This dataset contains quantitative co-immunoprecipitation mass spectrometry (Co-IP-MS) data generated to investigate direct interactions between the Arabidopsis co-regulator LUH and the MADS-domain transcription factor AP1. LUH wild type and domain variants (LUH_W, LUH_QW, LUH_LQ) were co-expressed with AP1 or empty vector controls, and proteins were immunoprecipitated using AP1-specific antibodies. Input and eluate fractions were analyzed by LC-MS/MS and quantified using MaxQuant. The results show that LUH interacts directly with AP1 via its C-terminal domains, supporting a distinct mode of co-regulator-MADS TF association.