Rocks in the Auxin Stream: Wound induced auxin accumulation and ERF115 expression synergistically drive stem cell regeneration

Plants are known for their outstanding capacity for recovering from various wounds and injury. However, it remains largely unknown how plants sense diverse forms of injury and canalize existing developmental processes into the execution of a correct regenerative response. Auxin, a cardinal plant hormone with morphogenlike properties, has been previously implicated in recovery from diverse types of wounding and organ loss. Here, through a combination of cellular imaging and in silico modelling, we demonstrate that vascular stem cell death obstructs the polar auxin flux, much alike rocks in a stream, and causes it to accumulate in the endodermis. This in turn grants the endodermal cells the capacity to undergo periclinal cell division that repopulate the vascular stem cell pool. Replenishment of the vasculature by the endodermis depends on the transcription factor ERF115, a wound inducible regulator of stem cell divisions. Although not being the primary inducer, auxin is required to maintain ERF115 expression. Reversely, ERF115 sensitizes cells to auxin by activating ARF5/MONOPTEROS, an auxin responsive transcription factor involved in the global auxin response, tissue patterning and organ formation. Combined, the wound induced auxin accumulation and ERF115 expression grant the endodermal cells stem cell activity. Our work provides a mechanistic model for wound induced stem cell regeneration in which ERF115 acts as a wound-inducible stem cell organizer that interprets wound-induced auxin maxima. Overall design Three biological replicates of Col-0 root tips treated with 0.5ug/ml bleomycin for 24h were compared with three biological replicates of Col-0 root tips under control conditions