Considering the alternative pathways for AsA biosynthesis in plants, the effect of fruit shading on the accumulation of representative GalUR transcripts, from the d-galacturonic acid pathway, and MIOX gene, from the 1-d-myo-inositol pathway, were also monitored. The GalUR isoforms investigated in the current study show between 50% and 62% identity at the protein level with the GalUR from strawberry (Supplementary Table S1) that has been demonstrated to play a key role in the regulation of AsA levels in this fruit [11]. Moreover, the GalUR isoforms from Citrus share highly conserved motifs with other GalUR from kiwi and grape (Fig. S1). Interestingly, expression of GalUR8 gene was clearly down- regulated form early stages after fruit covering and the expression level was significantly lower in covered fruit during the whole ripening period (Fig. 3B). However, the expression of GalUR5 and GalUR12 isoforms were essentially unchanged after fruit shad- ing (Fig. 3B). Accumulation of MIOX transcripts was substantially reduced during ripening with very low expression (virtually no expression in November and December) and in shaded fruits this effect was accelerated (Fig. 3 B).