Mannans (possibly galacto- or galactogluco-mannans) are present in tomato endosperm cell walls. Three enzymes participate in the complete depolymerization of galactomannan: [alpha]-galactosidase (EC 3.2.1.22), endo-[beta]-mannanase (EC 3.2.1.78), and [beta]-mannosidase (EC 3.2.1.25). The activity of each enzyme in tomato seeds has its own distinct program of regulation and no co-ordination of activity is seen. [alpha]-Galactosidase and [beta]-mannoside mannohydrolase activities are also present in tomato fruit pericarp and also show different patterns of activity. A cDNA encoding an [alpha]-galactosidase has been isolated from a germinated tomato seed cDNA library and shows significant homology with known dicotyledonous [alpha]-galactosidase cDNAs. [alpha]-Galactosidase gene expression is relatively constant throughout germination with a slight increase after germination. A southern hybridization analysis reveals that there is only one gene for [alpha]-galactosidase in the tomato (cv. Trust).