Ascorbic acid (AA) is one of the most powerful natural antioxidant able to prevent enzymatic browning after exogenous treatment of minimally-processed products. The specific mechanism by which AA prevents enzymatic browning remains still debated and a direct effect of endogenous AA stimulation and browning has never been studied. The manipulation of AA pathway is a promising approach to study the biochemical mechanism by which AA acts as an anti-browning agent. In this work, cDNA of L-galactono-1,4-lactone dehydrogenase (L-GalLDH), one of the key gene of the Smirnoff–Wheeler’s branch of AA biosynthetic pathway, was isolated and overexpressed in lettuce (Lactuca sativa L. cv ‘Iceberg’), a species highly prone to browning. The hypothesis that the overexpression of L-GalLDH translates to AA accumulation and reduces the browning phenomena in lettuce leaves after cutting was tested. Our results indicate that transgenic lettuce plants, showing about 19-fold overexpression of L-GalLDH as compared to wild type, had about +30 % of AA concentration in mature leaves. Transgenic plants exhibited reduced browning over the leaves, even 10 day after cutting, as demonstrated by higher values of luminosity (L*) and higher values of greenness (a*) compared to control plants. Overall, these findings provide a first evidence of the role of endogenous AA as browning-preventing agent. The obtainment of T2 transgenic lettuce plants is a promising first step to further determine the specific mechanism by which AA acts as an anti-browning preservative.

Overexpression of L-galactono-1, 4-lactone dehydrogenase (L-GalLDH) gene correlates with increased ascorbate concentration and reduced browning in leaves of Lactuca sativa L. after cutting

SALVINI, Mariangela;
2015

Abstract

Ascorbic acid (AA) is one of the most powerful natural antioxidant able to prevent enzymatic browning after exogenous treatment of minimally-processed products. The specific mechanism by which AA prevents enzymatic browning remains still debated and a direct effect of endogenous AA stimulation and browning has never been studied. The manipulation of AA pathway is a promising approach to study the biochemical mechanism by which AA acts as an anti-browning agent. In this work, cDNA of L-galactono-1,4-lactone dehydrogenase (L-GalLDH), one of the key gene of the Smirnoff–Wheeler’s branch of AA biosynthetic pathway, was isolated and overexpressed in lettuce (Lactuca sativa L. cv ‘Iceberg’), a species highly prone to browning. The hypothesis that the overexpression of L-GalLDH translates to AA accumulation and reduces the browning phenomena in lettuce leaves after cutting was tested. Our results indicate that transgenic lettuce plants, showing about 19-fold overexpression of L-GalLDH as compared to wild type, had about +30 % of AA concentration in mature leaves. Transgenic plants exhibited reduced browning over the leaves, even 10 day after cutting, as demonstrated by higher values of luminosity (L*) and higher values of greenness (a*) compared to control plants. Overall, these findings provide a first evidence of the role of endogenous AA as browning-preventing agent. The obtainment of T2 transgenic lettuce plants is a promising first step to further determine the specific mechanism by which AA acts as an anti-browning preservative.
Agrobacterium-mediated transformation Lactuca sativa Ascorbic acid L-galactono-1,4-lactone dehydrogenase
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11384/67179
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