Lateral root formation involving cell division in both pericycle and endodermis is a common and ancestral trait in seed plants

Studies on the model plant Arabidopsis have led to the common view that lateral roots (LR) are exclusively formed from pericycle cells and that the latter have the unique ability to be reprogrammed into stem cells. By analysing lateral root primordium (LRP) formation in an evolutionary context, we show that LRP formation in which both endodermis and pericycle are mitotically activated, is a common and ancestral trait in seed plants, whereas the exclusive involvement of pericycle evolved in the Brassicaceae. Further, also the endodermis can be reprogrammed into stem cells in some species.