CLE14 Peptide Impairs Root Tip Regeneration and Callogenesis in Arabidopsis

CLE14 belongs into a family of plant secreted peptides that interact with leucine-rich repeat receptor-like kinase (LRR-RLK) receptors to orchestrate plant morphogenesis. Previous studies indicated that CLE14 plays an important role in cell division, phosphate homeostasis, and senescence, but its specific involvement in cell fate determination and organogenesis remains largely unexplored. Here, through pharmacological, genetic, and cell biology approaches, we show the critical roles for CLE14 in determining the balance between cell division and differentiation in root tip regeneration and callogenesis. Low concentrations of CLE14 or its overexpression in Arabidopsis repressed primary root growth while triggering lateral root and root hair formation. After resection of the primary root tip, CLE14 expression and accumulation were located specifically at the cell layer adjacent to the cutting and at the outermost external cell layer of the root cap as the newly root cap formed. cle14 cr-1 mutants or p35S::amirR-CLE14 lines with reduced levels of CLE14, had comparable root tip regeneration when compared to WT seedlings, whereas 35S::CLE14 seedlings failed to regenerate the missing root tip after resection. The de-differentiation of tissue into proliferative growth was analyzed in WT, cle14 cr-1, and 35S::CLE14 stem explants grown in callus-inducing media. The results showed comparable callus biomass production for WT and cle14 cr-1, but a dramatically reduced callogenesis for 35S::CLE14 explants. Thus, CLE14 acts to repress root tip regeneration as well as callogenesis in Arabidopsis.