The G protein γ subunit is important for nitrogen uptake and grain yield in rice under elevated CO2

Aims The gene qPE9-1, which encodes the G protein gamma subunit, is important for nitrogen (N) use in rice and in regulating rice photosynthesis under elevated CO2 (eCO(2)). However, under a changing climate, the qPE9-1 response to combined increasing atmospheric CO2 (aCO(2)) and soil N availability is unclear. Therefore, we investigated the regulative roles of qPE9-1 in rice N use under eCO(2). Methods Wild-type (WT) and qPE9-1 RNAi rice plants were exposed to low (LN) and high (HN) N treatments under aCO(2) (400 ppm) and eCO(2) (800 ppm) in the growth chamber and the field Open-Top Chamber (OTC). Rice growth, net photosynthetic rate, and N uptake were determined in the growth chamber. Then, the OTC was used to evaluate to the combined impacts of eCO(2) and N on rice yield. Results Under HN conditions, the dry weight and net photosynthesis rate of WT plants was significantly increased under eCO(2) compared with aCO(2); however, there was no significant difference in the qPE9-1 RNAi lines. The CO2 and N levels had relatively minor effects on the carbon concentration of all plants. Regardless of the CO2 concentration, the N concentrations in the roots and leaves of all plants were significantly reduced under LN treatment compared with HN. Under LN conditions, eCO(2) enhanced the N content of WT plants, but had no significant effects on the RNAi lines. The grain yield of WT plants was also significantly increased by eCO(2) under HN treatment in the field OTC, whereas the RNAi lines were not affected. Conclusion The G protein gamma subunit qPE9-1 is involved in N uptake under elevated CO2; however, this response is affected by N levels. These findings provide useful information on efficient N management for adapting to the future CO2-enriched environment.