FIGURE 4.

Photoperiod stress in Arabidopsis. Changes in the photoperiod, i.e., prolongation of the light period, result in a photoperiod stress syndrome, which is characterized by induction of stress response genes, ROS production, accumulation of jasmonic acid (JA) and salicylic acid (SA), and eventually programmed cell death (PCD). Both, cytokinin (CK) (mostly trans-zeatin) and CCA1/LHY are negative regulators of photoperiod stress. Photoperiod stress elicits a transcriptional response that resembles the response to ozone stress and pathogen infection. The resistance to an infection with P. syringae pv. tomato DC3000 is increased after a preceding photoperiod stress event. For more detailed information about the different pathways, please refer to sections “Changes in the Photoperiod Cause Stress” and “Photoperiod Stress Elicits a Similar Response as Pathogen Infection.” The figure has been adapted from Roeber et al. (2021).