A critical suppression feedback loop determines soybean photoperiod sensitivity.

Photoperiod sensitivity is crucial for soybean flowering, adaptation, and yield. In soybean, photoperiod sensitivity centers around the evening complex (EC) that regulates the transcriptional level of the core transcription factor E1, thereby regulating flowering. However, little is known about the regulation of the activity of EC. Our study identifies how E2/GIGANTEA (GI) and its homologs modulate photoperiod sensitivity through interactions with the EC. During long days, E2 interacts with the blue-light receptor flavin-binding, kelch repeat, F box 1 (FKF1), leading to the degradation of J/ELF3, an EC component. EC also suppresses E2 expression by binding to its promoter. This interplay forms a photoperiod regulatory loop, maintaining sensitivity to photoperiod. Disruption of this loop leads to losing sensitivity, affecting soybean's adaptability and yield. Understanding this loop's dynamics is vital for molecular breeding to reduce soybean's photoperiod sensitivity and develop cultivars with better adaptability and higher yields, potentially leading to the creation of photoperiod-insensitive varieties for broader agricultural applications. [Display omitted] • E2 and FKF1 form a complex to degrade evening complex component J • LUX and J bind to E2 gene body to inhibit its transcription • E2 and EC are crucial members in regulating photoperiod sensitivity Photoperiod sensitivity, essential for crop adaptation and productivity, is regulated in soybean by a feedback mechanism demonstrated by Zhao et al. where E2 and FKF1 degrade the evening complex, and the evening complex suppresses E2 transcription. This feedback loop is critical for establishing soybean's sensitivity to photoperiod. [ABSTRACT FROM AUTHOR]