• Arabidopsis
• cryptochromes
• GWAS
• high light
• PLPB
• vitamin C

Ascorbic acid, or vitamin C, is one of the most abundant molecules in plant cells and plays an essential role in multiple processes, including ROS scavenging, cell signalling and enzyme catalysis. Here, we aimed at identifying and characterizing the genes which are involved in the regulation of ascorbic acid levels in Arabidopsis thaliana. For this purpose, ascorbic acid concentration in the leaves of 300 different accessions of A. thaliana was measured by HPLC and a genome-wide association study (GWAS) was performed. Some of the most statistically significant polymorphisms were located in the gene sequence of a putative blue light receptor. This was shown to interact in vitro and in vivo with VITAMIN C DEFECTIVE 2 (VTC2), a critical enzyme involved in ascorbic acid biosynthesis.
To further investigate the role of blue light in the regulation of ascorbic acid levels, the concentration of vitamin C in leaves of A. thaliana treated either with white light or blue light were compared. In addition to the wild-type genotype, several mutants were grown, including knock-out lines of well-known photoreceptors. The results showed that vitamin C is significantly higher in the blue light treated plants for all the genotypes, excluding a mutant, for which there was no difference between the light treatments.
In conclusion, our experiments indicate that blue light strongly influences ascorbic acid levels in A. thaliana. We collected evidence suggesting an important role of blue light receptors in vitamin C biosynthesis and proposed possible molecular mechanisms through which they may act.