Induction of uncharacterized NRT2 genes by high-pH stress in barley

In plants, nutrient uptake and root elongation typically depend on acidic conditions in the root apoplast. High pH impairs these processes, posing a significant challenge for crop growth in alkaline soils. Barley is widely recognized for its alkaline tolerance. We previously demonstrated that it maintains root elongation under high pH conditions, in contrast to many other plant species. This suggests that barley possesses an unknown mechanism enabling root growth under alkaline stress. In this study, we conducted transcriptome analysis of the root tips, including the apical meristem, of barley cultivar Ehimehadaka No. 1 exposed to high pH. We identified rapid and sustained induction of high-affinity nitrate transporter (NRT2) genes in response to high pH. The cultivar possesses at least 10 NRT2 genes, and three genes from a previously uncharacterized phylogenetic clade showed rapid and consistent upregulation in both the root tip and upper root regions. These NRT2 genes were downregulated under nitrogen-deficient conditions, suggesting that their high pH-induced expression is not simply a result of reduced nitrate uptake. Notably, nitrate uptake was initially suppressed under high pH but rapidly recovers and was maintained at pH 8, indicating that this cultivar can sustain nitrate acquisition even under proton-deficient conditions. Our findings suggest that NRT2 gene induction may contribute to barley’s ability to adapt to high pH environments.