Phosphoproteomic analysis of ozone stress-responsive mechanisms in grapevine identifies KEG required for stress regulation.

The environmental damage caused by ozone is of increasing concern globally. The phosphoproteomics approach was used to explore the mechanisms underlying grapevine tolerance to ozone stress and identify phosphoproteins altered by ozone treatment. Results revealed that 194 of 2275 quantitatively analyzed phosphoproteins were significantly regulated after ozone treatment. Biological pathways related to transport were significantly enriched by the differentially regulated phosphoproteins. Among these phosphoproteins, the phosphorylation of RING E3 ligase in grape (V. vinifera KEEP ON GOING, VvKEG) decreased after ozone treatment. Over-expression of VvKEG in Arabidopsis decreased abscisic acid (ABA) sensitivity and enhanced ozone tolerance. Furthermore, VvKEG interacted with the ABA-responsive transcription factor ABSCISIC ACID-INSENSITIVE3 (ABI3). The exogenous application of ABA on grapevine leaves significantly influenced chlorophyll fluorescence, chlorophyll, and malondialdehyde (MDA) contents under ozone treatment; however, treatment with 150 µmol ABA aggravated ozone stress. These results indicate that phosphorylation modification provides information on ozone-induced processes and that VvKEG plays a critical role in these processes via regulation of the ABA signaling pathway in grape.