Changes in Ascorbate Content and Its Metabolism Gene Expression Pattern in Garlic Allium sativum L. Leaves in Response to Cold Stress

In two winter garlic (Allium sativum L.) cultivars, the expression of genes encoding key enzymes of the L-galactose pathway of ascorbate (AA) biosynthesis (VTC2, GPP, GalDH, GalLDH) and genes encoding AA recycling from oxidized forms (MDHAR1, MDHAR4, MDHAR5) was determined in the dynamics (0, 2, 4, 6, and 24 h) of short-term (24 h) cold (2°C) stress. It was found that in the leaf tissue of both cultivars (Sarmat and Dubkovsky), the level of VTC2 transcripts steadily increased during stress. The cultivars are also similar in the expression response to stress of the GalLDH and MDHAR1 genes, but differ in the reaction of the GPP, GalDH, MDHAR4 and MDHAR5. In the leaf tissue of both cultivars, the content of AA, carotenoids (total) and chlorophylls (a and b) was determined in the dynamics of cold stress. It was shown that the amount of all analyzed metabolites is initially higher in the cv. Sarmat than in the cv. Dubkovsky, and changes in the stress dynamics in a cultivar-specific manner. A positive correlation was shown between the amount of AA and the level of expression of the GalDH gene for both cultivars.