Dehydroascorbate and glucose are taken up into <i>Arabidopsis thaliana</i> cell cultures by two distinct mechanisms

Horemans, Nele; Szarka, András; Bock, Maarten De; Raeymaekers, Tine; Potters, Geert; Levine, Mark; Bánhegyi, Gábor; Guisez, Yves

doi:10.1016/j.febslet.2008.07.001

Cited by 18 publications

(10 citation statements)

References 22 publications

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“…Earlier studies in foliar cell suspension cultures indicate that the preferred uptake form of AsA is as the oxidized form, DHA [13,36]. Our results with young tomato fruits of both cultivars support this, but by the end of ripening at the red stage there was a clear preference for AsA, which increased the size of the totAsA pool 3.3-fold more than incubation with DHA in ‘Santorini’, and 1.4-fold more in ‘Ailsa Craig’.…”

Section: Discussionmentioning

confidence: 99%

Regulation of fruit ascorbic acid concentrations during ripening in high and low vitamin C tomato cultivars

et al. 2012

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BackgroundTo gain insight into the regulation of fruit ascorbic acid (AsA) pool in tomatoes, a combination of metabolite analyses, non-labelled and radiolabelled substrate feeding experiments, enzyme activity measurements and gene expression studies were carried out in fruits of the ‘low-’ and ‘high-AsA’ tomato cultivars ‘Ailsa Craig’ and ‘Santorini’ respectively.ResultsThe two cultivars exhibited different profiles of total AsA (totAsA, AsA + dehydroascorbate) and AsA accumulation during ripening, but both displayed a characteristic peak in concentrations at the breaker stage. Substrate feeding experiments demonstrated that the L-galactose pathway is the main AsA biosynthetic route in tomato fruits, but that substrates from alternative pathways can increase the AsA pool at specific developmental stages. In addition, we show that young fruits display a higher AsA biosynthetic capacity than mature ones, but this does not lead to higher AsA concentrations due to either enhanced rates of AsA breakdown (‘Ailsa Craig’) or decreased rates of AsA recycling (‘Santorini’), depending on the cultivar. In the later stages of ripening, differences in fruit totAsA-AsA concentrations of the two cultivars can be explained by differences in the rate of AsA recycling activities. Analysis of the expression of AsA metabolic genes showed that only the expression of one orthologue of GDP-L-galactose phosphorylase (SlGGP1), and of two monodehydroascorbate reductases (SlMDHAR1 and SlMDHAR3) correlated with the changes in fruit totAsA-AsA concentrations during fruit ripening in ‘Ailsa Craig’, and that only the expression of SlGGP1 was linked to the high AsA concentrations found in red ripe ‘Santorini’ fruits.ConclusionsResults indicate that ‘Ailsa Craig’ and ‘Santorini’ use complementary mechanisms to maintain the fruit AsA pool. In the low-AsA cultivar (‘Ailsa Craig’), alternative routes of AsA biosynthesis may supplement biosynthesis via L-galactose, while in the high-AsA cultivar (‘Santorini’), enhanced AsA recycling activities appear to be responsible for AsA accumulation in the later stages of ripening. Gene expression studies indicate that expression of SlGGP1 and two orthologues of SlMDHAR are closely correlated with totAsA-AsA concentrations during ripening and are potentially good candidates for marker development for breeding and selection.

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Section: Discussionmentioning

confidence: 99%

Regulation of fruit ascorbic acid concentrations during ripening in high and low vitamin C tomato cultivars

et al. 2012

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“…OxT, a major product formed from vitamin C via two oxidation steps, ascorbate → DHA (via ascorbate free radical) and DHA → OxT, largely remained in the apoplastic space of spinach cell‐suspension cultures rather than entering the protoplasm. This finding contrasts with the behaviour of DHA, which does enter the protoplasm (Horemans et al ., ). OxT was only slowly hydrolysed to free OxA in the medium (apoplast) of spinach cell cultures, showing that spinach cells do not secrete appreciable activities of oxalyl esterase into the apoplast.…”

Section: Discussionmentioning

confidence: 97%

Oxalyltransferase, a plant cell‐wall acyltransferase activity, transfers oxalate groups from ascorbate metabolites to carbohydrates

