RNA-Seq Revealed the Molecular Mechanism of Nutritional Quality Improvement in <i>o16-wx</i> Double-Mutation Maize

The enhancement of the nutritional composition of maize grains could be achieved by the introduction of a mutation with a heightened lysine content. To obtain double-recessive mutant lines for the <i>o16</i> and <i>wx</i> genes, a molecular-marker-assisted selection technique was used to backcross them into conventional maize lines. The resultant maize was subsequently utilized to explore the molecular mechanism responsible for the maize’s nutritional quality. Based on this, an RNA-seq investigation was conducted using the employing kernels during the development period of maize kernel (18, 28, and 38 DAP) to examine the gene expression involved in amino metabolism. The results revealed that a total of 27 and 34 differentially expressed genes (DEGs) were identified in tryptophan metabolism and lysine metabolism, respectively, across three time periods. In the lysine synthesis pathway, the genes encoding AK, ASD, and DapF were found to be up-regulated at various stages, encouraging lysine synthesis. Conversely, in the lysine degradation pathway, the genes encoding ALDH7A1 and LKR/SDH were down-regulated, suggesting an increase in lysine content. In the process of tryptophan metabolism, the down-regulation of genes encoding TAA and ALDH led to an increase in tryptophan content. In addition, the down-regulation of genes encoding α-zein resulted in a decrease in zein content, thereby enhancing the nutritional quality of maize. These findings hold substantial significance for elucidating the transcriptional-level molecular mechanism, underlying the accumulation of <i>o16</i> and <i>wx</i> genes to improve maize grain quality, as well as offering valuable insight for the development of biomarkers and gene editing.