PIPRA, Department of Plant Sciences, University of California, Davis, CA 95616, USA.
Plant Physiol Biochem. 2011 Oct;49(10):1244-9. doi: 10.1016/j.plaphy.2011.08.003. Epub 2011 Aug 17.
Vitamin C (L-ascorbate, AsA) is an essential nutrient required in key metabolic functions in humans and must be obtained from the diet, mainly from fruits and vegetables. Given its importance in human health and plant physiology we sought to examine the role of the ascorbate recycling enzymes monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR) in tomato (Solanum lycopersicum), an economically important fruit crop. Cytosolic-targeted tomato genes Mdhar and Dhar were cloned and over-expressed under a constitutive promoter in tomato var. Micro-Tom. Lines with increased protein levels and enzymatic activity were identified and examined. Mature green and red ripe fruit from DHAR over-expressing lines had a 1.6 fold increase in AsA content in plants grown under relatively low light conditions (150 μmol m(-2) s(-1)). Conversely, MDHAR over-expressers had significantly reduced AsA levels in mature green fruits by 0.7 fold. Neither over-expressing line had altered levels of AsA in foliar tissues. These results underscore a complex regulation of the AsA pool size in tomato.
维生素 C（L-抗坏血酸，AsA）是人类关键代谢功能所必需的营养物质，必须从饮食中获得，主要来自水果和蔬菜。鉴于其在人类健康和植物生理学中的重要性，我们试图研究抗坏血酸循环酶单脱氢抗坏血酸还原酶（MDHAR）和脱氢抗坏血酸还原酶（DHAR）在经济上重要的水果作物番茄（Solanum lycopersicum）中的作用。我们克隆了质体靶向番茄基因 Mdhar 和 Dhar，并在番茄品种 Micro-Tom 的组成型启动子下进行了过表达。鉴定并检查了蛋白水平和酶活性增加的株系。在相对低光照条件（150 μmol m(-2) s(-1)）下生长的 DHAR 过表达系的成熟绿色和红色成熟果实中的 AsA 含量增加了 1.6 倍。相反，MDHAR 过表达植株的成熟绿色果实中的 AsA 水平降低了 0.7 倍。这两种过表达系在叶片组织中的 AsA 水平均没有改变。这些结果强调了番茄中 AsA 池大小的复杂调节。
