Built to rebuild: how plants remake tissue patterns after wounding

Plants have a remarkable ability to regenerate their body parts after injury. In many cases, they make a new meristem after complete loss of stem cells and unique cell types. The pattern that emerges seemingly has few guides and reestablishes without the continuity of events that happen in embryogenesis. We have been working on several systems that examine that process in Arabidopsis root regeneration. I will detail some recent work in which we follow the trajectory of cells that reprogram from one cell fate to another during the repair process. We follow cells using live microscopy and single cell RNA/ATAC-seq methods to ask about the role of cell division and chromatin reorganization. We find that division is a necessary step for complete reprogramming of cell fate but it is not the earliest step. Chromatin closing is required within hours not only to shut down old cell identities but also to moderate a potentially prohibitive stress response. This is in line with other work in the lab that shows how plants, as good as they are at regeneration, are not optimized to regenerate. Rather, they balance defense and regeneration and the two processes are not necessarily completely compatible.