Journal Article

UDP-Glucose Pyrophosphorylase is Rate Limiting in Vegetative and Reproductive Phases in <i>Arabidopsis thaliana</i>

Jong-In Park, Takeshi Ishimizu, Keita Suwabe, Keisuke Sudo, Hiromi Masuko, Hirokazu Hakozaki, Ill-Sup Nou, Go Suzuki and Masao Watanabe

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 51, issue 6, pages 981-996
Published in print June 2010 | ISSN: 0032-0781
Published online April 2010 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcq057
UDP-Glucose Pyrophosphorylase is Rate Limiting in Vegetative and Reproductive Phases in Arabidopsis thaliana

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  • Biochemistry
  • Molecular and Cell Biology
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UDP-glucose pyrophosphorylase (UGPase) is an important enzyme in the metabolism of UDP-glucose, a precursor for the synthesis of carbohydrate cell wall components, such as cellulose and callose. The Arabidopsis thaliana genome contains two putative genes encoding UGPase, AtUGP1 and AtUGP2. These genes are expressed in all organs. In order to determine the role of UGPase in vegetative and reproductive organs, we employed a reverse genetic approach using the T-DNA insertion mutants, atugp1 and atugp2. Despite a significant decrease in UGPase activity in both the atugp1 and atugp2 single mutants, no decrease in normal growth and reproduction was observed. In contrast, the atugp1/atugp2 double mutant displayed drastic growth defects and male sterility. At the reproductive phase, in the anthers of atugp1/atugp2, pollen mother cells developed normally, but callose deposition around microspores was absent. Genes coding for enzymes at the subsequent steps in the cellulose and callose synthesis pathway were also down-regulated in the double mutant. Taken together, these results demonstrate that the AtUGP1 and AtUGP2 genes are functionally redundant and UGPase activity is essential for both vegetative and reproductive phases in Arabidopsis. Importantly, male fertility was not restored in the double knockout mutant by an application of external sucrose, whereas vegetative growth was comparable in size with that of the wild type. In contrast, an application of external UDP-glucose recovered male fertility in the double mutant, suggesting that control of UGPase in carbohydrate metabolism is different in the vegetative phase as compared with the reproductive phase in A. thaliana.

Keywords: Arabidopsis thaliana; Callose synthesis; Carbohydrate metabolism; Male sterility; UDP-glucose; UGPase

Journal Article.  7625 words.  Illustrated.

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

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