TY - JOUR TI - Negative regulation of conserved RSL class I bHLH transcription factors evolved independently among land plants AU - Honkanen, Suvi AU - Thamm, Anna AU - Arteaga-Vazquez, Mario A AU - Dolan, Liam A2 - Kliebenstein, Daniel J A2 - Hardtke, Christian S. A2 - Shibata, Michitaro A2 - Yamaoka, Shohei VL - 7 PY - 2018 DA - 2018/08/23 SP - e38529 C1 - eLife 2018;7:e38529 DO - 10.7554/eLife.38529 UR - https://doi.org/10.7554/eLife.38529 AB - Basic helix-loop-helix transcription factors encoded by RSL class I genes control a gene regulatory network that positively regulates the development of filamentous rooting cells – root hairs and rhizoids – in land plants. The GLABRA2 transcription factor negatively regulates these genes in the angiosperm Arabidopsis thaliana. To find negative regulators of RSL class I genes in early diverging land plants we conducted a mutant screen in the liverwort Marchantia polymorpha. This identified FEW RHIZOIDS1 (MpFRH1) microRNA (miRNA) that negatively regulates the RSL class I gene MpRSL1. The miRNA and its mRNA target constitute a feedback mechanism that controls epidermal cell differentiation. MpFRH1 miRNA target sites are conserved among liverwort RSL class I mRNAs but are not present in RSL class I mRNAs of other land plants. These findings indicate that while RSL class I genes are ancient and conserved, independent negative regulatory mechanisms evolved in different lineages during land plant evolution. KW - Marchantia polymorpha KW - transcription factors KW - plant development JF - eLife SN - 2050-084X PB - eLife Sciences Publications, Ltd ER -