Premium
The metabolic flux phenotype of heterotrophic Arabidopsis cells reveals a flexible balance between the cytosolic and plastidic contributions to carbohydrate oxidation in response to phosphate limitation
Author(s) -
Masakapalli Shyam K.,
Bryant Fiona M.,
Kruger Nicholas J.,
Ratcliffe R. George
Publication year - 2014
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.12522
Subject(s) - flux (metallurgy) , biochemistry , phosphoenolpyruvate carboxylase , plastid , phosphoenolpyruvate carboxykinase , phosphate , flux balance analysis , metabolic pathway , malic enzyme , biology , arabidopsis , carbohydrate , metabolism , arabidopsis thaliana , cytosol , enzyme , chemistry , chloroplast , gene , mutant , organic chemistry , dehydrogenase
Summary Understanding the mechanisms that allow plants to respond to variable and reduced availability of inorganic phosphate is of increasing agricultural importance because of the continuing depletion of the rock phosphate reserves that are used to combat inadequate phosphate levels in the soil. Changes in gene expression, protein levels, enzyme activities and metabolite levels all point to a reconfiguration of the central metabolic network in response to reduced availability of inorganic phosphate, but the metabolic significance of these changes can only be assessed in terms of the fluxes supported by the network. Steady‐state metabolic flux analysis was used to define the metabolic phenotype of a heterotrophic Arabidopsis thaliana cell culture grown on a Murashige and Skoog medium containing 0, 1.25 or 5 m m inorganic phosphate. Fluxes through the central metabolic network were deduced from the redistribution of 13 C into metabolic intermediates and end products when cells were labelled with [1‐ 13 C], [2‐ 13 C], or [ 13 C 6 ]glucose, in combination with 14 C measurements of the rates of biomass accumulation. Analysis of the flux maps showed that reduced levels of phosphate in the growth medium stimulated flux through phosphoenolpyruvate carboxylase and malic enzyme, altered the balance between cytosolic and plastidic carbohydrate oxidation in favour of the plastid, and increased cell maintenance costs. We argue that plant cells respond to phosphate deprivation by reconfiguring the flux distribution through the pathways of carbohydrate oxidation to take advantage of better phosphate homeostasis in the plastid.