Genome-wide characterization and transcriptional profiling of the glycerol-3-phosphate acyltransferase (GPAT) family in barley reveals the role of HvGPAT1 in low nitrogen tolerance

Nitrogen (N) deficiency is a prevalent constraint in the agricultural production. A complex crosstalk exists between lipid metabolism and N metabolism. However, the glycerol-3-phosphate acyltransferase (GPAT) family, which is central to plant lipid metabolism, remains poorly characterized in barley, particularly its role in low nitrogen (LN) tolerance. Here, we performed a genome-wide analysis and identified 22 HvGPAT genes unevenly distributed across the seven barley chromosomes. Phylogenetic analysis classified these members into three distinct groups, with those within the same group sharing similar gene structures and conserved motifs. Based on their cis-elements and their phylogenetic relationships with functionally known GPAT homologs, many HvGPATs were predicted to be involved in diverse stress responses. Furthermore, three differentially expressed genes (DEGs) encoding HvGPATs were identified by comparative transcriptome analysis of two barley genotypes with contrasting LN tolerance (LN-tolerant XZ149 and LN-sensitive XZ56) under LN stress. Subcellular localization confirmed that one of these DEGs, HvGPAT1, was localized to the endoplasmic reticulum (ER). Heterologous overexpression of HvGPAT1 in Arabidopsis conferred significant growth advantages under LN stress, whereby barley stripe mosaic virus induced gene silencing (BSMV-VIGS) of HvGPAT1 exacerbated growth inhibition in XZ149 under LN condition. HvGPAT1-mediated alterations reinforced root system development and optimized N assimilation or remobilization, thereby mitigating stress damage. Our findings highlight a positive role of HvGPAT1 in the LN tolerance of XZ149. The HvGPAT DEGs identified in this study represent valuable candidates for investigating the molecular mechanisms of plant LN tolerance.