Genome-Wide Identification of NAP1 and Function Analysis in Moso Bamboo (Phyllostachys edulis)

The nucleosome assembly protein 1 (NAP1) family is the main histone chaperone of histone H2A–H2B. To explore the function of NAP1 family genes in moso bamboo (Phyllostachys edulis), characterized by extremely rapid growth and a long flowering cycle, we originally conducted a genome-wide analysis of the PheNAP1 gene. The phylogenetic relationship, gene expression pattern, DNA methylation, and histone modification were analyzed. Eventually, 12 PheNAP1 genes were recognized from the Phyllostachys edulis genome, divided into two sorts: the NRP subfamily (four members) and the NAP subfamily (eight members). Highly conserved motifs exist in each subfamily, which are distinct between subfamilies. PheNAP1 was distributed homogeneously on 10 out of 24 chromosomes, and gene duplication contributed significantly to the enhancement of the PheNAP1 gene in the genome. Cis-acting element analysis showed that PheNAP1 family genes are involved in light, hormone, and abiotic stress responses and may play an important role in the rapid growth and flowering. PheNAP1 exhibited the highest expression level in fast-growing shoots, indicating it is closely associated with the rapid growth of moso bamboo. Besides, PheNAP1 can rescue the early-flowering phenotype of nrp1-1 nrp2-2, and it affected the expression of genes related to the flowering pathway, like BSU1, suggesting the vital role that PheNAP1 may take in the flowering process of moso bamboo. In addition, histone modification results showed that PheNAP1 could bind to phosphorylation-, acetylation-, and methylation-modified histones to further regulate gene expression. A sketch appears: that PheNAP1 can accompany histones to regulate fast-growth- and flowering-related genes in moso bamboo. The consequences of this study enrich the understanding of the epigenetic regulation mechanism of bamboo plants and lays a foundation for further studies on the role of the NAP1 gene in Phyllostachys edulis and the function of chromatin regulation in forest growth and development.