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Genetic and biochemical differences in populations bred for extremes in maize grain methionine concentration
BMC Plant Biology
  • Mark A Newell, The Samuel Roberts Noble Foundation
  • Karla E Vogel, Iowa State University
  • Marie Adams, Iowa State University
  • Nevzat Aydin, Karamanoglu Mehmetbey University
  • Anastasia L Bodnar, Iowa State University
  • Muhammad Ali, North West Frontier Province Agricultural University
  • Adrienne N Moran Lauter, United States Department of Agriculture
  • M Paul Scott, United States Department of Agriculture
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Background Methionine is an important nutrient in animal feed and several approaches have been developed to increase methionine concentration in maize (Zea mays L.) grain. One approach is through traditional breeding using recurrent selection. Using divergent selection, genetically related populations with extreme differences in grain methionine content were produced. In order to better understand the molecular mechanisms controlling grain methionine content, we examined seed proteins, transcript levels of candidate genes, and genotypes of these populations. Results Two populations were selected for high or low methionine concentration for eight generations and 40 and 56% differences between the high and low populations in grain methionine concentration were observed. Mean values between the high and low methionine populations differed by greater than 1.5 standard deviations in some cycles of selection. Other amino acids and total protein concentration exhibited much smaller changes. In an effort to understand the molecular mechanisms that contribute to these differences, we compared transcript levels of candidate genes encoding high methionine seed storage proteins involved in sulfur assimilation or methionine biosynthesis. In combination, we also explored the genetic mechanisms at the SNP level through implementation of an association analysis. Significant differences in methionine-rich seed storage protein genes were observed in comparisons of high and low methionine populations, while transcripts of seed storage proteins lacking high levels of methionine were unchanged. Seed storage protein levels were consistent with transcript levels. Two genes involved in sulfur assimilation, Cys2 and CgS1 showed substantial differences in allele frequencies when two selected populations were compared to the starting populations. Major genes identified across cycles of selection by a high-stringency association analysis included dzs18, wx, dzs10, and zp27. Conclusions We hypothesize that transcriptional changes alter sink strength by altering the levels of methionine-rich seed storage proteins. To meet the altered need for sulfur, a cysteine-rich seed storage protein is altered while sulfur assimilation and methionine biosynthesis throughput is changed by selection for certain alleles of Cys2 and CgS1.

This article is published as Newell, Mark A., Karla E. Vogel, Marie Adams, Nevzat Aydin, Anastasia L. Bodnar, Muhammad Ali, Adrienne N. Moran Lauter, and M. Paul Scott. "Genetic and biochemical differences in populations bred for extremes in maize grain methionine concentration." BMC plant biology 14, no. 1 (2014): 49, doi: 10.1186/1471-2229-14-49.

Works produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted.
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Mark A Newell, Karla E Vogel, Marie Adams, Nevzat Aydin, et al.. "Genetic and biochemical differences in populations bred for extremes in maize grain methionine concentration" BMC Plant Biology Vol. 14 (2014) p. 49
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