Genome-wide identification of boron transporter NOD26-like intrinsic protein (NIP) and BOR families in soybean (Glycine max), and functional analysis of GmBOR1-1, GmBOR1-5, and GmBOR1-7 in Arabidopsis

Boron (B) is an essential micronutrient for normal plant development. Plants rapidly regulate B uptake and transport through two families of transmembrane transporter proteins: the nodulin 26 (NOD26)-like intrinsic proteins (NIPs) and the B transporters (BORs). Although the NIPs and BORs have been widely characterized across diverse species, a comprehensive analysis of these transporters in soybean ( Glycine max ) remains relatively limited. In this study, 19 GmNIP and 12 GmBOR genes were identified through a genome-wide search. Phylogenetic analyses revealed that these genes exhibited relatively conserved protein motifs and gene structures. Promoter regions of the GmNIP and GmBOR genes harbor numerous cis -elements associated with stress and signaling responses, plant growth and development. Expression profiling across multiple tissues and under varying external boron conditions revealed diverse expression patterns among members of both the GmNIP and GmBOR families. In addition, GmNIP5-1, GmNIP5-2, GmNIP6-5, GmBOR1-1, GmBOR1-5, and GmBOR1-7 proteins were localized to the plasma membrane. Moreover, overexpression of GmBOR1-5 and GmBOR1-7 in the Arabidopsis bor1-5 mutant fully rescued the B-deficiency phenotypes. In summary, our study provides a systematic analysis of boron transporter gene families in soybean, revealing substantial diversity among the GmNIP and GmBOR family members. Notably, GmBOR1-5 and GmBOR1-7 play pivotal roles in boron transport. These genes represent valuable candidates for future functional characterization and will advance our understanding of boron transport mechanisms in soybean.