The Rice Phosphate Transporter Protein OsPT8 Regulates Disease Resistance and Plant Growth

The absorption of nutrients and disease resistance are two indispensable physiological processes in plants; however, it is still largely unknown whether there is cross-talk between their molecular signaling pathways. In this study, we identified the rice OsPT8 protein, which is a member of the phosphate transporters (PTs) Pht1 family and also plays a role in rice disease resistance. The transcriptional level of OsPT8 is suppressed after infection with rice pathogens and treatment with pathogen-associated molecular patterns (PAMPs). Overexpression of OsPT8 suppresses rice disease resistance against the pathogens Magnaporthe oryzae and Xanthomonas oryzae pv. oryzae . Accordingly, the transcription level of resistance related genes, such as PAL and PBZ1 , is inhibited in plants overexpressing OsPT8 ( OsPT8- OX) after inoculation with these pathogens. In OsPT8-OX plants, PAMPs-triggered immunity (PTI) response genes, such as OsRac1 and SGT1 , are suppressed during treatment with PAMPs chitin or flg22. Moreover, the typical response of PTI is suppressed after chitin or flg22 treatment. We also identified OsPT8 as an interactor of a rice mitogen-activated protein kinase BWMK1, which is a regulator of disease resistance. Under low phosphate (Pi) conditions, the OsPT8- OX plants display better agronomic traits than the control plants. However, the differences in development between OsPT8- OX and the control plants are reduced upon the increase of Pi concentration. These results demonstrate that OsPT8 regulates the transduction of Pi signaling for development and negatively regulates rice immunity.