title: Correlation-Based Network Analysis of Metabolite and Enzyme Profiles Reveals a Role of Citrate Biosynthesis in Modulating N and C Metabolism in Zea mays.
abstract: To investigate the natural variability of leaf metabolism and enzymatic activity in a maize inbred population, statistical and network analyses were employed on metabolite and enzyme profiles. The test of coefficient of variation showed that sugars and amino acids displayed opposite trends in their variance within the population, consistently with their related enzymes. The overall higher CV values for metabolites as compared to the tested enzymes are indicative for their greater phenotypic plasticity. H(2) tests revealed galactinol (1) and asparagine (0.91) as the highest scorers among metabolites and nitrate reductase (0.73), NAD-glutamate dehydrogenase (0.52), and phosphoglucomutase (0.51) among enzymes. The overall low H(2) scores for metabolites and enzymes are suggestive for a great environmental impact or gene-environment interaction. Correlation-based network generation followed by community detection analysis, partitioned the network into three main communities and one dyad, (i) reflecting the different levels of phenotypic plasticity of the two molecular classes as observed for the CV values and (ii) highlighting the concerted changes between classes of chemically related metabolites. Community 1 is composed mainly of enzymes and specialized metabolites, community 2' is enriched in N-containing compounds and phosphorylated-intermediates. The third community contains mainly organic acids and sugars. Cross-community linkages are supported by aspartate, by the photorespiration amino acids glycine and serine, by the metabolically related GABA and putrescine, and by citrate. The latter displayed the strongest node-betweenness value (185.25) of all nodes highlighting its fundamental structural role in the connectivity of the network by linking between different communities and to the also strongly connected enzyme aldolase.
authors.affiliation: Institute of Dryland Biotechnology and Agriculture, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev Midreshet Ben-Gurion, Israel.
authors.forename: David
authors.initials: D
authors.lastname: Toubiana
authors.affiliation: Institute of Dryland Biotechnology and Agriculture, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev Midreshet Ben-Gurion, Israel.
authors.forename: Wentao
authors.initials: W
authors.lastname: Xue
authors.affiliation: Institute for Genomic Diversity, Cornell University Ithaca, NY, USA.
authors.forename: Nengyi
authors.initials: N
authors.lastname: Zhang
authors.affiliation: Institute for Genomic Diversity, Cornell University Ithaca, NY, USA.
authors.forename: Karl
authors.initials: K
authors.lastname: Kremling
authors.affiliation: Institute for Genomic Diversity, Cornell University Ithaca, NY, USA.
authors.forename: Amit
authors.initials: A
authors.lastname: Gur
authors.affiliation: Mitrani Department of Desert Ecology, Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev Midreshet Ben-Gurion, Israel.
authors.forename: Shai
authors.initials: S
authors.lastname: Pilosof
authors.affiliation: Max Planck Institute of Molecular Plant Physiology Golm, Germany.
authors.forename: Yves
authors.initials: Y
authors.lastname: Gibon
authors.affiliation: Max Planck Institute of Molecular Plant Physiology Golm, Germany.
authors.forename: Mark
authors.initials: M
authors.lastname: Stitt
authors.affiliation: Institute for Genomic Diversity, Cornell University Ithaca, NY, USA.
authors.forename: Edward S
authors.initials: ES
authors.lastname: Buckler
authors.affiliation: Max Planck Institute of Molecular Plant Physiology Golm, Germany.
authors.forename: Alisdair R
authors.initials: AR
authors.lastname: Fernie
authors.affiliation: Institute of Dryland Biotechnology and Agriculture, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev Midreshet Ben-Gurion, Israel.
authors.forename: Aaron
authors.initials: A
authors.lastname: Fait
keywords: TCA cycle; Zea mays; correlation-based network analysis; enzymatic processes; metabolic networks and pathways; metabolism