To decipher the molecular mechanisms involved in the regulation of AsA content in shaded fruit, the relative expression of key genes from AsA biosynthesis, degradation and recycling was measured in the flavedo of oranges and mandarins during ripening. Under normal light conditions, an induction in the expression of GGP and GPP, and an increment in GalLDH transcripts in December were the most significant changes of the l-galactose biosynthetic pathway in the flavedo of control non-covered Navelina oranges (Fig. 3A). Several genes of this pathway were repressed to different extents in absence of light. The ripening-associated induction of GGP and GPP was considerably reduced by darkness, whereas accumulation of GalLDH transcripts was only lower in covered fruits harvested in December (Fig. 3A).