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Single-cell disection of Lateral Root ontogeny

Root system formation is essential for the survival and adaptation of plants to the environment. Lateral roots (LR) form the bulk of the mature root systems; however the formative process that generates these new organs (such as their tissues and organization) is not resolved. To study this formative process, we have performed Single-cell RNA-sequencing analysis of the LR primordium in the early stages of development, when tissues are initiated. Our results lead to a model in which seven functionally related cell populations give rise to the main LR tissue lineages through three developmental trajectories that branch sequentially from an initial population of primordial cells. This population of precursor cells rapidly reprograms and splits into two types of cells, one with vascular characteristics and another with stem cell features. We observed that the cells with vascular identity rapidly specialize and locate on the right/left sides of the LR primordium, adjacent to the phloem of the primary root, likely establishing a direct connect to nurture the LR developing tissues. Populations with stem cell characteristics are located in the central area of the LR primordium and subsequently initiate the cells that give rise to the stem cell organizer or quiescent center. In parallel, some of the remaining initial primordial cells generate the LR primordium flanks, while the rest create a reservoir of pluripotent cells able to replace the LR if damaged. In this study, we also generated specific fluorescent biomarkers and analyzed them through confocal microscopy, which confirmed the ontogeny of the LR. In addition, we performed laser ablation experiments and analyzed mutants that showed that cell identities are initiated following a conserved interconnected sequence within each developmental trajectory. Finally, our functional predictions show the role of camalexin, a secondary metabolite regulator of cell division, in cell fate specification during the early stages of the LR primordium formation. Our research reveals how the cell lineages that give rise to the main LR tissues are initiated establishing their functional relationships. It is important to note that LR ontogeny involves hierarchical states of formation, thus differing from embryogenesis, root regeneration and growth.


Original Paper:

Serrano-Ron, L., Perez-Garcia, P., Sanchez-Corrionero, A., Gude, I., Cabrera, J., Ip, P.-L., Birnbaum, K.D., Moreno-Risueno, M.A. 2021. RECONSTRUCTION OF LATERAL ROOT FORMATION THROUGH SINGLE-CELL RNA-SEQ REVEALS ORDER OF TISSUE INITIATION. Molecular Plant. DOI: 10.1016/j.molp.2021.05.028

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