Insights into transcription factors (TFs) in non-flowering plants are increading thanks to the establishment of new bryophyte model organisms. In new work, Ishikawa et al. present STEMIN1, a Physcomitrella patens TF belonging to an uncharacterized subgroup of the AP2/ERF family. Physcomitrella undergo cell reprogramming when the leaf is cut, generating chloronema apical stem cells that grow in a filamentous form. STEMIN1 is specifically expressed in regenerating cells, and its overexpression generates ectopic stem cells. Loss-of-function of STEMIN1 and its homologs causes reduced side branching in protonemal growth. This paper provides an in-depth genome-wide analysis of downstream targets of a TF, including RNA-seq and ChiP-seq of the TF and histone marks using an inducible system. The authors show a decrease of H3K27me3 chromatin repressive mark in the promoter regions of STEMIN1-direct target genes, demonstrating how this TF regulates cell-reprogramming through an epigenetic mechanism. It is exciting to see top-notch molecular techniques being applied to early-diverging land plants. (Summary by Facundo Romani) Nature Plants 10.1038/s41477-019-0464-2.
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