The improved phosphorus utilization and reduced phosphorus consumption of ppk-expressing transgenic rice

To reduce the phosphorus (P) environmental resources consume, it is imperative to cultivate new elite rice varieties with a higher utilization efficiency of P fertilizer. The expression of the polyphosphate kinase gene (ppk) can mediate the synthesis of polyphosphate by free inorganic phosphate (Pi), and mimicking the Pi deficiency signal in plants, thereby enhancing plant Pi uptake of Pi by plants. A ppk from Microcystis aeruginosa had been expressed in Nipponbare, and the ppk-expressing transgenic rice (ETR) had been successfully constructed. In this research, two field experiments were carried out from 2018 to 2019 using different P fertilizer (superphosphate) treatments with high P (HP, 450 kg/ha), medium P (MP, 225 kg/ha), low P (LP, 112.5 kg/ha) and no P (NP, 0 kg/ ha) at test sites in Changxing County in the Yangtze Delta and in Sanya, an island city in southeastern China's Hainan province. Unlike the increase in grain yield of wild type Nipponbare (WT), coincident with the increase in P fertilizer, the grain yield of ETR with a single-copy line (ETRS) reached the maximum in MP treatment in Changxing and in LP treatment in Sanya. More importantly, when P fertilizer was insufficient, the grain yield of ETRS was significantly higher than WT. Correlation analysis showed that the increase in ETRS production can be the result of more tillers. At the same time, a quantitative Real-Time PCR (qRT-PCR) was performed and the results revealed altered expressions of some key genes involved in the P metabolism and ETRS. As a result, changes in genes expressions increased the number of tillers and thus improved grain yield when the P fertilizer was inadequate. Our study provided a strategy for constructing a high P utilization rice, which will make a strong contribution toward reducing P fertilizer use in rice production in China.