Exploring the Genetic Landscape of Histidine Phosphotransfer Proteins in the Oryza Genus

Histidine phosphotransfer proteins (HP/Hpts) are key components in the two-component system (TCS) involved in cytokinin signalling. In rice, five Hpt genes have been identified, including two authentic and three pseudo-Hpts. This study focused on isolating and characterizing the OsHpt4/PHP2-like gene from three O. indica rice varieties, and on exploring the evolutionary and regulatory features of the Hpt gene family across Oryza species. Hence, we isolated the OsHpt4/PHP2-like gene (456 bp; 151 amino acids) from three O. indica rice varieties- ASD-16 (Parentage- ADT 31/Co39), ADT-54 (Parentage-I.W.Ponni/ Banskathi) and CO-52 (Parentage- BPT 5204/ Co (R) 50) and compared their physicochemical properties. To gain broader insights, a genome-wide analysis was conducted across six Oryza species (Oryza sativa ssp. japonica, Oryza sativa ssp. indica, Oryza rufipogon, Oryza nivara, Oryza glumaepatula, and Oryza barthii), identifying 35 Hpt isoforms. Studies on gene structure and conserved motifs showed that intron and exon organization, as well as motif composition, are well preserved. Phylogenetic analysis grouped Hpts into four main clusters with other monocots. Both segmental and tandem gene duplications contributed to gene family expansion. Promoter analysis revealed cis-elements responsive to phytohormones, abiotic stresses, light, and development. These results offer new insights into the evolution and regulation of Hpt genes in rice, and it paves a strong avenue for future research on stress tolerance and crop improvement.