Ascorbate oxidase: The unexpected involvement of a ‘wasteful enzyme’\ud in the symbioses with nitrogen-fixing bacteria and arbuscular mycorrhizal fungi

摘要

Ascorbate oxidase (AO, EC 1.10.3.3) catalyzes the oxidation of ascorbate (AsA) to yield water. AO overexpressing\udplants are prone to ozone and salt stresses, whereas lower expression apparently confers\udresistance to unfavorable environmental conditions. Previous studies have suggested a role for AO as\uda regulator of oxygen content in photosynthetic tissues. For the first time we show here that the\udexpression of a Lotus japonicus AO gene is induced in the symbiotic interaction with both nitrogen-fixing\udbacteria and arbuscular mycorrhizal (AM) fungi. In this framework, high AO expression is viewed as\uda possible strategy to down-regulate oxygen diffusion in root nodules, and a component of AM symbiosis.\udA general model of AO function in plants is discussed.