Petunia inflata utilizes a genetic mechanism, self-incompatibility (SI), to avoid self-fertilization and prevent inbreeding. A family of S-Locus F-box (SLF) proteins control pollen function in SI. Our lab hypothesizes that a HECT-type E3 ubiquitin ligase, PiUPL1, mediates degradation of SLF proteins when they are not needed. To test this hypothesis, I will express GFP-fused SLF proteins in PiUPL1 knockout mutants and use biochemical assays to examine their amounts in pollen.