Transcription factor; part of the gene cluster that mediates the biosynthesis of the glycolipid biosurfactant ustilagic acid (UA) (PubMed:17850255, PubMed:20173069). UA is a secreted cellobiose glycolipid that is toxic for many microorganisms and confers biocontrol activity to U.maydis (PubMed:17850255). Recognizes and binds to the specific 5'-T/G-G/T-C-G-C-A-T-A/T-C/T-C/T-G/A-3' upstream activating sequence found in all promoters of the UA biosynthesis genes (PubMed:20173069). Expression is strongly induced under conditions of nitrogen starvation. Results in complete loss of ustilagic acid production.