Abstract
In maize, opaque2 (o2) and opaque16 (o16) alleles can increase lysine content, while the waxy (wx) gene can enhance the amylopectin content of grains. In our study, o2 and o16 alleles were backcrossed into waxy maize line (wxwx). The o2o2o16o16wxwx lines had amylopectin contents similar to those of waxy line. Their nutritional value was better than waxy line, but the mechanism by which the o2 and o16 alleles increased the lysine content of waxy maize remained unclear. The o2o2o16o16wxwx lines and their parents on kernels (18th day after pollination) were subjected to RNA sequencing (RNA-Seq). The RNA-Seq analysis revealed 272 differentially expressed genes (DEGs). Functional analyses revealed that these DEGs were mainly related to biomass metabolism. Among them, in o2o2o16o16wxwx lines, 15 genes encoding α-zein were down-regulated, which resulted in the reduction of α-zein synthesis and increased lysine content; lkr/sdh1 and Zm00001d020984.1 genes involved in the lysine degradation pathway were down-regulated, thereby inhibited lysine degradation; sh2, bt2 and ae1 genes involved in starch metabolism were upregulated, leaded to wrinkling kernel and farinaceous endosperm. Our transcriptional-level identification of key genes responsible for increased grain lysine content and farinaceous endosperm formation following introgression of o2 and o16 alleles should promote molecular breeding for maize quality.
Highlights
Despite the above improvements, high-lysine maize with a single gene mutation cannot meet the nutritional quality needs of food and food processing nor the lysine content requirements of livestock and poultry feed[29]
The increased level of lysine in o2o2o16o16wxwx lines largely depends on the reduction of α-zein synthesis which excludes lysine, while several non-zein proteins which accounts for most of the higher percentage of lysine are associated with varying degrees of increased accumulation[49]
Compared with the wxwx parent, in the o2o2o16o16wxwx lines, 15 genes encoding α-zein were down-regulated, which resulted in the reduction of α-zein synthesis and correspondingly in the increasement of non-zein, thereby increased lysine content
Summary
High-lysine maize with a single gene mutation cannot meet the nutritional quality needs of food and food processing nor the lysine content requirements of livestock and poultry feed[29]. The pyramiding of high-lysine mutant genes can increase lysine and tryptophan contents to improve the nutritional quality of maize grains. To boost the lysine content of waxy maize, Zhang et al.[35] used MAS to generate 18 inbred quality-protein maize lines containing wx and o2 alleles These lines had lysine contents of 0.36–0.54%, which was 1.15–27.06% higher than those of the original parents. Using MABB, Zhang et al.[38] introgressed o2 and o16 alleles into wxwx lines and obtained three waxy maize lines containing o2 and o16 alleles, the mean grain lysine content was 0.62%, and the waxy property was equal to that of the recurrent parents, meeting the food and feed requirements of humans, livestock and poultry. To identify the molecular mechanism underlying the increased lysine content of waxy maize following introgression of o2 and o16 alleles, we carried out a transcriptome analysis of kernels on 18th day after pollination (18DAP) to examine transcriptional expression differences between o2o2o16o16wxwx mutants and their recurrent parent
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
