Plant ferritin accumulates in response to photoinhibition but its ectopic overexpression does not protect against photoinhibition

Ferritin is an iron storage protein, involved in iron homeostasis in plant and animal cells. Ferritin could play an important role in protecting cells against the most noxious ROS known, the hydroxyl radicals, whose production is catalysed by Fe(II) and Fe(III). An increased ferritin mRNA abundance was observed in Arabidopsis thaliana leaves photoinhibited with high light at room temperature and also in leaves of A. thaliana plants fumigated with ozone. Very low protein accumulation followed mRNA accumulation in photoinhibited samples. We then investigated the role played by ferritin during photoinhibition or ozone treatment in Nicotiana tabacum and we showed that tobacco lines overexpressing a soybean ferritin gene were not more protected from oxidative stress than the control line. Indeed, at moderate light and chilling temperature, the line overexpressing ferritin in the chloroplast is more affected by a photoinhibitory treatment than its control line and its recovery from stress is impaired.