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

A bistable inhibitory optoGPCR for multiplexed optogenetic control of neural circuits

Information is transmitted between brain regions through the release of neurotransmitters from long-range projecting axons. Understanding how the activity of such long-range connections contributes to behavior requires efficient methods for reversibly manipulating their function. Chemogenetic and optogenetic tools, acting through endogenous G-protein-coupled receptor pathways, can be used to modulate synaptic transmission, but existing tools are limited in sensitivity, spatiotemporal precision or spectral multiplexing capabilities. Here we systematically evaluated multiple bistable opsins for optogenetic applications and found that the Platynereis dumerilii ciliary opsin (PdCO) is an efficient, versatile, light-activated bistable G-protein-coupled receptor that can suppress synaptic transmission in mammalian neurons with high temporal precision in vivo. PdCO has useful biophysical properties that enable spectral multiplexing with other optogenetic actuators and reporters. We demonstrate that PdCO can be used to conduct reversible loss-of-function experiments in long-range projections of behaving animals, thereby enabling detailed synapse-specific functional circuit mapping