Bryan Thines (University of Puget Sound)| Ashley Brauning (University of Puget Sound)| Amy Replogle (University of Puget Sound)
Gene regulation often depends upon WD40 repeat (WDR) proteins to serve as scaffolds in multi-protein regulatory complexes. For example, WDR proteins can mediate dimerization of DNA-binding transcription factors or they can assist in recruiting additional proteins, such as chromatin-modifying enzymes, required for regulation of gene expression. We have identified two WD40 repeat-like proteins in Arabidopsis that are highly conserved in plants, which we have named FBS INTERACTING PROTEINs (FBIPs) for their interaction with stress-associated E3 ligase SCFFBS. Yeast two-hybrid (Y2H) assays show that FBIP proteins also interact with NIGT1.1, a GARP-type transcriptional repressor that regulates nitrate and phosphate starvation signaling and responses in plants. We further assessed the FBIP-NIGT1.1 interaction with bimolecular fluorescence complementation (BiFC) experiments and found that partnering between these proteins occurs in the nucleus. Our current work investigates whether FBIP proteins interact with other GARP-type repressors, for example the other three members of the NIGT1 family, which could suggest a broader role for FBIP proteins in gene regulation. Collectively, these interactions between SCFFBS, FBIP, and NIGT1 proteins delineate a previously unrecognized SCF-connected transcription regulation module that works in the context of phosphate and nitrate starvation, and possibly other environmental stresses.