Generation of OsNAR2.1 Transgenic Rice

The OsNAR2.1 overexpression transgenic line (Ov199) used in this study, which was named as pUbi-OsNAR2.1, have been described in detailed in previous studies (Chi et al., 2011 (link); Chen et al., 2017 (link)). Briefly, we amplified the OsNAR2.1 ORF sequence from cDNA isolated from the Oryza sativa L. ssp. Japonica and ligated it into the expression vector containing the Ubi promoter. The expression construct was later transferred into Agrobacterium tumefaciens strain EHA105 by electro-poration, followed by transformation into the rice as described by Upadhyaya et al. (Fan et al., 2020 (link)). A previously described procedure was adopted to generate the OsNAR2.1 RNAi line (RNAi) (Yan et al., 2011 (link)).