HvPHR1 as a key gene in maintaining phosphate homeostasis in barley

• Two homologous PHR genes showed constitutive expression patterns with higher transcriptional levels of HvPHR1 in all developmental tissues. • HvPHR1 functioned as a transcription factor via binding PHR1-binding sequence motif and overexpression of HvPHR1 resulted in overaccumulation of Pi in leaf tissues by up-regulating the transcriptional levels of phosphate starvation induced genes. • HvPHR1 underwent artificial selection during barley domestication. Phosphorus is an essential macronutrient for all living organisms. Although it is abundant in the Earth’s crust, inorganic phosphate (Pi)—accessible to plants—is often limited due to the soil’s physicochemical properties. To cope with Pi scarcity, plants have evolved a complex phosphate starvation response network centered around phosphate starvation response proteins (PHRs) to regulate cellular Pi homeostasis. However, a comprehensive understanding of physiological and molecular functions of PHRs in barley ( Hordeum vulgare ) remains elusive. In this study, we identified two homologous PHRs in barley, with HvPHR1 exhibiting higher expression across all developmental stages, suggesting a dominant role. Overexpression of HvPHR1 resulted in necrotic symptoms in mature leaf tips, which correlated with excessive Pi accumulation in leaves. Transcriptome analysis revealed 732 and 307 significantly differentially expressed genes in the roots and leaves, respectively, in the HvPHR1 -overexpressing transgenic line grown under Pi-sufficient conditions. These genes were primarily associated with phosphate starvation responses and phosphate ion homeostasis. Using published exome resequencing data, we identified 12 SNPs in the CDS, introns, and 3’ UTR of HvPHR1 , which were classified into four main haplotypes. Allele frequency analysis revealed that HvPHR1 underwent artificial selection during barley domestication. Furthermore, the nonsynonymous mutation of HvPHR1 did not affect its nuclear localization or transcriptional activation activity. These findings enhance our understanding of the vital role of HvPHR1 in maintaining Pi homeostasis in barley.