Abstract
SummaryPatterning in plants relies on oriented cell divisions and acquisition of specific cell identities. Plants regularly endure wounds caused by abiotic or biotic environmental stimuli and have developed extraordinary abilities to restore their tissues after injuries. Here, we provide insight into a mechanism of restorative patterning that repairs tissues after wounding. Laser-assisted elimination of different cells in Arabidopsis root combined with live-imaging tracking during vertical growth allowed analysis of the regeneration processes in vivo. Specifically, the cells adjacent to the inner side of the injury re-activated their stem cell transcriptional programs. They accelerated their progression through cell cycle, coordinately changed the cell division orientation, and ultimately acquired de novo the correct cell fates to replace missing cells. These observations highlight existence of unknown intercellular positional signaling and demonstrate the capability of specified cells to re-acquire stem cell programs as a crucial part of the plant-specific mechanism of wound healing.
Highlights
Multicellular animals and plants emerged well after the split of these two lineages during evolution, and these major eukaryotic groups utilize largely independent mechanisms to deal with challenges of multicellularity, such as cell-to-cell communication, development coordination, and tissue patterning
Restorative Cell Divisions Induced by Local Wounding The root apex of Arabidopsis thaliana proved to be a great model for studying tissue patterning in plants
Once the different cell types are established by the stereotypic, asymmetric cell divisions, the daughter cells undergo only proliferative, anticlinal divisions that propagate the cell files on their way out of the meristem (Figures 1A and 1C)
Summary
Multicellular animals and plants emerged well after the split of these two lineages during evolution, and these major eukaryotic groups utilize largely independent mechanisms to deal with challenges of multicellularity, such as cell-to-cell communication, development coordination, and tissue patterning. Plants as sessile organisms have to regularly endure wounds caused by abiotic or biotic environmental factors; they evolved a remarkable ability to regenerate wounded tissues—e.g., reconnect interrupted vascular strands (Mazur et al, 2016) or regenerate whole complex structures, such as the root apical meristem (Efroni et al, 2016; Sena et al, 2009) It has been known for almost a century that harmed plant tissues activate cell division in adjacent cells and switch division planes to fill the wound with new daughter cells (Hartsema, 1926; Hush et al, 1990; Sinnott and Bloch, 1941). How the tissue re-acquires a correct pattern of cell types and what positional signaling mechanisms contribute to this remain unknown
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