Characterization of an AGAMOUS gene expressed throughout development of the fleshy fruit-like structure produced by XXXX around its seeds.

@entity4044 @entity523
BACKGROUND: The involvement of MADS-box genes of the AGAMOUS lineage in the formation of both flowers and fruits has been studied in detail in Angiosperms. AGAMOUS genes are expressed also in the reproductive structures of Gymnosperms, yet the demonstration of their role has been problematic because Gymnosperms are woody plants difficult to manipulate for physiological and genetic studies. Recently, it was shown that in the gymnosperm @entity4044 an AGAMOUS gene was expressed throughout development and ripening of the fleshy fruit-like structures produced by this species around its seeds. Such fleshy structures are evolutionarily very important because they favor the dispersal of seeds through endozoochory. In this work a characterization of the @entity4044 gene was carried out by over-expressing it in @entity523 . RESULTS: In @entity523 plants ectopically expressing the @entity4044 AGAMOUS gene a macroscopic anomaly was observed only in the flower sepals. While the wild type sepals had a leaf-like appearance, the transgenic ones appeared connately adjoined at their proximal extremity and, concomitant with the development and ripening of the fruit, they became thicker and acquired a yellowish-orange color, thus indicating that they had undergone a homeotic transformation into carpel-like structures. Molecular analyses of several genes associated with either the control of ripening or the ripening syndrome in @entity523 fruits confirmed that the transgenic sepals behaved like ectopic fruits that could undergo some ripening, although the red color typical of the ripe @entity523 fruit was never achieved. CONCLUSIONS: The ectopic expression of the @entity4044 AGAMOUS gene in @entity523 caused the homeotic transformation of the transgenic sepals into carpel-like structures, and this showed that the gymnosperm gene has a genuine C function. In parallel with the ripening of fruits the related transgenic sepals became fleshy fruit-like structures that also underwent some ripening and such a result indicates that this C function gene might be involved, together with other gens, also in the development of the @entity4044 fruit-like structures. It seems thus strengthened the hypothesis that AGAMOUS MADS-box genes were recruited already in Gymnosperms for the development of the fleshy fruit habit which is evolutionarily so important for the dispersal of seeds.
