Seminars

Plant growth is sustained by the activity of meristems at the tips of the plant body. However, meristem organization differs markedly among plant lineages. While seed plant meristems contain multiple stem cells, bryophytes and ferns possess a single stem cell, called the apical cell. How apical cell identity is specified remains largely unknown. In this study, I addressed this question using the gametophore shoot apical meristem of the moss Physcomitrium patens in combination with molecular genetics, live-cell imaging, and single- cell RNA sequencing. These approaches identified apical-cell-specific gene expression and hormonal signaling that determine apical cell identity. Some of the regulatory factors are conserved with those controlling stem cell in seed plants, suggesting that the diversity of stem cell organization evolved through modifications of conserved regulatory networks together with the acquisition of lineage-specific factors.