Abstract
Improving sulfur assimilation in maize kernels is essential due to humans and animals’ inability to synthesize methionine. Serine acetyltransferase (SAT) is a critical enzyme that controls cystine biosynthesis in plants. In this study, all SAT gene members were genome-wide characterized by using a sequence homology search. The RNA-seq quantification indicates that they are highly expressed in leaves, other than root and seeds, consistent with their biological functions in sulfur assimilation. With the recently released 25 genomes of nested association mapping (NAM) founders representing the diverse maize stock, we had the opportunity to investigate the SAT genetic variation comprehensively. The abundant transposon insertions into SAT genes indicate their driving power in terms of gene structure and genome evolution. We found that the transposon insertion into exons could change SAT gene transcription, whereas there was no significant correlation between transposable element (TE) insertion into introns and their gene expression, indicating that other regulatory elements such as promoters could also be involved. Understanding the SAT gene structure, gene expression and genetic variation involved in natural selection and species adaption could precisely guide genetic engineering to manipulate sulfur assimilation in maize and to improve nutritional quality.
Highlights
Maize is one of the most important crops in terms of its high yield and broadly derived commodities
A total of four Serine acetyltransferase (SAT) gene family members were characterized in the B73 genome by homology searches
We found that the SAT genes were more highly expressed in leaves than in the seed and root tissues (Figure 3), consistent with their function in Cys and Met biosynthesis in leaves, where SAT is a committing enzyme for sulfur assimilation
Summary
Maize is one of the most important crops in terms of its high yield and broadly derived commodities. The exploration of genetic variation and expression patterns for the SAT gene family would provide sufficient genetic resources and superior alleles to further manipulate maize’s sulfur content. The 25 nested association mapping (NAM) parental lines (B97, CML52, CML69, CML103, CML228, CML247, CML277, CML322, CML333, HP301, Il14H, Ki3, Ki11, Ky21, M37W, M162W, Mo18W, Ms71, NC350, NC358, Oh7B, Oh43, P39, Tx303 and Tzi8) representing diverse maize lines in modern breeding [14] were selected for sequencing and deciphering maize genetic diversity [15] They became a set of essential resources for the maize community to answer critical questions about how structural variations determine the phenotypic traits and adaption to the different environments. The further molecular genetic analysis of SATs involving gene expression and transposon insertion paves the way to precisely manipulate sulfur assimilation in maize
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