Impact of environmental and genetic factors on expression of maize gene classes: Relevance to grain composition

Regulatory proteins, such as transcription factors, have markedly influenced plant phenotype during crop domestication, and breeding and modifying their expression through modern biotechnology may prove valuable in the development of improved agricultural traits. Crops improved through biotechnology-derived traits are subject to comparisons of chemical and nutrient composition with that of conventional crops prior to commercialisation. These comparisons are typically framed in the context of natural variation of analyte components. This study reports on an evaluation of natural variation in maize (Zea mays L.) gene expression based on a survey of 2200 genes in order to better understand heterogeneity in levels of transcription factor gene expression under a range of genomic and environmental conditions. This evaluation was conducted on leaf tissue collected from hybrids of 48 genetically diverse inbred lines each crossed with one of two tester inbred lines and grown at three different field sites in Iowa, USA. The data show that expression of transcription factor genes in the overall population was highly variable across this range of genomic and environmental factors, though no more so than expression of other gene functional classes, despite the profound influence transcription factors have exerted on plant phenotype during crop domestication and breeding. By comparison, levels of grain components (oil, protein, total amino acid and fatty acid levels) were generally consistent with values recorded in the literature. Thus, the results highlight that heterogeneity of gene expression in response to diverse genomic and environmental factors is not unique to genes for transcription factors and that such variation in gene expression does not correlate with differences in grain composition.