OsNAR2.1 induced endogenous nitrogen concentration variation affects transcriptional expression of miRNAs in rice

The studies of rice nitrogen concentration on the expression of miRNA so far are mostly limited to the exogenous nitrogen, leaving the effect of endogenous nitrogen largely unexplored. OsNAR2.1 is a high-affinity nitrate transporter partner protein which plays a central role in nitrate absorption and translocation in rice. The expression of OsNAR2.1 could influence the concentration of the endogenous nitrogen in rice. We showed that the expression and production of miRNA in rice can be influenced by manipulating the endogenous nitrogen concentration via OsNAR2.1 transgenic lines. The small RNA content, particularly 24 nucleotides small RNA, expressed differently in two transgenic rice lines (nitrogen efficient line with overexpression of OsNAR2.1 (Ov199), nitrogen-inefficient line with knockdown OsNAR2.1 by RNAi (RNAi)) compared to the wild-type (NP). Comparative hierarchical clustering expression pattern analysis revealed that the expression profiles of mature miRNA in both transgenic lines were different from NP. Several previously unidentified miRNAs were identified to be differentially expressed under different nitrogen concentrations, namely miR1874, miR5150, chr3-36147, chr4-27017 and chr5-21745. In conclusion, our findings suggest that the level of endogenous nitrogen concentration variation by overexpression or knockdown OsNAR2.1 could mediate the expression pattern and intensity of miRNA in rice, which is of high potential to be used in molecular breeding to improve the rice responses towards nitrogen utilization

Effects of Carbon and Nitrogen Fertilisers on Rice Quality of the OsNRT2.3b-Overexpressing Line

Excessive nitrogen fertiliser use reduces nitrogen use efficiency and causes significant damage to the environment. Carbon fertilisers have the advantage of improving soil fertility; however, the effects of carbon and nitrogen fertilisers on rice yield and quality are not clear. In this study, the nitrogen-efficient line (OsNRT2.3b-overexpressing [O8]) and wild type (WT) were treated with different levels of nitrogen and carbon fertilisers under field conditions to study the effects of different fertilisation treatments on rice quality. The results showed that the appearance, nutrition, and taste qualities of O8 were generally high compared with WT under various fertilisation treatment conditions in 2019 and 2020. Compared with 90 kg/ha and 270 kg/ha nitrogen fertiliser, a single application of 90 kg/ha and 270 kg/ha carbon fertiliser significantly reduced the protein content of O8 by approximately 37.08% and 35.50% in 2019 and 2020, respectively, compared with WT, and improved the eating quality of O8 and WT. However, the replacement of nitrogen fertiliser with 20% carbon fertiliser did not improve the eating quality of O8 and WT compared with a single application of nitrogen fertiliser. This study identifies a high-quality gene, OsNRT2.3b, for breeding high-quality rice and provides a theoretical basis for obtaining high-quality rice and molecular breeding

Effects of Carbon and Nitrogen Fertilisers on Rice Quality of the <i>OsNRT2.3b</i>-Overexpressing Line

Excessive nitrogen fertiliser use reduces nitrogen use efficiency and causes significant damage to the environment. Carbon fertilisers have the advantage of improving soil fertility; however, the effects of carbon and nitrogen fertilisers on rice yield and quality are not clear. In this study, the nitrogen-efficient line (OsNRT2.3b-overexpressing [O8]) and wild type (WT) were treated with different levels of nitrogen and carbon fertilisers under field conditions to study the effects of different fertilisation treatments on rice quality. The results showed that the appearance, nutrition, and taste qualities of O8 were generally high compared with WT under various fertilisation treatment conditions in 2019 and 2020. Compared with 90 kg/ha and 270 kg/ha nitrogen fertiliser, a single application of 90 kg/ha and 270 kg/ha carbon fertiliser significantly reduced the protein content of O8 by approximately 37.08% and 35.50% in 2019 and 2020, respectively, compared with WT, and improved the eating quality of O8 and WT. However, the replacement of nitrogen fertiliser with 20% carbon fertiliser did not improve the eating quality of O8 and WT compared with a single application of nitrogen fertiliser. This study identifies a high-quality gene, OsNRT2.3b, for breeding high-quality rice and provides a theoretical basis for obtaining high-quality rice and molecular breeding