Effect of the expression level of an AGAMOUS-like gene on the petaloidy of stamens in the double-flowered lily, 'Elodie'

Double-flowered lilies, in which stamens are converted to petaloid organs, are valuable for horticulturists. 'Elodie' is a double-flowered lily cultivar in which stamens are homeotically converted into petaloid organs in whorl 3. The 'Elodie' cultivar shows individual variation in stamen structure and it was therefore classified into the following three types according to the strength of petaloidy of the stamens: weak (type-I), intermediate (type-II), and strong (type-III) phenotypes. The AGAMOUS (AG) gene is a class C floral identity gene in Arabidopsis thaliana that is involved in the formation of stamens and carpels. An AG-like gene was isolated from 'Elodie' (LelAG1) and its expression was compared between flower types. The LelAG1 gene was expressed in whorls 3 and 4, but not in whorls 1 and 2 in all flower types. In type-I flowers, LelAG1 was expressed strongly in whorls 3 and 4, while its expression was significantly decreased in whorl 3 in type-III flowers. In type-II intermediate phenotype flowers, the expression level of LelAG1 in whorl 3 was reduced by 60%. These results suggest that the expression level of AG-like genes is correlated with the degree of petaloidy of the stamens.