Functions of violaxanthin de-epoxidase-related (VDR) in the photoprotective response to high-light stress

The xanthophyll cycle plays a pivotal role in protecting plants and algae against photodamage. Although the resistance of the violaxanthin de-epoxidase enzyme (VDE) to high light stress in the xanthophyll cycle has been extensively studied, there is limited knowledge about VDE-related (VDR) proteins, which exhibit a close homologous relationship with VDEs. In this study, we preliminary investigated VDR protein, focusing on basic bioinformatics, spatiotemporal gene expression patterns, and high light stress treatment. VDR exhibited a significant homology with VDE, and the CsVDR protein was localized in the chloroplasts. CsVDR was expressed in all tissues of Arabidopsis and cucumber, with the highest expression level observed in mature leaves cultivated for 20 days in cucumber. Interestingly, both CsVDR and AtVDR were identified as high light response genes. Under high light stress, the non-photochemical quenching and Fv/Fm exhibited a decrease in both the Atvdr mutants and TRSV::CsVDR lines compared to the WT. Additionally, the de-epoxidation ratio (A + Z)/(A + Z + V) of the Atvdr mutants was significantly reduced. This suggested that the xanthophyll cycle in Atvdr mutants and TRSV::CsVDR lines were less effective and more susceptible to photoinhibition of PSII under high light stress. Our findings provide compelling evidence for the involvement of VDR proteins in regulating plant response to high light, thereby offering a theoretical basis for further investigation into plant photoprotective pathways.