Unveiling the evolutionary association of vitamin E, chlorophyll, and PSII through parasitic plants

The evolution of parasitic plants has been marked by a progressive relaxation of selective pressures associated with maintaining photosynthesis, resulting in a wide diversity in photosynthetic capacity within this group. In this study, we explored this diversity by examining several hemi- and holoparasitic plants, focusing on photoprotection. Our findings revealed a strongly conserved evolutionary association between vitamin E, PSII activity, and chlorophyll content in parasitic plants, with α-tocopherol consistently being identified as the predominant vitamin E form. To validate the antioxidant and photoprotective role of α-tocopherol in a plant with reduced photosynthetic capacity, we investigated the interaction between the stem holoparasitic plant field dodder (Cuscuta campestris Yunck.), which retains partial PSII activity and low chlorophyll levels, and its host, lentil plant (Lens culinaris Medik). This protective role, essential for controlling lipid peroxidation within chloroplasts, was demonstrated both in planta and in isolated chloroplasts from field dodder exposed to photoinhibitory conditions induced by the synthetic photosensitizer Rose Bengal and light. Notably, our findings highlight the final evolutionary step in the conserved role of vitamin E in photosynthesis and photoprotection as revealed through parasitic plants.