The expression of two DEFICIENS-like genes was reduced in the sepaloid tepals of viridiflora tulips

According to the modified ABC model, class B genes are expressed in whorl 1 as well as in whorls 2 and 3, therefore the organs of whorls 1 and 2 have the same petaloid structure in many monocots. The viridiflora tulip, a well-known cultivar group, has flowers in which the tepals in whorls 1 and 2 have greenish stripes. This phenotype could be expected as class B mutant by the modified ABC model. In this study, we discovered that tepal phenotypes correlated with that of stamens. We isolated two class A genes (TGSQA and TGSQB) from wild type tulip. Northern hybridization of these two class A genes, and the class B genes (TGDEFA, TGDEFB and TGGLO), showed that the expression of TGDEFA and TGDEFB in the viridiflora tulips were weaker than those in wild type cultivars, whereas the expression patterns of the rest genes were almost identical. From our results, we suggest that reduced expression of the two DEF-like genes, TGDEFA and TGDEFB, is involved in the development of the viridiflora phenotype. This reduced expression could be caused by the amino acid difference.