Fig 1.
L-ascorbic acid biosynthesis by the L-galactose pathway (A) and the ascorbate-glutathione cycle (B) in plants. The enzymes catalyzing the reactions are as follows: glucose-6-phosphate isomerase (GPI), mannose-6-phosphate isomerase (PMI), phosphomannomutase (PMM), GDP-mannose pyrophosphorylase (GMP), GDP-mannose-3′,5′-epimerase (GME), GDP-L-galactose phosphorylase (GGP), L-galactose-1-phosphate phosphatase (GPP), L-galactose dehydrogenase (GalDH), L-galactono-1,4-lactone dehydrogenase (GalLDH), ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), ascorbate oxidase (AO), and glutathione reductase (GR).
Table 1.
Standard primers used for gene cloning.
Table 2.
Standard primers used for mRNA expression.
Fig 2.
Changes in ascorbic acid (AsA) accumulation levels during fruit development.
(A) Total AsA (T-AsA), AsA, and dehydroascorbate (DHA) concentrations based on fresh weight of fruit; (B) T-AsA and AsA content per fruit; (C) AsA/DHA ratio. T-AsA and AsA content per fruit was obtained by multiplying average fruit weight by concentration based on fresh weight.
Table 3.
Genbank homology search results for cloned sequences in this study.
Fig 3.
Changes in relative mRNA expression for genes encoding enzymes involved in the L-galactose pathway of ascorbic acid synthesis, including GP1, PMI, PMM, GMP, GME, GPP, GGP1, GGP2, GalDH, and GalLDH.
Fig 4.
Changes in relative mRNA expression for genes encoding enzymes involved in ascorbic acid degradation and recycling during fruit development, including AO1, AO2, APX1, APX2, APX3, GR1, GR2, MDHAR, DHAR1, and DHAR2.
Fig 5.
Changes in relative mRNA expression for genes encoding enzymes involved in ascorbic acid synthesis and recycling in young, mature, and old leaves.
(A) GPI, PMI, PMM, GMP, GME, GGP1, GGP2, GPP, GalDH, and GalLDH; (B) AO1, AO2, APX1, APX2, APX3, DHAR1, DHAR2, MDHAR, GR1, and GR2; (C) ascorbic acid (AsA) accumulation levels in old leaves, mature leaves, and young leaves.
Fig 6.
Changes in enzyme activity levels of (A) GalLDH and GalDH; (B) MDHAR, DHAR, and GR; (C) APX, based on fresh weight during fruit development.