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Arabidopsis has a cytosolic fumarase required for the massive allocation of photosynthate into fumaric acid and for rapid plant growth on high nitrogen

journal contribution
posted on 2023-05-18, 11:16 authored by Pracharoenwattana, I, Zhou, W, Keech, O, Francisco, PB, Udomchalothorn, T, Tschoep, H, Stitt, M, Gibon, Y, Steven SmithSteven Smith
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.

History

Publication title

The Plant Journal

Volume

62

Issue

5

Pagination

785-795

ISSN

0960-7412

Department/School

School of Natural Sciences

Publisher

Blackwell Publishing Ltd

Place of publication

9600 Garsington Rd, Oxford, England, Oxon, Ox4 2Dg

Rights statement

© 2010 The Authors. Journal compilation © 2010 Blackwell Publishing Ltd

Repository Status

  • Restricted

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