| Summary: | Plants colonised the land around 470 million years ago. This was facilitated by the acquisition of apical cells capable of dividing in three dimensions, which allowed the development of complex 3-dimensional (3D) morphologies. This is in contrast to the charophyte green algae, from which land plants evolved, which have apical cells that can divide in only 1 or 2 dimensions. Therefore, 3D growth is a pivotal and unifying feature of all land plants, but we know little about how it is regulated. The model moss <em>Physcomitrium patens</em> has been developed as a model system in which to dissect the genetic basis of 3D growth, which also involves complex auxin-cytokinin crosstalk. Previously, a 3D-defective mutant named <em>Ppnog1R</em> was generated in a forward genetics screen. <em>Ppnog1R</em> exhibits cell division orientation defects that result in early developmental arrest of the 3D "shoots" and consequently a complete failure to establish 3D growth. Therefore, 3D growth in <em>P. patens</em> depends on the <em>PpNOG1</em> gene, which encodes a protein with a ubiquitin-associated domain. In this work, the function of <em>PpNOG1</em> was further clarified by genetic manipulation of the <em>Ppnog1R</em> mutant and analysis of the resulting phenotypes. To reveal genetic interactors of PpNOG1, a suppressor screen was performed using an independent nog1 mutant, which yielded two <em>suppressor of nog1</em> mutants (<em>snog1a</em> and <em>snog1b</em>) with restored capacity for 3D growth. The causative mutation in <em>snog1a</em> was mapped and the <em>PpSNOG1A</em> gene was identified as an inhibitor of 3D growth and genetic antagonist of <em>PpNOG1</em>. <em>PpSNOG1A</em> also encodes a protein with a ubiquitin-associated domain. Finally, several RNA-seq experiments were performed, which allowed examination of the transcriptomic landscape of <em>Ppnog1R</em>, another 3D-defective mutant, <em>Ppnog2R</em>, and the snog1a suppressor mutant. These analyses revealed processes and pathways that have been impacted in these mutants.
|
|---|