Plant, Animal & Microbe Genomes X Conference Plant, Animal & Microbe Genomes X ConferenceJanuary 12-16, 2002
Town & Country Convention Center
San Diego, CA
Workshop: Databases, Gene Systematics, and Nomenclature
Evidence suggests that multiple genome duplications may have occurred in the legume Glycine max. We sought to examine soybean genome structure and the evolutionary and/or functional significance of the structure using an EST-based approach. Randomly chosen EST sequences were used to generate groups of related ESTs. These groups were sorted into subsets of unique transcripts. Most groups represented single transcripts (43%); however, groups containing two (29%) or four (13%) members were also prevalent, supporting the hypothesis of multiple gene duplication events. We further examined 144 groups containing just two isoforms. Differences between isoform pairs occurred mainly as small gaps or as synonymous mutations (62%), and approximately fifty percent of non-synonymous mutations did not change amino acid charge or polarity. This suggests that, to a large extent, the protein products of duplicated isoforms have retained their sequence similarity and could imply that the isoforms are functionally redundant. To address the functional significance of gene duplication, we identified fifteen members of a polygalacturonase-related gene family from the Genbank soybean EST collection. The genes were found to occur as unique transcripts as well as closely related isoform pairs and quartets. For some pairs, expression patterns across the soybean EST libraries differed significantly from one another. Other pairs, perhaps arising from more recent gene duplications, retained both sequence and expression similarity. Further analysis is necessary to determine whether tissue-specific expression underlies functional divergence. These types of analyses can be extended to comparative multispecies studies. Potential pitfalls associated with these comparisons will be discussed.