Transcription factor which plays a role in mesoderm development, probably by regulating expression of target genes, such as homeobox protein ceh-51 (PubMed:19605496). Binds to DNA consensus motif 5'-[AG]T[GC][GT]CACC[TC][AGCT][AGCT][CT][CT]-3' in promoter elements (PubMed:19605496). Knockout causes abnormal development of the pharynx, when cultured at the restrictive temperature of 23 degrees Celsius, which is exacerbated on a ceh-51 mutant background (PubMed:19605496). Embryonic arrest occurs on a ceh-51 mutant background (PubMed:19605496). Expression of homeodomain protein ceh-51 in embryo is reduced; abolished by simultaneous RNAi-mediated knockdown of pop-1 (PubMed:19605496).