Genome-wide analysis of AHP genes in soybean and the role of GmAHP10 in improving salt stress tolerance.

The histidine phosphotransfer proteins (AHP) plays a pivotal role in the cytokinin signal transduction pathway, which is vital for plant growth, development, and resistance to biotic and abiotic stresses. Despite its importance, the AHP genes in soybean (Glycine max (L.) Merr.) have not been characterized until now. In this study, we utilized bioinformatics analysis, transcriptome sequencing, and qRT-PCR to explore the AHP gene family in soybean. We identified 17 AHP gene members unevenly distributed across nine chromosomes, with all AHP proteins classified into four types based on their motifs and gene structures. Phylogenetic analysis and conserved protein motifs revealed strong homology and conservation between soybean and Arabidopsis AHP family members. Collinearity analysis suggested that segmental duplication events were the primary mechanism for the expansion of the soybean AHP family. Tissue-specific expression analysis indicated that most AHP family genes were highly expressed in soybean roots. Transcript profiles and qRT-PCR data demonstrated that many GmAHP genes were significantly up-regulated in response to salt stress, particularly GmAHP10. Overexpression of GmAHP10 in soybean hairy roots significantly promoted root system development and enhanced salt tolerance. Further physiological analyses revealed that overexpression of GmAHP10 significantly reduced H₂O₂ and malondialdehyde (MDA) levels by increasing the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), as well as elevating proline concentration compared to controls. These findings provide a foundation for understanding the biological roles of GmAHP genes in soybean growth, development, and response to salt stress.