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Analysis of physiological responses and expression profiling of boron transporter-like genes in response to excess boron in Populus russkii

Ou, Yongbin, Wu, Xiuli, Gao, Yongfeng, Wu, Yingqing, Yao, Yinan
Chemosphere 2019 v.224 pp. 369-378
Populus, antioxidant activity, boron, cytoplasm, genes, leaves, physiological response, phytoremediation, plant growth, polluted soils, proline, toxicity, yeasts
Poplars (Populus species) are tolerant to boron (B) toxicity and have phytoremediation potential in B-contaminated soils. However, the detoxification strategy is largely unknown. To screen the key B transporter-like (BOR-like) genes for B compartmentation, Populus russkii plants were exposed to different levels of excess B and the plant growth, physiological responses, B distribution, and the expression patterns of BOR-like genes were characterized. P. russkii showed moderate tolerance to excess B although the plant growth was inhibited. The enhanced proline level and well-regulated antioxidant defense system were associated with B tolerance in leaves. The B absorbed by plants was predominantly allocated to leaves. Ten BOR-like genes were identified and seven of them showed tissue-specific expression patterns. PrBOR7 was identified as an important BOR-like gene possibly involved in the export of B from leaf cytoplasm because it was expressed specifically in leaves and induced by excess B. Yeast experiment assays verified that PrBOR7 functions as an efflux-type transporter and strongly improved cell tolerance to excess B. The expression patterns of BOR-like genes highlight the diversity of the family members in P. russkii, and PrBOR7 has potential as a candidate gene for B detoxification.