Balancing myo‐inositol use in metabolic and signaling pathways

• Published in: The FASEB journal 2007-04, Vol.21 (5), p.A256-A256
• Main Authors: Alford, Shannon Recca, Gillaspy, Glenda E.
• Format: Article
• Language: English
• ISSN: 0892-6638; 1530-6860
• DOI: 10.1096/fasebj.21.5.A256-c

Myo‐inositol (Ins) is used as a backbone of inositol phosphate (InsP) and phosphatidylinositol phosphate signaling molecules, and is also a precursor for an alternative Vitamin C synthesis pathway. Oxidation of Ins by the enzyme myo‐inositol oxygenase (MIOX) produces D‐glucuronic acid, which is further altered to produce Vitamin C. The Arabidopsis genome contains four genes predicted to encode MIOX enzymes. It was shown that plants ectopically expressing the MIOX4 gene from Arabidopsis (MIOX4+) produced higher levels of Vitamin C. We are interested in whether the ectopic expression of the MIOX4 gene results in Ins signaling alterations, an important consideration for future Vitamin C genetic engineering efforts. To test this, we measured Ins and related metabolites by GC analysis of MIOX4+ tissues from several developmental stages. We found a significant decrease in Ins and Ins(1,4,5)P3 in seedlings. The decrease in Ins and Ins(1,4,5)P3 was accompanied by insensitivity to ABA, a plant drought hormone that uses Ins(1,4,5)P3 as a second messenger. This result suggests that MIOX4+ plants are compromised in their ability to synthesize Ins(1,4,5)P3 in response to ABA, and indicates that MIOX overexpression impacts Ins signaling as well as metabolism. NSF Award # MCB 0316705