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Roach 2022 Abstract Bioblast

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Roach Thomas
Roach Thomas, Baur T, Stöggl W, Kranner I (2022) Retrograde signalling during high light stress involves reactive carbonyl / electrophile species.
Bioblast 2022: BEC Inaugural Conference. In: »Watch the presentation«

Link: Bioblast 2022: BEC Inaugural Conference

Roach Thomas, Baur Theresa, Stoeggl Wolfgang, Kranner Ilse (2022)

Event: Bioblast 2022

Singlet oxygen (1O2) is one of the most reactive of all reactive oxygen species (ROS), which is produced by chlorophyll during photosynthesis, and induces transcriptional changes in the nucleus, far from its reach. Here, using combined molecular, biochemical and physiological approaches, evidence is presented for how reactive carbonyl/electrophile species (RES) are involved in the acclimation of the model unicellular green alga Chlamydomonas reinhardtii to high light. Light stress led to an accumulation of RES, such as 2-propenal (acrolein) and 4-hydroxynonenal (HNE) [1,2], which are released when (1O2-derived lipid peroxides break down [3]. Treating cells with RES stimulated similar responses to high light, including higher tolerance to (1O2, similar patterns of protein carbonylation, and increased levels of glutathione [1,4], an important antioxidant involved in RES detoxification. A RNA seq. analysis revealed clear overlaps in gene regulation between RES-treated and high light-treated cells, which included an upregulation of many antioxidant enzymes and redox-related processes, as well as carotenoid and ubiquinone biosynthesis. However, most prominent was the overlap in down-regulated genes, whereby 70 % of the down-regulated genes under high light were also down-regulated by RES [1]. Moreover, the majority of these were shared when cells were treated with the photosenstizer Rose Bengal as an exogenous (1O2 source, confirming the specific role of (1O2 in RES signalling under high light stress. Finally, a comparison to differential gene expression in response to H2O2 revealed that half of the genes were also differentially expressed in the same direction after treatment with HNE, the only RES that increased upon treatment of cells with the same concentration of H2O2. Therefore, HNE is also a possible pathway for H2O2-mediated signalling.

  1. Roach T, Stoggl W, Baur T, Kranner I (2018) Distress and eustress of reactive electrophiles and relevance to light stress acclimation via stimulation of thiol/disulphide-based redox defences.
  2. Roach T, Na CS, Stöggl W, Krieger-Liszkay A (2020) The non-photochemical quenching protein LHCSR3 prevents oxygen-dependent photoinhibition in Chlamydomonas reinhardtii.
  3. Mano J, Biswas MS, Sugimoto K (2019) Reactive carbonyl species: A missing link in ROS signaling.
  4. Roach T, Baur T, Stoggl W, Krieger-Liszkay A (2017) Chlamydomonas reinhardtii responding to high light: A role for 2-propenal (acrolein).

Keywords: Photosynthesis, Chloroplast, light stress, Retrograde signalling, Reactive Oxygen Species


Department of Botany, University of Innsbruck, Austria


Graphical Abstract 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, 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.

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Event: A2