Dewhirst

Fry

2018

The Plant Journal

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SummaryIn the plant apoplast, ascorbate is oxidised, via dehydroascorbic acid, to O‐oxalyl esters [oxalyl‐l‐threonate (OxT) and cyclic oxalyl‐l‐threonate (cOxT)]. We tested whether OxT and cOxT can donate the oxalyl group in transacylation reactions to form oxalyl‐polysaccharides, potentially modifying the cell wall. [oxalyl‐14C]OxT was incubated with living spinach (Spinacia oleracea) and Arabidopsis cell‐suspension cultures in the presence or absence of proposed acceptor substrates (carbohydrates). In addition, [14C]OxT and [14C]cOxT were incubated in vitro with cell‐wall enzyme preparations plus proposed acceptor substrates. Radioactive products were monitored electrophoretically. Oxalyltransferase activity was detected. Living cells incorporated oxalate groups from OxT into cell‐wall polymers via ester bonds. When sugars were added, [14C]oxalyl‐sugars were formed, in competition with OxT hydrolysis. Preferred acceptor substrates were carbohydrates possessing primary alcohols e.g. glucose. A model transacylation product, [14C]oxalyl‐glucose, was relatively stable in vivo (half‐life >24 h), whereas [14C]OxT underwent rapid turnover (half‐life ~6 h). Ionically wall‐bound enzymes catalysed similar transacylation reactions in vitro with OxT or cOxT as oxalyl donor substrates and any of a range of sugars or hemicelluloses as acceptor substrates. Glucosamine was O‐oxalylated, not N‐oxalylated. We conclude that plants possess apoplastic acyltransferase (oxalyltransferase) activity that transfers oxalyl groups from ascorbate catabolites to carbohydrates, forming relatively long‐lived O‐oxalyl‐carbohydrates. The findings increase the range of known metabolites whose accumulation in vivo indicates vitamin C catabolism. Possible signalling roles of the resulting oxalyl‐sugars can now be investigated, as can the potential ability of polysaccharide oxalylation to modify the wall's physical properties.

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“…(2007, 2008) showed how a number of different signals, including extracellular ROS, pH, growth rate and Ca 2+ influx, may be integrated to maintain Ca 2+ [cytosolic] oscillations at 2–4 min −1 in root hair tips. Input signals, such as ROS production from Ca 2+ ‐dependent NADPH oxidase, and, as recent results suggest, Ca 2+ ‐dependent uptake of DHA (Horemans et al. , 2008) could be involved in the generation of a higher frequency signal as Ca 2+ [cytosolic] starts to increase.…”

Section: Discussionmentioning

confidence: 99%

“…(1993), by contrast, claimed the preferential uptake of ascorbate. In plants, DHA transport has been shown to be independent of glucose transport (Horemans et al. , 2008), unlike in mammals (Vera et al.…”

Section: Introductionmentioning

confidence: 99%

Reactive oxygen species‐induced release of intracellular ascorbate in plant cell‐suspension cultures and evidence for pulsing of net release rate

Parsons

Fry

2010

New Phytologist

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Summary Apoplastic ascorbate has been proposed to confer resistance to oxidative stresses, e.g. ozone. We investigated reactive oxygen species (ROS)‐induced secretion and catabolism of ascorbate. Late‐growth‐phase cultured cells of rose and Arabidopsis were preloaded with [14C]ascorbate. Radiolabelled metabolites and secretion products were analysed by high‐voltage electrophoresis. In both species, exogenous 1 mM hydrogen peroxide (H2O2) rapidly stimulated [14C]ascorbate and [14C]dehydroascorbate accumulation in the medium (apoplast). Net 14C export was most rapid within 100 s of washing, and often showed superimposed pulses, of c. 10‐s duration, whose amplitude was greater after H2O2 treatment. Oxidative stress did not cause indiscriminate metabolite leakage from the cells. H2O2 caused c. 20–40% of the intracellular [14C]ascorbate to be irreversibly catabolized to [14C]oxalyl‐threonate and related products; however, the great majority of the extracellular radioactivity remained as [14C]ascorbate and [14C]dehydroascorbate. Much of the apoplastic dehydroascorbate was probably reabsorbed by the cells and reduced back to ascorbate. The data show that exported ascorbate can serve an apoplastic antioxidant role in these late‐growth‐phase cells without being irreversibly lost, whereas in early‐growth‐phase cells most extracellular ascorbate is irreversibly degraded. In conclusion, cultured plant cells can respond actively to oxidative stress by reversibly exporting ascorbate into the apoplast.

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Dehydroascorbate and glucose are taken up into Arabidopsis thaliana cell cultures by two distinct mechanisms

Cited by 18 publications

References 22 publications

Regulation of fruit ascorbic acid concentrations during ripening in high and low vitamin C tomato cultivars

Regulation of fruit ascorbic acid concentrations during ripening in high and low vitamin C tomato cultivars

Oxalyltransferase, a plant cell‐wall acyltransferase activity, transfers oxalate groups from ascorbate metabolites to carbohydrates

Reactive oxygen species‐induced release of intracellular ascorbate in plant cell‐suspension cultures and evidence for pulsing of net release rate

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