The development of the vulva in Caenorhabditis elegans, a soil nematode, is believed to be reliant on the phosphorylation of LIN-31, a winged-helix transcription factor. LIN-31 is part of the Ras/MAP Kinase (MAPK) cell-signaling pathway. When MPK-1, a protein in the Ras/MAPK pathway upstream of LIN-31, is phosphorylated, it enters the nucleus and phosphorylates LIN-31. MPK-1 can phosphorylate any of four consensus sites on the transcription factor, which are a serine or a threonine adjacent to a proline. It is not clear, however, whether or not all four consensus sites are phosphorylated by MPK-1. Understanding this is key to learning more about how LIN-31 affects vulval development. Using PIPE cloning and Gibson Assembly, a “phosphorylation library” of all of the different consensus site combinations was successfully created. This was verified by sequence analysis.