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PMID:20202172

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Citation

Pracharoenwattana, I, Zhou, W, Keech, O, Francisco, PB, Udomchalothorn, T, Tschoep, H, Stitt, M, Gibon, Y and Smith, SM (2010) Arabidopsis has a cytosolic fumarase required for the massive allocation of photosynthate into fumaric acid and for rapid plant growth on high nitrogen. Plant J. 62:785-95

Abstract

The Arabidopsis genome has two fumarase genes, one of which encodes a protein with mitochondrial targeting information (FUM1) while the other (FUM2) does not. We show that a FUM1-green fluorescent protein fusion is directed to mitochondria while FUM2-red fluorescent protein remains in the cytosol. While mitochondrial FUM1 is an essential gene, cytosolic FUM2 is not required for plant growth. However FUM2 is required for the massive accumulation of carbon into fumarate that occurs in Arabidopsis leaves during the day. In fum2 knock-out mutants, fumarate levels remain low while malate increases, and these changes can be reversed with a FUM2 transgene. The fum2 mutant has lower levels of many amino acids in leaves during the day compared with the wild type, but higher levels at night, consistent with a link between fumarate and amino acid metabolism. To further test this relationship we grew plants in the absence or presence of nitrogen fertilizer. The amount of fumarate in leaves increased several fold in response to nitrogen in wild-type plants, but not in fum2. Malate increased to a small extent in the wild type but to a greater extent in fum2. Growth of fum2 plants was similar to that of the wild type in low nitrogen but much slower in the presence of high nitrogen. Activities of key enzymes of nitrogen assimilation were similar in both genotypes. We conclude that FUM2 is required for the accumulation of fumarate in leaves, which is in turn required for rapid nitrogen assimilation and growth on high nitrogen.

Links

PubMed Online version:10.1111/j.1365-313X.2010.04189.x

Keywords

Arabidopsis/enzymology; Arabidopsis/genetics; Arabidopsis/growth & development; Arabidopsis Proteins/genetics; Arabidopsis Proteins/metabolism; DNA, Bacterial/genetics; Fumarate Hydratase/genetics; Fumarate Hydratase/metabolism; Fumarates/metabolism; Gene Expression Regulation, Plant; Gene Knockout Techniques; Metabolome; Mutagenesis, Insertional; Mutation; Nitrogen/metabolism; Plant Leaves/enzymology; Plant Leaves/genetics; RNA, Plant/genetics

Significance

Annotations

Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status

ARATH:FUM2

located_in

GO:0005829: cytosol

ECO:0000314: direct assay evidence used in manual assertion

C

Seeded From UniProt

complete

ARATH:FUM2

acts_upstream_of_or_within

GO:0006106: fumarate metabolic process

ECO:0000315: mutant phenotype evidence used in manual assertion

P

Seeded From UniProt

complete

ARATH:FUM2

enables

GO:0004333: fumarate hydratase activity

ECO:0000315: mutant phenotype evidence used in manual assertion

F

Seeded From UniProt

complete

ARATH:FUM2

acts_upstream_of_or_within

GO:0042128: nitrate assimilation

ECO:0000315: mutant phenotype evidence used in manual assertion

P

Seeded From UniProt

complete


See also

References

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