Characterization of FPF1-homologous genes in maize --Pokutta, L, Brettschneider, R, Wienand, U After flower induction, the Flowering Promoting Factor 1 (FPF1)-gene (Kania, T et al., Plant Cell 9:1327-1338, 1997) is one of the earliest expressed genes in Sinapis alba and Arabidopsis thaliana plants. FPF1 is expressed in the peripheral zone of the apical meristems immediately after the photoperiodic induction of flowering. Later in development, it can also be found in floral meristems and in axillary meristems that form the secondary inflorescences. The FPF1 gene encodes a 12.6 kD protein that has no homology to any protein with a known function. There are indications that FPF1 is involved in the gibberellin-dependent pathway and modulates the gibberellin response in apical meristems during the transition to flowering. Overexpression of the FPF1 gene in transgenic Arabidopsis thaliana plants led to shortening of the vegetative phase and earlier flowering of these plants (Kania, T et al., Plant Cell 9:1327-1338, 1997).

The cloning of maize genes homologous to the FPF1 of Sinapsis alba revealed the existence of a FPF gene family in maize consisting of at least 9 members. Three of them were used for a genomic and expression analysis. The results of the Northern experiments show that one of the genes, ZmFPF(L), is exclusively expressed in immature cobs and immature tassel, whereas ZmFPF(B) is predominantly expressed in leaves. No expression could be detected for the third gene, ZmFPF(E), although this gene shows a very high homology to ZmFPF(B) in the coding region. These results indicate that individual FPF genes of Zea mays are expressed in different tissues and may have different functions.

A search of genomic and EST-databases for FPF-homologue sequences indicates that this gene family is ubiquitous to the plant kingdom, including the moss Physcomytrella patens, gymnosperms, and di- and monocotyledon angiosperms. A dendrogram, analysing the relationship of 28 different putative FPF-genes, shows that the sequences are clustered in three mayor subgroups. In the second group, only sequences of monocotyledonous plant species are clustered (see Figure 1).

Figure 1. Comparison of FPF-sequences. At: Arabidopsis thaliana, Gm: Glycine max, Hv: Hordeum vulgare, Lj: Lotus japonicus, Le: Lycopersicon esculentum, Mc: Mesembryanthemum crystallinum, Mt: Medicago truncatula, Nt: Nicotiana tabacum, Os: Oryza sativa, Pp: Physcomitrella patens, Sa: Sinapis alba, Tt: Triticum turgidum, Zm: Zea mays.

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