Tanned or Sunburned: How Excessive Light Triggers Plant Cell Death.

Plants often encounter light intensities exceeding the capacity of photosynthesis (excessive light) mainly due to biotic and abiotic factors, which lower CO 2 fixation and reduce light energy sinks. Under excessive light, the photosynthetic electron transport chain generates damaging molecules, hence leading to photooxidative stress and eventually to cell death. In this review, we summarize the mechanisms linking the excessive absorption of light energy in chloroplasts to programmed cell death in plant leaves. We highlight the importance of reactive carbonyl species generated by lipid photooxidation, their detoxification, and the integrating role of the endoplasmic reticulum in the adoption of phototolerance or cell-death pathways. Finally, we invite the scientific community to standardize the conditions of excessive light treatments. Capturing light intensities exceeding the capacity of photosynthesis can lead to cell death in plant leaves. In this review, the authors summarize recent findings on the mechanisms mediating light-induced cell death, highlighting the roles of reactive carbonyl species, the endoplasmic reticulum, and phytohormones in the adoption of phototolerance versus cell-death pathways. [ABSTRACT FROM AUTHOR]