Expression profiling of ascorbic acid-related genes during tomato fruit development and ripening and in response to stress conditions

Abstract

L-Ascorbate (the reduced form of vitamin C) participates in diverse biological processes including pathogen defence mechanisms, and the modulation of plant growth and morphology, and also acts as an enzyme cofactor and redox status indicator. One of its chief biological functions is as an antioxidant. L-Ascorbate intake has been implicated in the prevention/alleviation of varied human ailments and diseases including cancer. To study the regulation of accumulation of this important nutraceutical in fruit, the expression of 24 tomato (Solanum lycopersicon) genes involved in the biosynthesis, oxidation, and recycling of L-ascorbate during the development and ripening of fruit have been characterized. Taken together with L-ascorbate abundance data, the results show distinct changes in the expression profiles for these genes, implicating them in nodal regulatory roles during the process of L-ascorbate accumulation in tomato fruit. The expression of these genes was further studied in the context of abiotic and post-harvest stress, including the effects of heat, cold, wounding, oxygen supply, and ethylene. Important aspects of the hypoxic and post-anoxic response in tomato fruit are discussed. The data suggest that L-galactose-1-phosphate phosphatase could play an important role in regulating ascorbic acid accumulation during tomato fruit development and ripening.

Allelic Variation in Paralogs of GDP-l-Galactose Phosphorylase Is a Major Determinant of Vitamin C Concentrations in Apple Fruit

“…However, these QTL explained only a relatively low proportion of the population variability (10%) and were detected only in 1 year. In tomato (Ioannidi et al, 2009) and kiwifruit (Bulley et al, 2009), fruit AsA concentrations were also not correlated with GMP expression. GME has been proposed to be critical for the regulation of plant AsA concentrations by several groups (Wolucka and Van Montagu, 2007;Gilbert et al, 2009), and in tomato, SlGME1 colocates with a cluster of stable fruit AsA-QTL (Stevens et al, 2007), while in apple, MdGME transcript levels are highly correlated with AsA concentrations during apple fruit development (Li et al, 2011).…”

“…The concentration of AsA will be determined by the net rates of biosynthesis, recycling, degradation, and/or intercellular and intracellular transport, but the relative contribution of these various processes depends on several factors, including genetics, tissue type (Bulley et al, 2009), developmental stage (Hancock et al, 2007;Bulley et al, 2009;Ioannidi et al, 2009), and light intensity (Yabuta et al, 2007;Gautier et al, 2009). The biosynthesis of AsA proceeds via L-Gal (Wheeler et al, 1998), although conclusive evidence for all steps has only relatively recently become available (Conklin et al, 2006;Laing et al, 2007).…”

“…Genes involved in several of these mechanisms have been proposed to be key regulators of fruit AsA concentrations, including GDP-L-Gal phosphorylase (GGP) or vitamin c defective2 (VTC2) in kiwifruit (Actinidia deliciosa; Bulley et al, 2009Bulley et al, , 2012 as well as GDP-Man-3,5-epimerase (GME; Gilbert et al, 2009), L-Gal-1-Pphosphatase (GPP or VTC4; Ioannidi et al, 2009), and MDHAR (Stevens et al, 2007) in tomato. However, apart from GGP (Bulley et al, 2012), overexpression of these structural genes has to date had limited success in altering the fruit AsA pool (Agius et al, 2003;Bulley et al, 2009;Haroldsen et al, 2011).…”

Exploring alternative germplasm for the development of stable high vitamin C content in tomato varieties

“…Several aspects explain these large variation levels, with temperature and mainly sun radiation playing a predominant role in ascorbic acid accumulation (reviewed in Dumas et al, 2003). Additionally, oxidative stresses may involve a consumption of l-ascorbic resources to scavenge ROS in post-hypoxic and postanoxic stresses or temperature stresses (Ioannidi et al, 2009). These effects, joined to the genotypic variation typical of wild or traditional populations, might also explain, in a microenvironmental level, the variation found within accession.…”

“…Nevertheless, their success has been limited. Among other factors, it has to be considered that vitamin C content is highly unstable, as it is very sensitive to environmental conditions (Hamner et al, 1945;Hanson et al, 2004) and as expected considering its antioxidant functions, the levels of ascorbic acid are responsive to stress factors (Davey et al, 2000;Ioannidi et al, 2009). Additionally, a deleterious effect of plant yield has been described for this type of high vitamin C cultivars due primarily to a reduction in fruit size (Stevens and 0304-4238/$ -see front matter © 2011 Elsevier B.V. All rights reserved.…”