Journal Article

Overexpression of Mitochondrial Citrate Synthase in <i>Arabidopsis thaliana</i> Improved Growth on a Phosphorus-Limited Soil

Hiroyuki Koyama, Ayako Kawamura, Tomonori Kihara, Tetsuo Hara, Eiji Takita and Daisuke Shibata

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 41, issue 9, pages 1030-1037
Published in print September 2000 | ISSN: 0032-0781
Published online September 2000 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcd029
Overexpression of Mitochondrial Citrate Synthase in Arabidopsis thaliana Improved Growth on a Phosphorus-Limited Soil

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The gene for mitochondrial citrate synthase (CS) was isolated from Daucus carota (DcCS) and introduced into Arabidopsis thaliana (strain WS) using Agrobacterium tumefaciens-mediated transformation. Characteristics of citrate excretion were compared between T3 transgenic plants, which were derived from the initial transgenic plants by self-fertilization and homozygous for DcCS, and the control plants that had no DcCS. The highest CS activity 0.78 µmol protein min–1 exhibited by the transgenic plants was about threefold greater than that found in the control plants (0.23–0.28 µmol protein min–1). Western analysis of the transgenic plants showed two CS signals corresponding to signals obtained from both D. carota and A. thaliana. Thus, it appears that the CS polypeptides by ectopic expression of DcCS were processed into the mature form and localized in the mitochondria of A. thliana. The signal corresponding to the mature form of DcCS were greater in the transgenic plants having higher levels of CS activity. When the transgenic plants were grown in Al-phosphate media, a correlation between the levels of CS activity and the amounts of citrate excreted into the medium. The highest value (5.1 nmol per plant) was about 2.5-fold greater than that from control plants (1.9 nmol per plant). Both growth and P accumulation were greater in transgenic plants with high CS activity than that in control plants when they were grown on an acid soil where the availability of phosphate was low due to the formation of Al-phosphate. It appears that the overexpression of CS in A. thaliana improves the growth in phosphorous limited soil as a result of enhanced citrate excretion from the roots.

Keywords: Key words: Al-phosphate — Arabidopsis thaliana — Citrate synthase (EC 4.1.3.7) — Daucus carota — Transformation.; Abbreviations: AtCS, A. thaliana mitochondrial CS; CS, citrate synthase; DcCS, carrot mitochondrial CS; GUS, β-glucuronidase; Hyg, hygromycin; Km, kanamycin; WT, wild-type.

Journal Article.  6084 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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