1. Identification and function characterization of BnaBOR4 genes reveal their potential for Brassica napus cultivation under high boron stress.
- Author
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Liu L, Luo Y, Ding G, Wang C, Cai H, Shi L, Xu F, Bao X, and Wang S
- Subjects
- Boron toxicity, Boron metabolism, Plant Proteins genetics, Plant Proteins metabolism, Membrane Transport Proteins metabolism, Amino Acids metabolism, Soil, Gene Expression Regulation, Plant, Brassica napus metabolism, Arabidopsis genetics, Arabidopsis metabolism
- Abstract
Boron (B) is essential for plant growth, but toxic in excess. In several countries, soil toxic B levels are always a severe agricultural problem in arid and semi-arid regions. Phytoremediation of excess B containing soil is still in its infancy, while high B tolerant plants with elevated protein abundance of B efflux transporter were successfully established or explored. Brassica napus (B. napus) is one of the most important oil crops. However, B efflux transporters underlying excess B tolerance in B. napus remain unknown. Here, we reported that in Brassicaceae species, B. napus had four homologous genes of Arabidopsis AtBOR4 , which were renamed BnaBOR4.1, BnaBOR4.2, BnaBOR4.3 and BnaBOR4.4. BnaBOR4.1, BnaBOR4.2 and BnaBOR4.3 showed constitutive expression and BnaBOR4.4 appeared to be a pseudogene. BnaBOR4.2 and BnaBOR4.3 were expressed in inner cell layers and BnaBOR4.1 in the outer cell layer in root tip, and all were expressed in vascular tissue in the mature zone. B efflux activity assays in yeast demonstrated that BnaBOR4.1, BnaBOR4.2 and AtBOR4 but not BnaBOR4.3 had comparable levels of B transport activity. Structure-functional analysis between BnaBOR4.3 and BnaBOR4.2 demonstrated that amino acid residue substitution at position 297 (Ala vs Pro) and 427 (Met vs Leu) is critical for the B transport activity. Mutant BnaBOR4.3
M427L partially restored the B efflux activity, and both mutants BnaBOR4.3A297P and BnaBOR4.3A297P&M427L fully restored B efflux activity, indicating that the Pro297 residue is critical for their function. Further validation of BnaBOR4 was accomplished by growing transgenic Arabidopsis plants under high B conditions. Taken together, our study identified two functional B efflux genes BnaBOR4.1 and BnaBOR4.2 in B. napus, and a key amino acid residue proline 297 associated with B efflux activity. This study highlights the potential of BanBOR4 genes for B. napus cultivation under high B stress., Competing Interests: Declaration of Competing Interest I declare on behalf of my co-authors that the work described is an original research that has not been published previously, and the manuscript has not been under consideration for publication elsewhere, in whole or in part. No conflict of interest exits in the submission of this manuscript, and the manuscript has been approved by all the authors for publication., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)- Published
- 2024
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