A αTub84B promoter drives expression of a bicistronic transcript that encodes two open reading frames separated by a 2A self-cleaving peptide (to ensure separate translation of each protein). The first ORF encodes Atha\TIR1 carrying two point mutations (D170E and M473L) that improve substrate affinity and auxin sensitivity (details from PMID:26552885). The second ORF encodes GAL80 tagged with Tag:degron(AID) (minimal degron sequence has been used). In the absence of auxin, Tag:degron(AID)-tagged GAL80 is produced, which can repress GAL4 activity. In the presence of auxin, the Tag:degron(AID) degron tethers the tagged GAL80 protein to the Atha\TIR1 protein, triggering the degradation of GAL80 protein and allowing GAL4-mediated expression.