Transcriptomic profiling of CRISPR/Cas9-generated mutant of Marchantial polymorpha BES1 transcription factor (Mpbes1)

Brassinosteroid hormones are essential for growth and development in seed plants. In Arabidopsis, transcriptional factors from the AtBES1 (BRI1-EMS-SUPPRESSOR1)/AtBZR1 (BRASSINAZOLE-RESISTANT 1) family, are main regulators of steroid phytohormone Brassinosteroids, which finely coordinate gene expression. While genome sequence analysis in Marchantia polymorpha failed to identify BR receptors homologues to the BRI1-family, a homologue of downstream BR-regulated BES1/BZR1 transcription factors is present. Here, we decipher the biological function of MpBES1 in liverwort. Mpbes1 knock out plants have impaired thallus development, pointing up the conservation of BES1 function in organ development. RNAseq analysis of Mpbes1 reveals a prominent deregulation of oxidation processes, responses to stress and carbohydrate metabolism. Furthermore, in the Arabidopsis orthologs of Mpbes1 deregulated genes, described targets of AtBES1/BZR1 are overrepresented, suggesting a major conservation in the signaling module. In conclusion, this study unravels the origin of BES1/BZR1 family of transcriptional factors in plant cell division. A single-factor (genotype) design was followed: M. polymorpha wild type plants (ecotype Tak-1) were compared to Mpbes-1 mutant plants. Thalli of three different plants per genotype were sampled, constituting three independent biological replicates. Total RNA was extracted but only mRNA was used for sequencing.