The transcription factor OBP 4 controls root growth and promotes callus formation

Summary Plant growth and development require a continuous balance between cell division and differentiation. In root meristems, differentiated cells acquire specialized functions, losing their mitotic potential. Some plant cells, such as pericycle cells, have a remarkable plasticity to regenerate new organs. The molecular mechanisms underlying cell reprogramming are not completely known. In this work, a functional screening of transcription factors identified Arabidopsis OBP 4 (OBF Binding Protein 4) as a novel regulator of root growth and cell elongation and differentiation. Overexpression of OBP 4 regulates the levels of a large number of transcripts in roots, many involved in hormonal signaling and callus formation. OBP 4 controls cell elongation and differentiation in root cells. OBP 4 does not induce cell division in the root meristem, but promotes pericycle cell proliferation, forming callus‐like structures at the root tip, as shown by the expression of stem cell markers. Callus formation is enhanced by ectopic expression of OBP 4 in the wild‐type or alf4‐1 , but is significantly reduced in roots that have lower levels of OBP 4 . Our data provide molecular insights into how differentiated root cells acquire the potential to generate callus, a pluripotent mass of cells that can regenerate fully functional plant organs.