Light-Induced Degradation and Nocturnal Retrograde Movement of Nonexpressor of Pathogenesis-Related Genes 1 from the Chloroplasts to the Nucleus

This study investigated the complex interplay among circadian rhythms, redox balance, and retrograde signaling in plants, focusing on the role of nonexpressor of pathogenesis-related genes 1 (NPR1). Using transgenic tobacco expressing the NPR1-GFP, we observed circadian oscillations and nuclear accumulation during night and continuous night conditions, suggesting a link between circadian signals and environmental responses of NPR1. We found that NPR1 nuclear localization is influenced by light conditions and the levels of NADPH and NADP⁺, affecting its translocation from the chloroplasts to the nucleus and thereby indicating the circadian gene expression. Our findings on the upregulation of nuclear import components under dark conditions and in NPR1-overexpressing plants shed light on nuclear import processes, indicating the significance of importin proteins in protein translocation. This study enhances our understanding of how plants integrate circadian and redox signals to regulate environmental responses, providing insights into potential strategies for boosting plant resilience via the modulation of the NPR1 pathway.