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The levels of boron-uptake proteins in roots are correlated with tolerance to boron stress in barley
- Mishra, Sasmita, Heckathorn, Scott, Krause, Charles
- Crop science 2015 v.55 no.4 pp. 1741-1748
- Hordeum vulgare, antibodies, barley, biomarkers, biomass, boric acid, boron, cultivars, enzyme-linked immunosorbent assay, genotype, growth and development, nutrient deficiencies, nutrient excess, nutrient uptake, phytoremediation, plant growth, plant stress, plasma membrane, roots, shoots, stress tolerance, toxicity, transporters, xylem
- Boron (B) is an essential micronutrient required for plant growth and development. Recently, two major B-uptake proteins, BOR1 and NIP5;1 have been identified and partially characterized. BOR1 is a high-affinity B transporter involved in xylem loading in roots, and NIP5;1 acts is a major boric-acid channel in the plasma membrane. The aim of the present study was to determine if plant tolerance to B stress is correlated with natural levels of B-uptake proteins in roots. We grew two barley cultivars that differ in tolerance to low and high B (Schooner and Clipper) at three B levels (sub-, near-, and supra-optimal), and then we determined the concentration of BOR1 and NIP5;1 in roots, using ELISA and protein-specific antibodies that we developed. Shoot and root biomass in Schooner decreased at high B, while shoot mass in Clipper decreased in low B. Differences between cultivars in tolerance to B stress were unrelated to the concentration of B in plant tissue or to effects of B on root:shoot mass. BOR1 content per unit total protein and per g root was greater in Clipper compared to Schooner, while NIP5;1 content was greater in Schooner. The estimated activity of BOR1 (B uptake per BOR1) also differed between cultivars, but NIP5;1 activity did not. These results show that whole-plant tolerance to B deficiency and toxicity is correlated with levels of the major B-uptake proteins in roots (BOR1, NIP5;1). Hence, BOR1 and NIP5;1 can potentially be used as biomarkers to identify plant genotypes with enhanced tolerance to B stress (e.g., for agriculture or phytoremediation).