PAT1-type GRAS-domain proteins control regeneration following wounding by transcriptional activation of DOF3.4 driving cell proliferation

Plant roots possess a remarkable regenerative potential owing to the presence of stem cells that constantly generate new tissues. Key molecular mechanisms have been linked to this potential, among which the ETHYLENE RESPONSE FACTOR 115 (ERF115) that plays a predominant role in the activation of regenerative cell divisions. However, the downstream operating molecular machinery driving wound-activated cell divisions is largely unknown. Here, we biochemically and genetically identified the GRAS-domain transcription factor protein SCARECROW-LIKE 5 (SCL5) as an interaction partner of ERF115. Although being non-essential under control growth conditions, SCL5 drives redundantly with the related PAT1 and SCL21 transcription factors the expression of the DNA-BINDING ONE FINGER 3.4 (DOF3;4) transcription factor gene. DOF3.4 expression is wound inducible and ERF115 dependent, and in turn activates D3-type cyclin expression. Accordingly, ectopic DOF3.4 expression drives periclinal cell division, whereas its downstream D3-type cyclins are essential for regeneration. The data highlight the importance of the PAT1-branch of GRAS-domain transcription factors for wound activated regeneration processes and pinpoint the DOF3.4 transcription factor as a key element driving regenerative cell divisions. Three biological replicates of root tips of Col-0 or of the triple mutant scl5 scl21 pat1 treated with 0.5ug/ml bleomycin for 24h were compared with three biological replicates of root tips of Col-0 or of the triple mutant scl5 scl21 pat1 under control conditions.