Overexpression of a high-affinity phosphate transporter gene from tobacco (NtPT1) enhances phosphate uptake and accumulation in transgenic rice plants

High-affinity phosphate transporters (PTs) have been suggested as major components of mechanisms of inorganic phosphate (Pi) uptake in plant cells. In this study, we investigated the role of PT in improving Pi uptake by transgenic overexpression of a tobacco (Nicotiana tabacum L.) gene encoding a high-affinity PT (NtPT1) in rice (Oryza sativa L.) plants. The NtPT1 transgene driven by the maize ubiquitin (Ubi) promoter was expressed constitutively in transgenic rice plants at very high levels both in low (32 mu M Pi) and high (320 mu M Pi) Pi conditions. The rate of Pi uptake increased by 24% and 37% in the transgenic rice plants at low and high Pi conditions, respectively. Significant increases in phosphorus (P) accumulation (41% (w/w) and 55% (w/w)) were observed in the leaves of the transgenic plants under low and high Pi conditions, respectively. The P content in the shoots of the transgenic plants grown in low-P soil with Pi applied at 0-62 mg/Kg soil was increased by 15% (w/w) to 29% (w/w). The P content in seeds of the transgenic plants grown under field conditions was also increased by 16% (w/w) to 25% (w/w). The positive correlation between Pi uptake and accumulation and NtPT1 transgene expression indicates transcriptional control of PT activity and an important regulatory role of PT in Pi uptake. These results also confirm that high-affinity PTs are important targets for the improvement of Pi acquisition in rice.