Highlights d NO GAMETOPHORES 2 (PpNOG2) regulates the 2D to 3D growth transition in P. patens d PpNOG2 regulates gametophore initial cell formation and division plane orientation d PpNOG2 is required for the modulation of the auxin response d PpNOG2 acts upstream of CLAVATA and SCARECROW genes

Figure 1. Haematoxylin and eosin stain showing poorly differentiated polygonal cells containing eccentrically located nuclei and abundant eosinophilic cytoplasm with cells arranged in solid nests. 2. Hep-par stain positivity suggestive of hepatocellular carcinoma. 3. Cytokeratin-7 stain diffusely positive favoring lung as the primary tumor site.

SUMMARYThe colonization of land by plants was one of the most transformative events in the history of life on Earth. The transition from water, which coincided with and was likely facilitated by the evolution of 3-dimensional (3D) growth, enabled the generation of morphological diversity on land. In many plants, the transition from 2-dimensional (2D) to 3D growth occurs during embryo development. However, in the early divergent moss Physcomitrium patens (formerly Physcomitrella patens), 3D growth is preceded by an extended filamentous phase that can be maintained indefinitely. Here, we describe the identification of the cytokinin-responsive NO GAMETOPHORES 2 (PpNOG2) gene, which encodes a shikimate o- hydroxycinnamoyltransferase. In mutants lacking PpNOG2 function, transcript levels of CLAVATA and SCARECROW genes are significantly reduced, excessive gametophore initial cells are produced, and buds undergo premature developmental arrest. Our results suggest that PpNOG2 functions in the ascorbic acid pathway leading to cuticle formation, and that NOG2-related genes were co-opted into the lignin biosynthesis pathway after the divergence of bryophytes and vascular plants. We present a revised model of 3D growth in which PpNOG2 comprises part of a feedback mechanism that is required for the modulation of gametophore initial cell frequency. We also propose that the 2D to 3D growth transition in P. patens is underpinned by complex auxin-cytokinin crosstalk that is regulated, at least in part, by changes in flavonoid metabolism.