The grain protein content is an important quality trait in cereals, and the expression level of the OsAAP6 can significantly affect the grain protein content in rice. Through site-directed mutagenesis, we found that the position from −7 to −12 bp upstream of the transcription start site of the OsAAP6 was the functional variation site. By using the yeast single hybrid test, point-to-point in yeast, and the local surface plasmon resonance test, the OsNAC74 was screened and verified to be a regulator upstream of OsAAP6. The OsNAC74 is a constitutively expressed gene whose product is located on the cell membrane. The OsAAP6 and the genes related to the seed storage in the Osnac74 mutants were downregulated, and grain protein content was significantly reduced. In addition, OsNAC74 had a significant impact on quality traits such as grain chalkiness and gel consistency in rice. Although the Osnac74 mutant seeds were relatively small, the individual plant yield was not decreased. Therefore, OsNAC74 is an important regulatory factor with multiple biological functions. This study provides important information for the later use of OsNAC74 gene for molecular design and breeding in rice.

籽粒蛋白质含量是谷物的重要品质性状，OsAAP6的表达水平可显着影响水稻籽粒蛋白质含量。通过定点突变，我们发现OsAAP6转录起始位点上游-7至-12 bp的位置是功能变异位点。通过酵母单杂交试验、酵母中点对点试验以及局部表面等离振子共振试验，筛选并验证了OsNAC74是OsAAP6的上游调节因子。OsNAC74是一种组成型表达的基因，其产物位于细胞膜上。Osnac74突变体中OsAAP6和与种子贮藏相关的基因下调，籽粒蛋白质含量显着降低。此外，OsNAC74对稻谷的垩白度和凝胶稠度等品质性状具有显着影响。尽管Osnac74突变体种子相对较小，但单株产量并未降低。因此，OsNAC74是一种具有多种生物学功能的重要调控因子。本研究为后续利用OsNAC74基因进行水稻分子设计和育种提供重要信息。