Bioinformatics and expression analysis of the NRL gene family in Populus trichocarpa

Populus trichocarpa (black cottonwood) is a fast-growing deciduous tree from the willow family (Salicaceae) grown for its fiber products and timber. Phototropism plays a substantial role in the growth, development, and survival strategies of poplar during stress responses. NPH3 (NONPHOTOTROPIC HYPOCOTYL 3) and RPT2 (ROOT PHOTOTROPISM 2), two members of the plant-specific NRL (NPH3/RPT2-like) gene family, are involved in phototropism. Although the NRL gene family has been characterized in most plant species with varying gene family sizes, the whole genome analysis of the NRL gene family in poplar has not been reported. In this study, 78 NRLs were identified, and their conserved domains and gene structures were meticulously characterized in poplar. Many cis-elements associated with plant growth and development, phytohormones, and stress receptiveness were identified in the promoters of PtNRLs. Phylogenetic and interaction network analyses indicated that the role of PtNRLs is evolutionarily conserved in Arabidopsis, rice, and poplar. To summarize, this research presents a detailed clarification of PtNRLs. It forms a basis for the functional analysis of PtNRL gene function and provides a reference for PtNRL gene family data.