Michel Havaux - Singlet oxygen signaling mediated by the apocarotenoid b-cyclocitral in Arabidopsis

Abstract Reactive oxygen species (ROS) are inevitable by-products of photosynthesis. In particular, singlet oxygen (¹O₂) is intimately associated with photosynthesis since it is produced from the chlorophyll molecules acting as photosensitizers. The ROS produced in the chloroplasts have a signaling function leading to changes in the expression of nuclear genes to adjust the cellular metabolism to the levels of absorbed light energy. The changes in gene expression associated with ¹O₂ signaling can lead either to cell death or to acclimation to photooxidative stress, depending on the ¹O₂ production levels. Because of its high reactivity and short lifetime, ¹O₂ uses mediators for its signaling. Produced in the chloroplast, the b-carotene derivative b-cyclocitral has been identified as an upstream signal molecule in the ¹O₂ signaling pathway. This talk will summarize our results on the function and mode of action of this apocarotenoid in the acclimation of plants to environmental stresses.