A model for signal transduction pathways of O2 and UFA regulating OLE1 transcription. X, unknown transcriptional activators acting on the FAR element; M and C, mitochondrial respiratory chain and cytochrome c oxidase, respectively; T, unknown fatty acid transporter located at the cellular membrane. Arrows and blunt arrows, positive and negative interactions, respectively. UFA repression is epistatic to anaerobic derepression (thick line). See Discussion for details.