Elevating vitamin C content via overexpression of myo-inositol oxygenase and l-gulono-1,4-lactone oxidase in Arabidopsis leads to enhanced biomass and tolerance to abiotic stresses

Abstract

l-Ascorbic acid (vitamin C) is an abundant metabolite in plant cells and tissues. Ascorbate functions as an antioxidant, as an enzyme cofactor, and plays essential roles in multiple physiological processes including photosynthesis, photoprotection, control of cell cycle and cell elongation, and modulation of flowering time, gene regulation, and senescence. The importance of this key molecule in regulating whole plant morphology, cell structure, and plant development has been clearly established via characterization of low vitamin C mutants of Arabidopsis, potato, tobacco, tomato, and rice. However, the consequences of elevating ascorbate content in plant growth and development are poorly understood. Here we demonstrate that Arabidopsis lines over-expressing a myo-inositol oxygenase or an l-gulono-1,4-lactone oxidase, containing elevated ascorbate, display enhanced growth and biomass accumulation of both aerial and root tissues. To our knowledge this is the first study demonstrating such a marked positive effect in plant growth in lines engineered to contain elevated vitamin C content. In addition, we present evidence showing that these lines are tolerant to a wide range of abiotic stresses including salt, cold, and heat. Total ascorbate content of the transgenic lines remained higher than those of controls under the abiotic stresses tested. Interestingly, exposure to pyrene, a polycyclic aromatic hydrocarbon and known inducer of oxidative stress in plants, leads to stunted growth of the aerial tissue, reduction in the number of root hairs, and inhibition of leaf expansion in wild type plants, while these symptoms are less severe in the over-expressers. Our results indicate the potential of this metabolic engineering strategy to develop crops with enhanced biomass, abiotic stress tolerance, and phytoremediation capabilities.

Modifying Bananas: From Transgenics to Organics?

“…There are additional opportunities, such as: increasing fruit shelf life [33]; increasing abiotic stress tolerance, including drought tolerance [34]; and enhancing bananas as a functional food, for instance by producing banana fruit with increased levels of vitamin C [35], which is likely to increase iron bioavailability.…”

Exogenous ascorbic acid scarcely ameliorates inhibition of photosynthesis in rice leaves by O3

“…Further, it acts as a substance for the synthesis of important organic acids, as well as a cofactor for enzymes involved in multiple processes including flavonoid and phytohormone biosynthesis, and the xanthophyll cycle (Lisko et al, 2013). Several studies reported that exogenous ascorbic acid ameliorated stresses such as salt (Hasanuzzaman et al, 2013), high temperature (Shah et al, 2011), and drought (Malik & Ashraf, 2012).…”

“…Several studies reported that exogenous ascorbic acid ameliorated stresses such as salt (Hasanuzzaman et al, 2013), high temperature (Shah et al, 2011), and drought (Malik & Ashraf, 2012). Lisko et al (2013) showed that an Arabidopsis line overexpressing ascorbic acid biosynthesis enzyme was more tolerant to abiotic stress. In our study, the O 3 inhibition of rice photosynthesis was scarcely ameliorated by ascorbic acid treatment ( Figure 1 and Table 1), although the exogenous ascorbic acid increased ascorbic acid levels at AE-0 (Figure 2).…”

“…Therefore, antioxidant metabolism is an important determination factor for scavenging O 3 injury of plants (Wilkinson et al, 2011). Ascorbic acid is an important non-enzymatic antioxidant in plant tissue that is synthesized by way of sugar metabolism (Lisko et al, 2013). In rice leaves, total ascorbic acid content is increased by chronic O 3 exposure (Nouchi, 1993) and decreased by acute O 3 exposure (Kobayakawa & Imai, 2011a).…”

Plant Stress Physiology

“…Ascorbate accumulation can be increased by over-expression of biosynthesis or recycling enzymes (Smirnoff, 2011). These approaches have produced modest increases in ascorbate along with reported improvements in resistance to various stresses (Lisko et al, 2013). Such results are valuable in providing an understanding of the physiological functions of ascorbate but are more problematic as a basis for crop improvement.…”