Assessing Novel Genes Associated Wtih Starch Content in Maize through Transcript Profiling Analysis

Presently there is increased interest in studying and improving crops for production of bio-fuels. Improving starch concentration in maize (Zea mays L.) would likely be a great asset for the ethanol industry. From the cross of the high starch maize line Illinois Low Protein cycle 90 (ILP) × B73 backcrossed to B73, 150 S1, 138 S3, and 138 S3 testcross lines were developed. Transcript profiling analysis was employed to assess differences in gene expression between selected high and low starch S1 families and testcross progenies. Two time points, 15 and 20 days after pollination (DAP), were evaluated. A model was implemented to identify overall differentially expressed genes in the two populations. In addition, the contrast of the 15 vs. 20 DAP was used to identify genes that increased or decreased relative expression during seed development. A total of 89 genes with consistent expression patterns across time points and populations were selected. None of the genes evaluated were found significant in the 15 vs. 20 DAP contrast indicating no major changes in gene expression between high and low families occur between the two time points. Only two known starch biosynthesis related genes were identified. One, alpha amylase inhibitor (AAI), showed the highest fold difference in expression among all genes represented on the chip. Further expression differential of this gene was evaluated in RT-PCR which strengthened the hypothesis of the gene being related to final starch concentration present in materials derived from ILP×B73. Our results strongly support a likely function of AAI gene in final starch accumulated in ILP×B73 derived materials. In order for higher starch concentration materials to serve as useful donors to commercial hybrids, they should provide reasonably competitive grain yields. Thus in the oral presentation we provide information on yield trial performance of testcross hybrids of ILP/B73 derived materials in relation to commercial checks and experimental hybrids derived from PVP released materials. *Present Address: 7963 Paseo Aliso, Carlsbad, CA 92009