Genome-wide analysis of PHT gene family and their role in LP and salt stress in sweet potato

Phosphate transporters (PHTs), which are essential for phosphate (Pi) uptake, translocation, and utilization, play crucial roles in regulating plant growth and development. Despite extensive characterization of PHTs in many plant species, their function in sweet potato remains unclear. Here, we conducted a genome-wide investigation, and identified 27 PHTs in cultivated hexaploid sweet potato (Ipomoea batatas L.), which are divided into five clusters (IbPHT1-IbPHT5). Phylogenetic analysis and collinearity analysis showed that sweet potato shares a closer homological evolutionary relationship with dicotyledonous (Arabidopsis) species compared with the monocotyledonous (rice). Promoter analysis revealed that the MYB (myeloblastosis) cis-element is the most abundant among all cis-elements found in the promoters of IbPHTs. RNA-seq analysis in different tissues and under low phosphate (LP) stress revealed that IbPHT1;3, IbPHT1;4, IbPHT1;5 and IbPHT3;3 were the most highly expressed genes in sweet potato. IbPHT1; 5, which located on plasma membrane, was functionally characterized and involved in Pi uptake and transport in transgenic Arabidopsis and yeast. Besides, the Pi uptake and transcriptome analysis assay showed that salt stress inhibits Pi uptake and expression of most members in PHT1 subfamily (at least 50%). This suggested that PHTs may play crucial roles in salt stress response in sweet potato. This study provides new insights for understanding the function of IbPHTs, which are candidate for improving phosphorus use efficiency and abiotic stress tolerance in cultivated sweet potato.