Analysis of metabolic flux phenotypes for two Arabidopsis mutants with severe impairment in seed storage lipid synthesis

Journal Article · Sun Nov 01 04:00:00 EST 2009 · Plant Physiology

DOI:https://doi.org/10.1104/pp.109.144121· OSTI ID:1040337

Lonien, J; Schwender, J

Major storage reserves of Arabidopsis (Arabidopsis thaliana) seeds are triacylglycerols (seed oils) and proteins. Seed oil content is severely reduced for the regulatory mutant wrinkled1 (wri1-1; At3g54320) and for a double mutant in two isoforms of plastidic pyruvate kinase (pkp{beta}{sub 1}pkp{alpha}; At5g52920 and At3g22960). Both already biochemically well-characterized mutants were now studied by {sup 13}C metabolic flux analysis of cultured developing embryos based on comparison with their respective genetic wild-type backgrounds. For both mutations, in seeds as well as in cultured embryos, the oil fraction was strongly reduced while the fractions of proteins and free metabolites increased. Flux analysis in cultured embryos revealed changes in nutrient uptakes and fluxes into biomass as well as an increase in tricarboxylic acid cycle activity for both mutations. While in both wild types plastidic pyruvate kinase (PK{sub p}) provides most of the pyruvate for plastidic fatty acid synthesis, the flux through PK{sub p} is reduced in pkp{beta}{sub 1}pkp{alpha} by 43% of the wild-type value. In wri1-1, PK{sub p} flux is even more reduced (by 82%), although the genes PKp{beta}{sub 1} and PKp{alpha} are still expressed. Along a common paradigm of metabolic control theory, it is hypothesized that a large reduction in PK{sub p} enzyme activity in pkp{beta}{sub 1}pkp{alpha} has less effect on PK{sub p} flux than multiple smaller reductions in glycolytic enzymes in wri1-1. In addition, only in the wri1-1 mutant is the large reduction in PK{sub p} flux compensated in part by an increased import of cytosolic pyruvate and by plastidic malic enzyme. No such limited compensatory bypass could be observed in pkp{beta}{sub 1}pkp{alpha}.

• Research Organization: BROOKHAVEN NATIONAL LABORATORY (BNL)
• Sponsoring Organization: USDOE SC OFFICE OF SCIENCE (SC)
• DOE Contract Number: AC02-98CH10886
• OSTI ID: 1040337
• Report Number(s): BNL--90594-2010-JA; KC0304000
• Journal Information: Plant Physiology, Journal Name: Plant Physiology Journal Issue: 3 Vol. 151; ISSN 0032-0889
• Country of Publication: United States
• Language: English

Related Subjects

09 BIOMASS FUELS
59 BASIC BIOLOGICAL SCIENCES
ARABIDOPSIS
BIOMASS
CARBOXYLIC ACIDS
CONTROL THEORY
EMBRYOS
ENZYME ACTIVITY
ENZYMES
GENES
GENETICS
IMPORTS
LIPIDS
METABOLITES
MUTANTS
MUTATIONS
Metabolic flux analysis
NUTRIENTS
PHOSPHOTRANSFERASES
PROTEINS
SEEDS
STORAGE
SYNTHESIS
carbon partitioning
fatty acids
seed maturation
storage lipid synthesis