## 2 Results
### Transcriptional Analysis of Genes Involved in the AsA Metabolic Pathways
In leaves, most genes decreased in their relative expression with leaf development (Figure 5). A slight reduction was detected for the genes of the L-galactose pathway, while a marked down-regulation was observed for _GalUR8_, _GalUR10_, _GalUR12_, and _GalUR17_ of the D-galacturonic acid pathway (Figure 5A). For the genes involved in AsA degradation, only _AO_ and _APX3_ were downregulated (Figure 5B), while _MDHAR3_, _DHAR1_, and _DHAR2_ of the recycling pathway, were also repressed during leaf development (Figure 5C). It is noteworthy that none of the 23 genes analyzed were stimulated or induced during the development of leaves. Figure 5: Relative expression of genes involved in the biosynthesis (**A**), degradation (**B**), and recycling (**C**) of AsA in young (Y) and mature (M) leaves of Valencia Late orange (_Citrus sinensis_). The genes analyzed were _GMP_, _GME_, _GGP_, _GP_, _GalDH_, and _GalLDH_ of the L-galactose biosynthesis pathway; _GalUR5_, _GalUR8_, _GalUR10_, _GalUR12_, _GalUR14_, and _GalUR17_ of the D-galacturonic biosynthesis pathway; _MIX_, of the _myo_-inositol pathway; _AO_, _APX1_, _APX2_, _APX3_, and _APX4_ involved in AsA degradation; and _MDHAR1_, _MDHAR2_, _MDHAR3_, _DHAR1_, and _DHAR2_, involved in AsA recycling. An expression value of 1 was arbitrarily assigned to the values obtained in the flavedo of fruit in June. Results are the mean \(\pm\) S.E. of at least three replicates. 3.2 Transcriptional Analysis of Genes Involved in AsA Metabolism in Flavedo and Pulp during Fruit Development of Valencia Late Oranges  
In fruits, the expression of most genes exhibited a relatively similar temporal profiling in the flavedo and pulp during development, although transcripts levels were in general higher in the flavedo than in the pulp (Figures 6 and 7), in agreement with the differences in AsA concentrations (Figure 3C,D). In the flavedo, the expression of genes of the biosynthetic pathways was very variable. Of the L-galactose pathway, transcripts of _GMP_ and _GalDH_ were higher at early stages of fruits development and slightly decreased in mature fruits, while _GME_ and _GalLDH_ showed minor changes in their expression during development and ripening. However, transcript levels of other genes increased after September-October and remained high (_GPP_) or declined (_GGP_) in the flavedo of mature fruits. Interestingly, genes of D-galacturonic pathway were in general more highly expressed during fruit development, and declined at different rates after October or November, coincidentally with the onset of peel color development. Expression of _MIOX_ was high in the flavedo of fruitlets form June and markedly decreased during the remaining stages of fruit development and maturation (Figure 6A). Figure 6: Relative expression of genes involved in the biosynthesis (**A**), degradation (**B**), and recycling (**C**) of AsA in the flavedo of fruit of Valencia Late orange (_Citrus sinensis_) during fruit development and maturation. Fruits were harvested from  
early development in June (Jn) to overmutative fruit in June of the next year (indicated as Jn*). The genes analyzed were _GMP_, _GME_, _GGP_, _GPP_, _GallDH_, and _GallDH_ of the L-galactose biosynthesis pathway; _GallR5_, _GallR8_, _GallR10_, _GallR12_, _GallR14_, and _GallR17_ of the D-galacturonic bio-synthesis pathway; _MIOX_, of the _mpo_-inositol pathway; _AO_, _APX1_, _APX2_, _GallR14_, and _GallR17_ of the D-galacturonic bio-synthesis pathway; _MIOX_, of the _mpo_-inositol pathway; _AO_, _APX1_, _APX2_, _APX3_, and _APX4_ in-volved in AsA degradation; and _MDHARI_, _MDHAR2_, _MDHAR3_, _DHARI_, and _DHAR2_, involved in AsA recycling. An expression value of 1 was arbitrarily assigned to the values obtained in the flavedo of fruit in June. Results are the mean \(\pm\) S.E of at least three replicates. Figure 7: Relative expression of genes involved in the biosynthesis (**A**), degradation (**B**), and recycling (**C**) of AsA in the pulp of fruit of Valencia Late orange (_Citrus sinensis_) during fruit development and maturation.