The Concentration of Nutrient-Uptake Proteins in Plant Tissue Can be Used to Identify Genotypes with Desirable Nutrient-Relations Traits.

Root mineral nutrient uptake from soil involves nutrient-uptake proteins (NUPs), which are potential targets to improve crop nutrient-uptake and food quality. To explore the use of NUPs as biomarkers for crop improvement, we measured NUP concentration in roots of cultivars of barley (Hordeum vulgare), using protein-specific antibodies, to determine (1) if levels of the two main types of NO₃^--uptake proteins (NRT1, NRT2) and the main type of NH₄⁺-uptake protein (AMT1) are correlated with tissue nitrogen concentration (%N); and (2) if levels of the two main boron-uptake proteins (BOR1 and NIP5;1) are correlated with tolerance to B stress. The concentration of all three N-uptake proteins was positively correlated with shoot and root %N, especially levels per g root of NRT1 and NRT2 with root %N and AMT1 with shoot %N. Also, levels of BOR1 and NIP5;1 were correlated with tolerance to B toxicity and deficiency. Hence, total NUP concentrations in tissue may be useful biomarkers in identifying crop cultivars with desirable nutrient-relations traits.