Boron demanding tissues of Brassica napus express specific sets of functional Nodulin26‐like Intrinsic Proteins and BOR 1 transporters

Summary The sophisticated uptake and translocation regulation of the essential element boron (B) in plants is ensured by two transmembrane transporter families: the Nodulin26‐like Intrinsic Protein ( NIP ) and BOR transporter family. Though the agriculturally important crop Brassica napus is highly sensitive to B deficiency, and NIP s and BOR s have been suggested to be responsible for B efficiency in this species, functional information of these transporter subfamilies is extremely rare. Here, we molecularly characterized the NIP and BOR 1 transporter family in the European winter‐type cv.  Darmor‐ PBY 018 . Our transport assays in the heterologous oocyte and yeast expression systems as well as in growth complementation assays in planta demonstrated B transport activity of NIP 5, NIP 6, NIP 7 and BOR 1 isoforms. Moreover, we provided functional and quantitative evidence that also members of the NIP 2, NIP 3 and NIP 4 groups facilitate the transport of B. A detailed B‐ and tissue‐dependent B‐transporter expression map was generated by quantitative polymerase chain reaction. We showed that NIP 5 isoforms are highly upregulated under B‐deficient conditions in roots, but also in shoot tissues. Moreover, we detected transcripts of several B‐permeable NIP s from various groups in floral tissues that contribute to the B distribution within the highly B deficiency‐sensitive flowers.