With continued improvements in molecular genetic technologies, it has now become feasible to undertake projects with the aim of isolating and identifying most, if not all, of the expressed genes within an organism, as is currently underway in the Human Genome Project. In one strategy, often referred to as the "EST approach" and pioneered by Craig Venter and associates (Adams et al., Nature Supp. 377:3-174, 1995), large numbers of cDNA clones are prepared, sequenced (usually by a single-pass from the presumed 5' end of the mRNA), and then categorized based upon their identification by sequence similarity to known gene sequences from within GenBank and other databases. With the high rate of evolutionary conservation at the amino acid level, it has proven practical to identify up to 35% of these clones by sequence similarity to another gene with a previously studied function, often crossing species and even phyla boundaries to detect these functional relationships. In fact one of the greatest impacts of these types of projects may be the ability to "access" the results of biological studies in any other species by finding a "homolog" in your own species of choice through sequence similarity detected at the amino acid level with other better studied entries in the public databases. Given the abilities to produce large and representative cDNA libraries, to efficiently sequence hundreds of thousands of such clones, and to identify many clones by similarity analyses, such projects are capable of isolating and identifying tens of thousands of cloned genes with putative functions. Initial studies in corn on a relatively small scale (Keith et al., Plant Physiol. 101:329-332, 1993; Shen et al., Plant Mol. Biol. 26:1085-1101, 1994) have already amply demonstrated the utility of this approach by providing plant researchers with maize homologs for many important genes.
Consequently, given the power of this general approach to significantly increase our general knowledge of genes and their functions, Pioneer Hi-Bred has decided to undertake a large-scale corn EST program in conjunction with Human Genome Sciences (HGS). Pioneer researchers will endeavor to produce gene-enriched libraries which will be submitted to HGS for single-pass sequencing from the presumed 5' terminus of the original mRNA. We plan to explore the use of standard, high complexity cDNA libraries prepared from a variety of tissues and treatments, normalized libraries, subtracted libraries, and other innovative approaches, all in an effort to identify as many genes as possible. By comparison with other sequences already in the public databases, we then hope to identify many of these genes to some putative functions. In line with this general goal, we are also exploring additional research strategies to establish both the genetic map locations and expression patterns of these clones, as well as to deploy our technology for mutational analyses of many of these genes (Meeley and Briggs, MNL 69:67&82, 1995).
Pioneer is currently developing plans which will provide opportunities for collaborative research in this area with researchers in the public sector. The EST information will provide for many new investigations in a variety of areas of plant biology. Once the details are finalized on the organization of these potential collaborations, they will be communicated to the maize research community. Pioneer welcomes this continued opportunity to work with the maize research community with the goals of both meeting Pioneer's product development objectives and advancing the state of knowledge of maize genetics.
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