Estimation of the Vitamin C Content and GDP-L-Galactose Phosphorylase Gene (VTC2) Expression Level in Leek (Allium porrum L.) Cultivars

Abstract

In four leek (Allium porrum L.) cultivars, VTC2 homologues cDNAs encoding GDP-L-galactose phosphorylase, a key enzyme of the L-galactose pathway of ascorbic acid (AsA) biosynthesis, were determined. VTC2 cDNA and encoded protein variability in the analyzed cultivars was evaluated. VTC2 expression patterns were defined in the roots, basal plate, pseudostem and leaves of each leek cultivar at three time points: during active growth (August), harvest (October), and after two months of storage (December). It was found that in the roots, VTC2 is expressed in a similar way in all studied cultivars, with the maximum level in October. After two months of storage, a decrease in VTC2 transcription level was observed in the analyzed leek tissues. The AsA content in the cultivars was determined, which positively correlated with the VTC2 expression level in green leaves (r = 0.34), while in white pseudostem, the correlation was negative (r = –0.58). In response to cold stress (+4°C), the VTC2 transcription level in green leaves changed only after 6 h of incubation. After 24 h, in green leaves, VTC2 expression levels and AsA contents were similar to the initial (0 hour) values both ​​under normal conditions and in response to cold stress.