Characterization of a multigene family encoding an exopolygalacturonase in maize

Genes coding for exopolygalacturonase in plants are abundantly expressed during the development of the male gametophyte (pollen). We have analysed genomic and cDNA clones for several representatives of the small multigene family encoding exopolygalacturonase from Zea mays. Structures for both actively transcribed genes and non-transcribed pseudogenes are reported. Comparisons of the nucleotide sequences for coding and flanking regions of different members of the gene family reveal surprisingly few base substitutions, suggesting that the exopolygalacturonase gene family of maize arose through very recent multiple duplication events. The pseudogenes are shown to possess an 80 bp insertion within the coding region, which may represent a relictual intron that has been lost in the active genes. We estimate that 12 exopolygalacturonase genes exist in maize. None appear to be expressed at a detectable level in tissue other than those associated with pollen development.