Acts as histone H2A/H2B chaperone in nucleosome assembly, playing a critical role for the correct expression of genes involved in root proliferation and patterning. Required with NRP2 for the maintenance of cell proliferation and differentiation in postembryonic root growth. Involved in both intramolecular and intermolecular somatic homologous recombination. Can form homomeric and heteromeric protein complexes with NRP2. Binds histones H2A and H2B and associates with chromatin in vivo. Ubiquitous. The acidic domain is probably involved in the interaction with histones. No visible phenotype. Double mutant nrp1-nrp2 shows arrest of cell cycle progression at G2/M and disordered cellular organization occurred in root tips resulting in a short-root phenotype (PubMed:17122067). Double mutant nrp1-nrp2 also displays hypersensitive response to DNA damage (PubMed:17122067) and impaired somatic homologous recombination (PubMed:22534127). Belongs to the nucleosome assembly protein (NAP) family.