BnaC4.BOR2 mediates boron uptake and translocation in Brassica napus under boron deficiency

Abstract Boron (B) is an essential microelement in plant growth and development. However, the molecular mechanisms underlying B uptake and translocation in Brassica napus are poorly understood. Herein, we identified a low‐B (LB)‐inducible gene, namely BnaC4.BOR2 , with high transcriptional activity in root tips, stele cells, leaves, and floral organs. The green fluorescence protein labelled BnaC4.BOR2 protein was localised to the plasma membrane to demonstrate the B efflux activity in yeast and Arabidopsis . BnaC4.BOR2 knockout considerably reduced B concentration in the root and xylem sap, and altered B distribution in different organs at low B supply, exacerbating B sensitivity at the vegetative and reproductive stages. Additionally, the grafting experiment showed that BnaC4.BOR2 expression in the roots contributed more to B deficiency adaptability than that in the shoots. The pot experiments with LB‐soil revealed B concentration in leaves and siliques of BnaC4.BOR2 mutants were markedly reduced, showing an obvious B‐deficient phenotype of ‘flowering without seed setting’ and a considerable reduction in seed yield in B‐deficient soil. Altogether, the findings of this study highlight the crucial role of BnaC4.BOR2 in B uptake and translocation during B. napus growth and seed yield under LB conditions.