OsPht1;8, a phosphate transporter, is involved in auxin and phosphate starvation response in rice

The responses of plants to auxin and phosphate (Pi) starvation are closely linked. However, the underlying mechanisms connecting the Pi starvation (-Pi) responses to auxin are largely unclear. Here, we show that OsPht1;8 (OsPT8), a phosphate transporter, functions in both the auxin and -Pi responses in rice (Oryza sativa L.) and tobacco (Nicotiana tabacum). The overexpression of OsPT8 (OsPT8-Oe) led to the loss of sensitivity to auxin and -Pi in adventitious roots, lateral roots, and root hairs in rice. The expression levels of OsPT8 and pOsPT8::GUS staining in roots, root-shoot junctions and leaves of rice were induced by IAA treatments. The number of young lateral roots in the OsPT8-Oe transgenic rice, which had higher auxin concentrations, was distinctly more than that in the wild-type, possibly as a result of increased expression of auxin-related genes under normal Pi condition. Moreover, tobacco overexpressing OsPT8 had a similar root phenotype to OsPT8-Oe rice. These data reveal a novel biological function of OsPT8 in the cross-talk between Pi and auxin signaling, and provide new evidence for the linkage between auxin and -Pi responses.