Proteomic Profiling for Metabolic Pathways Involved in Interactive Effects of Elevated Carbon Dioxide and Nitrogen on Leaf Growth in a Perennial Grass Species

Elevated atmospheric CO2 and nitrogen are major environmental
factors affecting shoot growth. The objectives of this study are to
determine the interactive effects of elevated CO2 and nitrogen
on leaf growth in tall fescue (Festuca arundinacea) and to identify major proteins and associated metabolic pathways
underlying CO2-regulation of leaf growth under insufficient
and sufficient nitrate conditions using proteomic analysis. Plants
of tall fescue treated with low nitrate level (0.25 mM, LN), moderate
nitrate level (4 mM, MN) and high nitrate level (32 mM, HN) were exposed
to ambient (400 μmol mol–1) and elevated (800
μmol mol–1) CO2 concentrations
in environment-controlled growth chambers. Increased atmospheric CO2 concentration increased leaf length and shoot biomass, which
corresponded to increased content of indo-acetic acid, gibberellic
acid, cytokinins and reduced content of abscisic acid under sufficient
nitrate conditions (MN and HN conditions). Low nitrate supply limited
shoot growth and hormonal responses to elevated CO2. Proteomic
analysis of plants exposed to elevated CO2 under LN and
MN conditions demonstrated the increases in the abundance of many
proteins due to elevated CO2 under MN condition involved
with cell cycle and proliferation, transcription and translation,
photosynthesis (ribosomal and chlorophyll a/b-binding proteins), amino
acids synthesis, sucrose and starch metabolism, as well as ABA signaling
pathways (ABA-induced proteins). Our results revealed major proteins
and associated metabolic pathways associated with the interactive
effects of elevated CO2 and nitrate regulating leaf growth
in a perennial grass species.