PAP1

PAP1 stands for Production of Anthocyanin Pigments 1, a gene in Arabidopsis thaliana also known as MYB75. It encodes an R2R3-MYB transcription factor that acts as a key regulator of the plant’s anthocyanin biosynthetic pathway.

As part of the MBW regulatory complex, PAP1 collaborates with a basic helix-loop-helix protein (such as GL3, EGL3, or TT8) and a WD40-repeat protein (TTG1) to activate transcription of late-stage anthocyanin biosynthetic genes. Through this regulation, PAP1 promotes the expression of enzymes including dihydroflavonol 4-reductase (DFR) and leucoanthocyanidin dioxygenase/anthocyanidin synthase (LDOX/ANS), along with related modifying enzymes that lead to the accumulation of anthocyanins and the characteristic purple coloration in tissues.

Expression of PAP1 is influenced by developmental cues and environmental signals, including light, sugar availability, and abiotic stress. Functional studies show that overexpression of PAP1 can induce widespread anthocyanin production, while loss-of-function reduces pigment accumulation under inducing conditions. PAP1 is part of a broader family of R2R3-MYB transcription factors in Arabidopsis, with related members such as PAP2 (MYB90) that have overlapping roles in pigment regulation.

Applications of PAP1 research include metabolic engineering to enhance anthocyanin content in crops and advancing understanding of transcriptional networks that control secondary metabolite production. In other organisms, PAP1 can refer to different genes or proteins, so context is important for interpretation.