OsNAC74 affects grain protein content and various biological traits by regulating OsAAP6 expression in rice

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.