A Decoy Library Uncovers U-box E3 Ubiquitin Ligases that Regulate Flowering Time in Arabidopsis

Targeted degradation of proteins is mediated by E3 ubiquitin ligases and is important for the execution of many biological processes. Previously, we created and employed a large library of E3 ubiquitin ligase decoys to identify regulators of the circadian clock (Feke et al., 2019). In tandem with the screen for circadian regulators, we performed a flowering time screen using our U-box-type E3 ubiquitin ligase decoy transgenic library. We identified five U-box decoy transgenic populations that have defects in flowering time or the floral development program. We used additional genetic and biochemical studies to validate PLANT U-BOX 14 ( PUB14 ), MOS4-ASSOCIATED COMPLEX 3A (MAC3A), and MAC3B as bona fide regulators of flowering time. This work reinforces the utility of the decoy library in identifying regulators of important developmental transitions in plants and expands the scope of the technique beyond our previous studies.