Submitted to: Plant Breeding
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/5/2008
Publication Date: 11/19/2008
Publication URL: www3.interscience.wiley.com/cgi-bin/fulltext/121535855/PDFSTART
Citation: Luo, M., Liu, J., Lee, R.D., Guo, B.Z. 2008. Characterization of gene expression profiles in developing kernels of maize (Zea mays) inbred Tex6. Plant Breeding. 127:569-578. Interpretive Summary: By using maize microarray tchnology, our goal is to study gene expression profiles in maize developing kernels from 25 day after pollination (DAP). We are interested in understanding biochemical and metabolic pathways in the late developmental kernels, and understanding how metabolic pathways are regulated at the gene expression level in kernels of Tex6, a maize inbred line reported with reduced aflatoxin contamination. Because of the resistant traits of Tex6, this maize line would be an interesting candidate for studies of gene expression temporal patterns in developing kernels during the time favorable to aflatoxin contamination and for better understanding the resistance and identifying genes linked to the resistant traits. In this report, transcriptional profiles of Tex6 kernels at 25, 30, 35, 40, and 45 DAP were compared and quatitative real-time PCR was also used for validation of microarray studies. There was a total of 8621 positive array gene spots and 4247 cross-talking genes identified in all sampling stages. These were averaged at 6218 array spots expressed in each sampling stage. Expression patterns of key genes in several metabolic pathways were studied. Some defense related genes were highly expressed throughout the late kernel development. The real-time PCR reproduced the expression patterns of up- and down-regulated genes. Gene annotation provided a global overview of the molecular biological function of these genes differentially expressed during maize kernel development. The gene expression profiles in the late stages of Tex6 kernels before harvest may help us to understand the molecular mechanism of resistance in Tex6 and to explore some important target genes which could be used to develop resistant varieties in the future.
Technical Abstract: Maize oligonuleotide microarray was used to analyze the temporal patterns of gene expression in late developmental maize kernels 25 days after pollination (DAP). There was a total of 57,452 70-mer oligonucleotides on the array. We analyzed gene expression profiles in the developing kernels of Tex6, reported to have drought tolerance and reduced aflatoxin contamination, at 25, 30, 35, 40 and 45 DAP. There was a total of 8621 positive array spots with unique IDs and 4247 cross-talking genes identified in all sampling stages. These were averaged at 6218 array spots expressed in each sampling stage. Expression patterns of key genes in several metabolic pathways, including starch, lipid and storage proteins, were analyzed. Among the storage proteins, the expression patterns of defense related genes (2676 unique IDs) were identified as up-regulated, down-regulated, or no-change based on hierarchical analysis. Some defense related genes were highly expressed throughout the late kernel development. Twenty genes with different expression trends from microarray were selected for validation using quantitative real-time PCR. The real-time PCR reproduced the expression patterns of up- and down-regulated genes, but did not completely reproduce the genes without changes as in the microarray study. Gene ontology (GO) annotation provided a global overview of the molecular biological function of these genes differentially expressed during maize kernel development. This study was able to investigate the gene categories at various stages of kernel development, therefore providing further insight into the molecular importance of the gene expression associated with the reduction of aflatoxin contamination in Tex6.