Isolation and characterization of floral organ identity genes from Asparagus officinalis L.

In higher dicotyledonous plants, the floral organs are arranged in four different whorls, containing sepals, petals, stamens and carpels. The specification of floral organ identity is explained by the ABC model. By this model, the combination of B- and C-function genes specifies stamen formation in whorl 3, and expression of the C-function gene alone results in the formation of carpels in whorl 4. In this study, we performed RACE cloning to isolate cDNA clones of B- and C-function genes from Asparagus officinalis L. Since these genes specify male and female reproductive organs, they are very useful for modification of sex expression in asparagus by overexpressing or suppressing the expression of these genes. B-function is contributed by two different genes, DEFICIENS(DEF)-like and GLOBOSA(GLO)-like genes, and C-function is provided by one gene, AGAMOUS(AG)-like gene. We have isolated one cDNA clone of DEF-like gene, two of GLO-like gene and two of AG-like genes from asparagus. We have named the respective genes AODEF, AOGLOA and AOGLOB, AOAG1 and AOAG2, respectively. Southern hybridization showed that there were 1-2 copies of AODEF and AOGLOA genes, and several copies of AOAG1 genes in asparagus genome. Northern blot analysis showed that these genes were specifically expressed in flower buds and not in vegetative tissues.