Elevated expression of OsAAP3in transgenic plants resulted in significantly higher amino acid concentrations of Lys, Arg, His, Asp, Ala, Gln, Gly, Thr and Tyr, and inhibited bud outgrowth and rice tillering. However, RNAi of OsAAP3 decreased significantly Arg, Lys, Asp and Thr concentrations to a small extent, and thus promoted bud outgrowth, increased significantly tiller numbers and effective panicle numbers per plant, and further enhanced significantly grain yield and nitrogen use efficiency (NUE). The promoter sequences of OsAAP3 showed some divergence between Japonica and Indica rice, and expression of the gene was higher in Japonica, which produced fewer tillers than Indica. We generated knockout lines of OsAAP3 on Japonica ZH11 and KY131 using CRISPR technology and found that grain yield could be increased significantly. These results suggest that manipulation of OsAAP3expression could be used to increase grain yield in rice.
Figure 1: The promoter sequence of OsAAP3 has SNP divergence between rice Japonica and Indica, and its expression level is associated with rice tiller. (a) SNP divergence in the promoter sequence of OsAAP3. (b) The phylogeny of promoter sequence of OsAAP3. (c) The expression level of OsAAP3 in different tissues in ZH11. (d) The root, basal part, leaf sheath, young leaf, old leaf, young panicle and old panicle GUS staining using pOsAAP3::GUS transgenic plant. (e) The average expression level of OsAAP3 in the culm of rice Japonica and Indica in a diverse worldwide collection of 524 O. sativa landraces (Chen et al., 2014). (f) Tiller number in ten cultivars Japonica and ten cultivars Indica. (g) The expression of OsAAP3 in the culm of ten cultivars Japonica and ten cultivars Indica.