The influence of growth media pH on ascorbic acid accumulation and biosynthetic gene expression in tomato

•Total ascorbate decreases and AsA/DHA increases in tomato leaves as pH increases.•AsA biosynthetic gene expression negatively correlates with AsA under different pH.•Expression of majority of AsA biosynthetic genes decreases as the pH increases.

The ascorbic acid (AsA) accumulation in plants is affected by various growth, development and environmental factors. The pH of growth media has been reported to affect the accumulation of AsA in plants. In this study, the impact of the pH on the AsA accumulation as well as its biosynthetic gene expression was analyzed in tomato (Solanum lycopersicum 'Ailsa Craig'). The results indicated that with the increase in pH, total AsA content in tomato leaves decreased and redox status (AsA/DHA) was augmented. Similarly, most of the biosynthetic gene expression level decreased with the increment of pH and showed the negative correlation; only a few genes, e.g., genes encoding GDP-Mannose 3′,5′-epimerase 1 (GME1), GDP-l-galactose-1-phosphate phosphorylase 1 (GGP1) and GGP2 showed positive correlation. Moreover, in situ H2O2 was detected which accretion was escalated as the pH value surged from 5.0 to 7.0, in agreement to the decreased AsA level. The present study suggests that mild acidity may contribute to the boosted accumulation of AsA in tomato.