Chromatin remodeling in Arabidopsis root growth.

The basic structural unit of chromatin is the nucleosome, which consists of 146 bp of DNA wrapped around the histone octamer constituted by two molecules each of histones H2A, H2B, H3 and H4. Nucleosome assembly/disassembly/reassembly processes occur primarily during DNA replication and also during transcription, DNA repair and recombination. Several chromatin-remodeling factors had been previously shown to have pleiotropic roles in different processes of plant growth and development. We have recently demonstrated that the Arabidopsis NRP1 and NRP2 genes encode H2A/H2B chaperones and are required for the maintenance of post-embryonic root growth. The nrp1-1nrp2-1 double mutant plants specifically showed a short-root phenotype in normal growth conditions. They were also hypersensitive to DNA damage and showed release of transcriptional gene silencing. We propose that NRP1 and NRP2 act as histone H2A/H2B chaperones in nucleosome assembly, playing critical roles for a correct genome transcription in the maintenance of root growth.