Poster: Reproductive Development

Abs # 456: What roles do apple AFL1 and AFL2 genes, which are FLORICAULA/LEAFY orthologues, play in flowering?

Presenter:	Wada, Masato , mwada@affrc.go.jp
Authors	Wada, Masato  (A)   Kotoda, Nobuhiro  (A)   Bessho, Hideo  (A)
Affiliations:	(A): National Institute of Fruit Tree Science

The apple tree (Malus domestica) usually has a juvenile phase that lasts several years. The genetic factors controlling flower development in the apple tree are not yet clear. Recently, however, a number of@genes involved in flower formation of Arabidopsis have been reported. LEAFY from Arabidopsis and FLORICAULA from Antirrhinum majus are important elements of the transition from the vegetative to reproductive phases. Two orthologues of FLORICAULA/LEAFY, AFL1 and AFL2 (Apple FLO/LFY), have been isolated from apple tree flower buds. AFL1 and -2 showed high identity to each other (90%) and a high degree of similarity to PTLF and PEAFLO (70%), which are orthologues of FLO/LFY from poplar and pea, respectively. RNA blot analysis showed that AFL1 is expressed only in the floral bud during the transition from vegetative to reproductive growth, whereas AFL2 is expressed in the vegetative shoot apex, floral buds, floral organs and root. The transgenic Arabidopsis with overexpressed AFL2 showed accelerated flowering and gave rise to several solitary flowers from rosette axils directly. AFL1 had similar effects, but the phenotypes of the transgenic Arabidopsis were weaker with AFL1 than with AFL2. These results indicated that AFL1 and -2 were orthologues of FLO/LFY, and that the functions of AFL1 and -2 are close to each other. Genomic Southern analysis demonstrated that each cultivar has a variety of AFL genes. The apple cultivar eJonathanf, which was used as material, has another AFL homologue except for AFL1 and -2, the homologue very similar to AFL1, but@it has excess 1.2 kb fragment in the first intron. Therefore, we have discussed the functional differences between AFL1 and -2 in the apple tree.