm) similar to that occurring in soil solution. Under these conditions, Vanessa had a competitive advantage and contained 55% to 75% more Mn in the shoots than did Antonia. Subcellular compartmentation analysis of roots based on 54Mn2+ efflux established that up to 93% and 83% of all Mn was present in the vacuole in Vanessa and Antonia, respectively. It is concluded that differential capacity for high-affinity Mn influx contributes to differences between barley genotypes in Mn efficiency.
authors.affiliation: Plant and Soil Science Laboratory, Department of Agricultural Sciences , Royal Veterinary and Agricultural University, DK-1871 Frederiksberg C, Copenhagen, Denmark.
authors.forename: Pai
authors.initials: P
authors.lastname: Pedas
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Hebbern
authors.forename: Jan K
authors.initials: JK
authors.lastname: Schjoerring
authors.forename: Peter E
authors.initials: PE
authors.lastname: Holm
authors.forename: Søren
authors.initials: S
authors.lastname: Husted
mesh_terms: D001692:Biological Transport; D002473:Cell Wall / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D005838:Genotype; D006207:Half-Life; D001467:Hordeum / Q000166:cytology / Q000187:drug effects / Q000235:genetics* / Q000502:physiology*; D007700:Kinetics; D008345:Manganese / Q000378:metabolism* / Q000494:pharmacology; D013058:Mass Spectrometry; D018517:Plant Roots / Q000378:metabolism; D018520:Plant Shoots; D014617:Vacuoles / Q000378:metabolism
chemical_list: D008345:Manganese