Transcriptional activation of auxin biosynthesis drives developmental reprogramming of differentiated cells

Plant cells exhibit remarkable plasticity of their differentiation states, enabling regeneration of whole plants from differentiated somatic cells. How they revert cell fate and express pluripotency, however, remains unclear. Here we show that transcriptional activation of auxin biosynthesis is crucial for reprogramming differentiated leaf cells in Arabidopsis. We demonstrate that intervention of histone acetyltransferases causes severe defects in callus formation from leaf mesophyll protoplasts. Our data suggest that histone acetylation affects transcription of auxin biosynthesis genes. Auxin biosynthesis is in turn required to accomplish initial cell division through the activation of G2/M phase genes mediated by MYB DOMAIN PROTEIN 3-RELATED (MYB3Rs). We further show that AUXIN RESPONSE FACTOR 7 (ARF7)/ARF19 and INDOLE-3-ACETIC ACID INDUCIBLE 3 (IAA3)/IAA18-mediated auxin signaling pathway is responsible for the cell cycle reactivation in protoplasts. These findings provide novel mechanistic insights into how differentiated plant cells revert their fate and reinitiate the cell cycle to exert pluripotency. Overall design: Expression profiling for fresh and cultured mesophyll protoplasts from Arabidopsis leaves