N6-Methyladenosine modification of mRNA regulates the transition from 2D to 3D growth in the moss Physcomitrium patens [RNA-seq]

In this study, we identified the main genes of the m6A methyltransferase complex (MTC) in P. patens and we demonstrate that their inactivation by genome editing leads to loss of m6A presence in mRNA and results in defects in the moss life cycle. We detected a delay in the formation of gametophore buds, affecting the transition from 2D to 3D growth and subsequent gametophore formation in all MTC mutant plants. We also observed a defect in spore development, with mutant lines producing reduced-size spores that completely failed to germinate. We performed a genome-wide analysis that revealed several transcripts being affected in the Ppmta background. In addition, we demonstrate that the PpAPB1-4 transcripts, known to be central factors regulating the 2D to 3D transition, are m6A-modified, while in the Ppmta mutant the lack of the m6A mark is associated with a corresponding decrease in their transcript accumulation. Total RNA was isolated from Ppmta mutant and wild type lines and subjected to high throughput sequencing. Two replicates are included.