ABSTRACT
Genomic research is revolutionizing plant biology. The recent completion of the Arabidopsis and rice genomes is a major milestone in plant science that is already yielding many exciting discoveries about genetic pathways, developmental networks, and genome evolution (1,2). This work, along with the completion of other eukaryotic genomes, clearly shows that there is no substitute for knowledge of complete genome sequence. For example, it is now clear that even with substantial investment, expressed sequence tag (EST) sequencing projects will probably not discover all of the genes in an organism. Many sequences are over-represented in cDNA libraries, and highly regulated genes may be absent or under-represented. As recently shown for chromosome 10 of rice, even draft sequencing may reveal only 50% of the genes that can be identified by complete sequencing of the chromosome (2). Phenotypic comparisons between phylogenetically close relatives (e.g., monkey and man; maize and teosinte) reveal that knowledge of gene regulation is critical to understanding genome function. This kind of information can come only from full genome sequencing. In addition, sequence information alone has limited utility unless fully integrated into the genetic and physical maps of the genome. Thus, mapping and sequencing are both essential elements for understanding the physical genomics of any organism.
