Overexpression of the Monodehydroascorbate Reductase Gene from Non-heading Chinese Cabbage Reduces Ascorbate Level and Growth in Transgenic Tobacco

Abstract

L-Ascorbic acid is an important antioxidant in both animals and plants. Monodehydroascorbate reductase is an enzyme involved in regulating the L-ascorbic acid level in plants. Here, we report the cloning of the reductase gene from non-heading Chinese cabbage (Brassica campestris ssp. chinensis Makino) and negative regulation of L-ascorbic acid and dehydroascorbate levels in transgenic tobacco plants expressing the gene under the control of the 35S promoter. The transgenic plants had reduced growth. The transgenic plants had changed the expression of the genes in the D-mannose/Lgalactose pathway, degradation and recycling pathway and the activity of enzymes involved in degradation (ascorbate oxidase and ascorbate peroxidase) or recycling of ascorbic acid (dehydroascorbate reductase and glutathione reductase).

Metabolism and Regulation of Ascorbic Acid in Fruits

“…Although MDHAR also governs AsA regeneration, the expression level of MDHAR does not always coincide with AsA content. Transgenic plans are overexpressing MDHAR to decrease AsA accumulation, while knockdown of MDHAR gene decreases the AsA content [56,58,59]. However, overexpression of acerola MDHAR in tobacco significantly increases AsA content [60].…”

Advances in Understanding and Harnessing the Molecular Regulatory Mechanisms of Vegetable Quality

“…The most important nutritional quality of Brassicaceae is the content of AsA, which can be regenerated from monodehydroascorbate and dehydroascorbate by MONODEHYDROASCORBATE REDUCTASE ( MDHAR ). Overexpression of MDHAR1 from non-heading Chinese cabbage reduces the AsA level and growth in transgenic tobacco ( Ren et al, 2015 ). Additionally, there is a very significant negative correlation between the nitrate content and AsA content in leaf lettuce ( Koyama et al, 2012 ).…”

“…targets of ARF2, CARBON-METABOLISM INVOLVED (GNC) and GNC-LIKE (GNL) are involved in plant greening, flowering time, and senescence (Richter et al, 2013). It has been reported that the constitutive activation of GA signaling is sufficient to suppress arf2 mutant phenotypes, causing increased chlorophyll accumulation and delayed senescence through repression of GNC and GNL (Richter et al, 2013). These and other aspects of different pathways suggest complex crosstalk in multiple phytohormone signals, reflecting their pleiotropic effects on vegetable growth and ripening.…”