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Tracking the metabolic pulse of plant lipid production with isotopic labeling and flux analyses: Past, present and future

Allen, Doug K., Bates, Philip D., Tjellstorm, Henrik
Progress in lipid research 2015 v.58 pp. 97-120
analytical methods, biochemical pathways, biosynthesis, carbon, fatty acids, instrumentation, isotope labeling, isotopes, lipid metabolism, metabolites, molecular biology, molecular genetics, phenotype, plant physiology, plant tissues
Metabolic networks are comprised of chemical transformations that are the basis of cellular operation and function to sustain life. The molecular rate of transitioning through biochemical pathways (i.e. flux) establishes cellular phenotypes that can be studied in response to genetic or environmental perturbations. Each change evokes a response in metabolic pathway flow and the quantification of fluxes under varied conditions helps to elucidate major and minor routes, and regulatory aspects of metabolism. To measure fluxes requires experimental methods that assess the movements and transformations of metabolites without creating artifacts. Isotopic labeling fills this role and is a long-standing experimental approach to identify pathways and quantify their metabolic relevance in different tissues or under different conditions. The application of labeling techniques to plant science is however far from reaching it potential. In light of advancements in genetics and molecular biology that provide a means to alter metabolism, and given recent improvements in instrumentation, computational tools and available isotopes, the use of isotopic labeling to probe metabolism is becoming more and more powerful. We review the principal analytical methods for isotopic labeling with a focus on seminal studies of pathways and fluxes in lipid metabolism and carbon partitioning through central metabolism. Central carbon metabolic steps are directly linked to lipid production by serving to generate the precursors for fatty acid biosynthesis and lipid assembly. Additionally some of the ideas for labeling techniques that may be most applicable for lipid metabolism in the future have been developed to investigate other aspects of central metabolism. We conclude by describing recent advancements that will play an important future role in quantifying flux and metabolic operation in plant tissues.