Phytohormonal cell cycle control in the plant root meristem

Phytohormones are central endogenous regulators that govern essential cellular processes such as cell division and differentiation, ultimately determining plant growth and development. In addition to their individual contributions to core cell cycle events, the interplay and signaling interdependencies between phytohormones are crucial for coordinated cell cycle progression. These interactions fine- tune both the rate of cell division and the timing of cell cycle transitions. Although the hormonal control of the plant cell cycle has been previously explored, recent technological advancesparticularly single-cell genomics and live imagingallow for unprecedented, high-resolution insights into hormone dynamics at the single-cell level. Applying these tools, we have identified stage-specific fluctuations in auxin, cytokinin, and brassinosteroid signaling throughout the cell cycle. Specifically, auxin and brassinosteroid signaling decrease during mitosis and resume in the G1 phase, whereas cytokinin activity peaks during the G2-to-M transition. These findings highlight temporally distinct roles for each hormone and emphasize the complex, coordinated nature of their signaling during cell cycle regulation. This collaborative project aims to dissect the molecular framework governing this coordination by integrating long-term confocal imaging, single-cell RNA sequencing, phosphoproteomics, and metabolite profiling. Focusing on root meristematic cells of Arabidopsis thaliana, we seek to unravel the mechanisms driving hormonal crosstalk and their integration into the plant cell cycle machinery. The proposed research represents a novel and comprehensive approach to decoding the phytohormonal regulation of the plant cell cycle. Through the synergistic expertise of two research groups specializing in auxin, cytokinin, and brassinosteroid biology, and supported by cutting-edge methodologies, this project offers an ambitious yet feasible strategy to advance our understanding of hormone-controlled growth regulation in plants.