The nuclear encoded glycerol-3-phosphate acyltransferase gene (GPAT) has been found to be single copy in a number of angiosperm families. In this study we investigated the phylogenetic utility of the GPAT gene in determining the interspecific relationships of the angiosperm genus Paeonia. An approximately 2.3 kb fragment of the GPAT gene was amplified, cloned, and sequenced from all diploid and selected tetraploid species of Paeonia. The GPAT gene may exist as a single copy in some species of Paeonia, but constitutes a small gene family in others. Two distinct genomic clones of P. anomala containing the GPAT gene have been characterized and suggest that the gene underwent an ancient duplication followed by the formation of a pseudogene in one copy. Blast sequence similarity analysis suggests that the GPAT pseudogene may contain a large retrotransposon-like insertion that could have triggered the pseudogene formation. The rate of evolution of the GPAT gene was determined to be greater than that of the nuclear ITS region in Paeonia, demonstrating the potential of the GPAT gene to be used in resolving low-level taxonomic relationships of angiosperms. When compared to existing gene phylogenies, such as the cpDNA matK gene, nuclear ITS region and the alcohol dehydrogenase genes, the GPAT gene phylogeny yielded additional insights into the relationships within Paeonia.

Key words: nuclear gene GPAT, Paeonia, Paeoniaceae