Carotenoids are involved in the formation of plant leaf color as well as photosystem photoprotection.  This study showed that blue light significantly induced up-regulation of the total carotenoid content in the inner leaves of orange-head Chinese cabbage (OHCC).  Furthermore, the transcriptomic analysis revealed that blue light treatment induced up-regulation of genes in photosynthesis (BrHY5-2, BrCOP1 and BrDET1) and the methylerythritol 4-phosphate pathways (BrGGPS, BrDXS and BrHDR) upstream of the carotenoid metabolic pathway.  Carotenoid metabolomic analysis revealed that the accumulation of several orange and red carotenoids (lycopene, zeaxanthin, β-carotene, lutein, and β-cryptoxanthin) after blue light treatment contributed to the deepening of the leaf coloration, suggesting that short-term blue light treatment could be used to boost nutritional quality.  The light signal gene BrHY5-2 participated in the blue light-induced transcriptional regulation of carotenoid biosynthesis in OHCC.  Overexpression of BrHY5-2 in Arabidopsis significantly increased the total carotenoid content and the sensitivity to blue light.  The above findings revealed new insights about blue-light-induced carotenoid synthesis and accumulation in OHCC lines.  They suggested a new engineering approach to increase the nutritional value of vegetables.

Botryosphaeria dothidea is a destructive fungal pathogen that causes Botryosphaeria canker and fruit ring rot on apple worldwide.  Autophagy is a process of self-degradation that maintains intracellular homeostasis via lysosomal pathway.  To date, the biological role of autophagy in B. dothidea remains unknown.  In this study, we identified and characterized the autophagy-related gene BdATG8 in B. dothidea.  BdATG8 was able to restore the defect in nitrogen starvation tolerance of Saccharomyces cerevisiae ATG8 deletion mutant.  GFP-BdAtg8 was shown to be a useful marker for monitoring autophagy in B. dothidea.  Target deletion of BdATG8 (ΔBdAtg8) blocked autophagy and significantly impaired mycelial growth, conidiation and perithecium formation.  In addition, ΔBdAtg8 showed significantly increased sensitivity to phytoalexin and oxidative stress, suggesting that BdATG8 plays critical roles in overcoming phytoalexin and reactive oxygen species (ROS)-mediated plant immunity.  Pathogenicity assays revealed that ΔBdAtg8 almost lost ability to infect hosts.  Overall, our results indicate that BdATG8 plays an important role in fungal development, stress responses and pathogenesis in B. dothidea.