title: Depletion of carbohydrate reserves limits nitrate uptake during early regrowth in Lolium perenne L.
abstract: The mechanisms linking C/N balance to N uptake and assimilation are central to plant responses to changing soil nutrient levels. Defoliation and subsequent regrowth of grasses both impact C partitioning, thereby creating a significant point of interaction with soil N availability. Using defoliation as an experimental treatment, we investigated the dynamic relationships between plant carbohydrate status and NO3--responsive uptake systems, transporter gene expression, and nitrate assimilation in Lolium perenne L. High- and low-affinity NO3- uptake was reduced in an N-dependent manner in response to a rapid and large shift in carbohydrate remobilization triggered by defoliation. This reduction in NO3- uptake was rescued by an exogenous glucose supplement, confirming the carbohydrate dependence of NO3- uptake. The regulation of NO3- uptake in response to the perturbation of the plant C/N ratio was associated with changes in expression of putative high- and low-affinity NO3- transporters. Furthermore, NO3- assimilation appears to be regulated by the C-N status of the plant, implying a mechanism that signals the availability of C metabolites for NO3- uptake and assimilation at the whole-plant level. We also show that cytokinins may be involved in the regulation of N acquisition and assimilation in response to the changing plant C/N ratio.
authors.affiliation: School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand.
authors.forename: Qianqian
authors.initials: Q
authors.lastname: Guo
authors.affiliation: School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand.
authors.forename: Matthew Hamish
authors.initials: MH
authors.lastname: Turnbull
authors.affiliation: School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand.|School of Life Sciences, Yantai University, Yantai 264005, China.
authors.forename: Jiancheng
authors.initials: J
authors.lastname: Song
authors.affiliation: School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand.
authors.forename: Jessica
authors.initials: J
authors.lastname: Roche
authors.affiliation: Laboratory of Growth Regulators, Centre of the Region Haná for Biotechnological and Agricultural Research, Institute of Experimental Botany CAS & Faculty of Science of Palacký University, Šlechtitelu 27, 783 71 Olomouc, Czech Republic.
authors.forename: Ondrej
authors.initials: O
authors.lastname: Novak
authors.affiliation: Swedish Metabolomics Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences KBC, Umeå University, Linnéus väg 6, SE-90183 Umeå, Sweden.
authors.forename: Jana
authors.initials: J
authors.lastname: Späth
authors.affiliation: School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand.
authors.forename: Paula Elizabeth
authors.initials: PE
authors.lastname: Jameson
authors.affiliation: School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Love
mesh_terms: D050260:Carbohydrate Metabolism; D018506:Gene Expression Regulation, Plant; D008129:Lolium / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D009566:Nitrates / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D009566:Nitrates; D010940:Plant Proteins; D009584:Nitrogen
keywords: Carbohydrate; Lolium perenne; carbon; cytokinin; fructan; nitrate transporter (NRT); nitrate uptake; nitrogen; nitrogen use efficiency (NUE); perennial ryegrass.