Genome-wide analysis of the HAK/KUP/KT gene family in Spinacia oleracea L.: Insights into potential stress-related regulatory mechanisms

Potassium is an essential macronutrient that contributes to ion homeostasis, protein synthesis, and plant responses to biotic and abiotic stresses. The HAK/KUP/KT gene family plays a key role in regulating potassium uptake and transport in plants. Despite the functional importance of these transporters, this gene family has not yet been comprehensively characterized in Spinacia oleracea. Therefore, this study conducted a genome-wide analysis of HAK/KUP/KT genes in S. oleracea, including chromosomal localization, physicochemical characterization, phylogenetic relationships, gene structure, conserved motifs, secondary and tertiary protein structures, subcellular localization, cis-acting elements, and miRNA target prediction. A total of 32 HAK/KUP/KT genes, designated as SoHAKs, were identified across six chromosomes of S. oleracea. Among these genes, ten were located on chromosome 1, indicating an uneven chromosomal distribution. Phylogenetic analysis classified the SoHAK family into three major groups. Physicochemical characterization revealed that most SoHAK proteins were basic in nature and predicted to be unstable. Structural analyses indicated that most SoHAK proteins contained α-helices, β-strands, and loop regions. Subcellular localization prediction showed that most SoHAK proteins were associated with the plasma membrane, supporting their potential roles in potassium transport. Promoter and miRNA target analyses further suggested that several SoHAK genes may be involved in stress-related regulatory mechanisms. Notably, SoHAK2, SoHAK3, SoHAK4, SoHAK10, SoHAK26, SoHAK27, SoHAK29, SoHAK30, and SoHAK32 emerged as candidate genes for future functional studies. Overall, these findings provide a genomic framework for further investigating the potential roles of HAK/KUP/KT genes in potassium transport and stress-related regulatory mechanisms in S. oleracea.