Decoding the molecular basis of lateral root stem cell specification in plants: C-fern as a model system.

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To conquer land, vascular plants evolved a sophisticated root system, which consists of primary and lateral roots (LRs). The de novo LR organogenesis represents a major evolutionary innovation, which has provided sessile organisms like plants with the capacity to forage for water and nutrients. The host lab is a pioneer in demonstrating that LR formation requires de novo specification of stem cells inside the primary root. They also discovered that the early stages of LR initiation are regulated by an oscillatory mechanism where the phytohormone auxin plays a major role. Despite these advances, the exact molecular mechanisms underlying lateral root stem cell (LRSC) specification remain largely elusive and it is not known how these mechanisms emerged during plant evolution. To address these fundamental questions, I will use an emerging model system Ceratopteris richardii (C-fern), which is an evolutionary pivotal, yet underexplored model plant. Based on fossil records, ferns and seed plants diverged during the middle Devonian period from a common ancestor suggesting that several key regulators might be conserved among them, despite some differences in their root ontogeny. In C-fern, the formation of LRSCs is clearly visible at the anatomic level. C-fern has ancestral and possibly simpler mechanisms underlying LRSC specification. In this project, I aim to identify key transcription factors controlling LRSC specification in C-fern. To achieve this goal, I will combine my expertise in molecular and developmental biology with multidisciplinary approaches including single cell RNA sequencing, CRISPR/Cas9-based genome editing and top-notch confocal imaging. This project has a strong potential to introduce novel concepts in the field of plant stem cells and their evolution. It will also open new perspectives for me to become an independent researcher in the field of evo-devo of plant stem cells.