Abstract
The opaque2 (o2) mutation in maize is associated with high lysine content in endosperm and good nutritional value. To improve the nutritional quality of waxy maize, the o2 allele was introgressed into the wxwx line using marker-assisted backcrossing selection technology. The lysine content of o2o2wxwx lines was higher than that of the wxwx line. To reveal the mechanism of increasing lysine content through introgression of the o2 in waxy maize, the transcriptome on kernels (18th day after pollination) of the o2o2wxwx and parent lines was analyzed using RNA-sequencing (RNA-Seq). The RNA-Seq analysis revealed 49 differentially expressed genes (DEGs). Functional analysis showed that these DEGs were mostly related to the catalytic activity and metabolic processes. The O2 gene regulated multiple metabolic pathways related to biological processes (BP) and molecular function (MP) during waxy maize endosperm development. In particular, in the o2o2wxwx lines, the two genes that encode the EF-1α and LHT1 were up-regulated, but the gene that encodes sulfur-rich proteins was down-regulated, raising the grain lysine content. These findings are of great importance for understanding the molecular mechanism underlying the lysine content increase due to o2 allele introgression into waxy maize.
Highlights
Corn (Zea mays L.) is one of the main fodder and food crops
The results showed that grain seeds of the recurrent parent and o2o2wxwx mutant were smooth, opaque, and waxy (Figure 1A,B)
Gene ontology (GO) functional classification was performed for 49 significantly different genes; the results shown in Figure 5 and Table S7 were related to cell components (CC), molecular function (MF), and biological processes (BP)
Summary
Corn (Zea mays L.) is one of the main fodder and food crops. The quality and taste of corn can directly affect healthy development in humans, livestock, and poultry. Lysine is an essential amino acid for monogastric animals such as humans, livestock, and poultry, and the amylopectin content in starch is closely related to food quality. The Waxy (Wx) gene is located on the long arm of chromosome 9, and encodes granule-bound starch synthase I (GBSS-I). It determines the amylose synthesis in maize endosperm and pollen [9,10,11,12,13]. The mutated endosperm was caused by genetic drift and its lysine content was not high enough (0.24–0.34%) to meet the nutritional quality requirements for human consumption and food processing [14]
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