Genome-Wide Identification and Abiotic Stress Response Analysis of the Isopentenyl Transferase (IPT) Gene Family in Soybean (Glycine max L.)

Isopentenyltransferase (IPT) is the rate-limiting enzyme in cytokinin biosynthesis and plays a critical role in plant acclimation to abiotic stress. To explore soybean <i>IPT</i> genes, we performed genome-wide identification, bioinformatics analysis, and molecular experimental validation to systematically characterize the features and functions of the soybean <i>IPT</i> (<i>GmIPT</i>) gene family. We identified 15 <i>GmIPT</i> genes in the soybean genome, which are unevenly distributed across 12 chromosomes; their evolutionary expansion is primarily driven by whole-genome duplication events. Phylogenetic analysis of soybean IPT proteins with those from Arabidopsis, rice and maize clustered them into four groups, exhibiting lineage-specific functional specialization. <i>GmIPT</i> genes exhibit significant variations in conserved motifs, gene structure, and cis-acting elements; their promoter regions are enriched in light-responsive, abiotic stress-responsive, and hormone-responsive elements, indicating their involvement in complex transcriptional regulatory networks. Tissue expression profiling revealed that <i>GmIPT7</i> and <i>GmIPT10</i> are highly expressed in various tissues, whereas <i>GmIPT14</i> shows specific expression in flowers and the shoot apical meristem. Transcriptomic analysis and qRT-PCR validation demonstrated that <i>GmIPT7</i>, <i>GmIPT10</i> and <i>GmIPT15</i> respond differentially to drought, salt and low-temperature stress, with <i>GmIPT15</i> exhibiting a transient upregulation at 3 h (<i>p</i> < 0.01) followed by a gradual decline to levels close to the pre-treatment control at 6-12 h under low-temperature stress. We further performed haplotype analysis of <i>GmIPT15</i> and identified a putative elite haplotype (hap1) associated with cold tolerance based on low-temperature germination index assessment. This study provides useful insights for the future functional characterization of plant IPT genes and offers potential genetic resources and molecular markers that may support molecular-assisted breeding for soybean abiotic stress tolerance.