A Decoy Library Uncovers U-Box E3 Ubiquitin Ligases That Regulate Flowering Time inArabidopsis

The ubiquitin proteasome system plays an essential role in the regulation of flowering time, a precisely timed developmental transition necessary for plant fitness. However, the full impact... Targeted degradation of proteins is mediated by E3 ubiquitin ligases and is important for the execution of many biological processes. Redundancy has prevented the genetic characterization of many E3 ubiquitin ligases in plants. Here, we performed a reverse genetic screen inArabidopsisusing a library of dominant-negative U-box-type E3 ubiquitin ligases to identify their roles in flowering time and reproductive development. 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 validatePLANT U-BOX 14(PUB14),MOS4-ASSOCIATED COMPLEX 3A(MAC3A), andMAC3Basbona fideregulators of flowering time. This work demonstrates the widespread importance of E3 ubiquitin ligases in floral reproductive development. Furthermore, it reinforces the necessity of dominant-negative strategies for uncovering previously unidentified regulators of developmental transitions in an organism with widespread genetic redundancy, and provides a basis on which to model other similar studies.