myo-Inositol Oxygenase Offers a Possible Entry Point into Plant Ascorbate Biosynthesis

作者：Argelia Lorence, Boris I. Chevone, Pedro Mendes, Craig L. Nessler · 发表于：PLANT PHYSIOLOGY · 年份：2004 · DOI：10.1104/pp.103.033936 · 被引用次数：518 · 研究领域：Plant Stress Responses and Tolerance、Plant responses to water stress、Cassava research and cyanide

Two biosynthetic pathways for ascorbate (l-ascorbic acid [AsA]; vitamin C) in plants are presently known, the mannose/l-galactose pathway and an l-GalUA pathway. Here, we present molecular and biochemical evidence for a possible biosynthetic route using myo-inositol (MI) as the initial substrate. A MI oxygenase (MIOX) gene was identified in chromosome 4 (miox4) of Arabidopsis ecotype Columbia, and its enzymatic activity was confirmed in bacterially expressed recombinant protein. Miox4 was primarily expressed in flowers and leaves of wild-type Arabidopsis plants, tissues with a high concentration of AsA. Ascorbate levels increased 2- to 3-fold in homozygous Arabidopsis lines overexpressing the miox4 open reading frame, thus suggesting the role of MI in AsA biosynthesis and the potential for using this gene for the agronomic and nutritional enhancement of crops.