Abstract
Natural genetic diversity provides a powerful resource to investigate how networks respond to multiple simultaneous changes. In this work, we profile maximum catalytic activities of 37 enzymes from central metabolism and generate a matrix to investigate species-wide connectivity between metabolites, enzymes, and biomass. Most enzyme activities change in a highly coordinated manner, especially those in the Calvin-Benson cycle. Metabolites show coordinated changes in defined sectors of metabolism. Little connectivity was observed between maximum enzyme activities and metabolites, even after applying multivariate analysis methods. Measurements of posttranscriptional regulation will be required to relate these two functional levels. Individual enzyme activities correlate only weakly with biomass. However, when they are used to estimate protein abundances, and the latter are summed and expressed as a fraction of total protein, a significant positive correlation to biomass is observed. The correlation is additive to that obtained between starch and biomass. Thus, biomass is predicted by two independent integrative metabolic biomarkers: preferential investment in photosynthetic machinery and optimization of carbon use.
Highlights
The rate of plant growth depends on the rate of photosynthetic carbon (C) assimilation and on developmental programs that influence how efficiently C is converted into biomass
They were grown in short-day conditions at 208C to focus on the response during vegetative growth with limiting C and excess N and harvested at the end of the light period when internal resources like starch and amino acids have accumulated to their diurnal maxima
This allows assays to be performed at very high extract dilutions, which minimizes interference by other components of the extract
Summary
The rate of plant growth depends on the rate of photosynthetic carbon (C) assimilation and on developmental programs that influence how efficiently C is converted into biomass. These processes are sometimes termed source and sink strength, respectively. Reverse genetics has been widely used to study the relationship between the expression individual enzymes and the rate of photosynthesis (Stitt et al, 2010b). Inhibition of photosynthesis due to decreased expression of Rubisco leads to a strong inhibition of growth in nitrogenreplete conditions but not in nitrogen-limited conditions (Stitt and Schulze, 1994). Free air CO2 elevation studies reveal that higher rates of photosynthesis rarely lead to a commensurate increase in biomass (Long et al, 2006; Rogers and Ainsworth, 2006; Leakey et al, 2009)
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