Vitamin E helps to control the cellular redox state by reacting with singlet oxygen and preventing the propagation of lipid peroxidation in thylakoid membranes. Both plant ageing and phosphorus deficiency can trigger accumulation of reactive oxygen species, leading to damage to the photosynthetic apparatus. This study investigates how phosphorus availability and vitamin E interact in the control of plant longevity in the short-lived annual Arabidopsis thaliana.
The responses of tocopherol cyclase (VTE1)- and γ-tocopherol methyltransferase (VTE4)-null mutants to various levels of phosphorus availability was compared with that of wild-type plants. Longevity (time from germination to rosette death) and the time taken to pass through different developmental stages were determined, and measurements were taken of photosynthetic efficiency, pigment concentration, lipid peroxidation, vitamin E content and jasmonate content.
The vte1 mutant showed accelerated senescence under control conditions, excess phosphorus and mild phosphorus deficiency, suggesting a delaying, protective effect of α-tocopherol during plant senescence. However, under severe phosphorus deficiency the lack of α-tocopherol paradoxically increased longevity in the vte1 mutant, while senescence was accelerated in wild-type plants. Reduced photoprotection in vitamin E-deficient mutants led to increased levels of defence chemicals (as indicated by jasmonate levels) under severe phosphorus starvation in the vte4 mutant and under excess phosphorus and mild phosphorus starvation in the vte1 mutant, indicating a trade-off between the capacity for photoprotection and the activation of chemical defences (jasmonate accumulation).
Vitamin E increases plant longevity under control conditions and mild phosphorus starvation, but accelerates senescence under severe phosphorus limitation. Complex interactions are revealed between phosphorus availability, vitamin E and the potential to synthesize jasmonates, suggesting a trade-off between photoprotection and the activation of chemical defences in the plants.