Distress and eustress of reactive electrophiles and relevance to light stress acclimation via stimulation of thiol/disulphide-based redox defences

The involvement of reactive electrophile species (RES) in light stress responses of Chlamydomonas reinhardtii. Excess light increases the formation of singlet oxygen (1O2) from photosystem reaction centres in the chloroplast (green), which can induce lipid peroxidation of the thylakoid membrane lipids. Lipid peroxides decay to release RES (orange) that attack chloroplastic proteins, leading to protein carbonylation, but are also sensed by specific nuclear transcription factors (red), such as SOR1, whereby RES act as chloroplast-to-nucleus retrograde signals. Transcriptional alteration includes up-regulation of transcripts (white italics; black arrows) encoding mechanism that are involved in ROS and RES detoxification (GSTS1, FSD1, NTR3), including increasing glutathione (GSH1) and ascorbate (VTC2) contents. Other defence mechanisms include protecting proteins (HSP22, GRX2, GSTS1) and also mitigating excess light energy (LHCSR1, PSBS), thereby reducing light stress and RES formation. This pathway is superimposed over a false-coloured electron micrograph of an algal cell. The non-coloured region is the cytoplasm.373