Systematic Identification of Phosphate Transporter Family 1 (PHT1) Genes and Their Expression Profiling in Response to Low Phosphorus and Related Hormones in Fagopyrum tataricum (L.) Gaertn.

Accumulating evidence suggests that the plasma membrane-localized phosphate transporter 1 (PHT1) family plays a fundamental role in the absorption, translocation, and re-mobilization of phosphorus in plants. Buckwheat (Fagopyrum spp.) exhibits high efficiency in phosphate uptake and wide adaptability to grow in under-fertilized soils. Despite their physiological importance, a systematic analysis of PHT1 genes in buckwheat has not been conducted yet. In this study, we performed a genome-wide identification and expression profile of the PHT1 gene family in Tartary buckwheat (Fagopyrum tataricum Gaertn). A total of eleven putative PHT1 genes (FtPHT1;1 to 1;11) were identified with an uneven distribution on all the F. tataricum chromosomes except for chromosomes 2, 3, and 5. All the FtPHT1s share the conserved domain GGDYPLSATIxSE, a typical signature of PHT1 transporters. A phylogenetic analysis indicated that FtPHT1 proteins could be clustered into four distinct subgroups, well supported by the exon–intron structure, consensus motifs, and the domain architecture. A gene duplication analysis suggested that tandem duplication may largely contribute to the expansion of the FtPHT1 gene family members. In silico predictions of cis-acting elements revealed that low-phosphate-responsive elements, such as W-box, P1BS, and MBS, were enriched in the promoter regions of FtPHT1 genes. Quantitative real-time PCR assays showed differential but partially overlapping expression patterns of some FtPHT1 genes in various organs under limited Pi supply and hormone stimuli, implying that these FtPHT1 transporters may be essential for Pi uptake, translocation, and re-mobilization, possibly through signaling cross-talk between the low phosphate and hormones. These observations provide molecular insights into the FtPHT1 gene family, which paves the way to a functional analysis of FtPHT1 members in the future.