Identification and expression analysis of the Hevea brasiliensis phosphate transporter 1 gene family

Twelve HbPHT1s were identified in Hevea and most of them were induced by phosphate starvation. HbPHT1;5 complemented the defective yeast mutant strain EY917 and HbPHT1;7 only partly complemented it. Phosphorus is an important element of the latex of rubber tree, and its content affects the quality and yield of latex. However, with the outflow of latex, a large amount of phosphorus is lost. The phosphate transporter 1 (PHT1) family proteins regulate the phosphorus acquisition and translocation in the plants, but their expression and roles in Hevea brasiliensis remain unclear. In this work, we identified twelve HbPHT1s (HbPHT1;1 to HbPHT1;12). Evolutionary analyses suggested two duplication events: HbPHT1;5/HbPHT1;6 and HbPHT1;7/HbPHT1;8. In the promoter region of some HbPHT1s, there existed P1BS, W-box, MYB, and ethylene response cis-elements. All the HbPHT1s, except for HbPHT1;4, were expressed in the roots, and most of them were also expressed in the stems and leaves. HbPHT1;7 had the highest expression level in the roots, stems, and leaves. HbPHT1;5 and HbPHT1;6 had a relatively higher expression levels than other genes in latex. HbPHT1;5, HbPHT1;7, and HbPHT1;11 were induced by ethylene treatment. Most HbPHT1s were induced under phosphate starvation conditions in the seedling leaves, and the expression of HbPHT1;9 was 20-fold higher than the control. HbPHT1;5 complemented the deficiency of the yeast mutant strain EY917 in phosphate transportation under low- and high-phosphate conditions, and HbPHT1;7 restored the deficiency when 10 mM phosphate was supplied. These results suggested that the increased expression of PHT1s may improve the phosphate uptake, transport, and utilization in Hevea. It also provides the basis to sudy the phosphorus metabolism network and mine the gene resources for the genetic breeding of Hevea.