Developmentally regulated expression of two MADS-box genes, MdMADS3 and MdMADS4, in the morphogenesis of flower buds and fruits in apple

Two MADS-box genes, MdMADS3 and MdMADS4, (Malus x domestica Borkh.) cultiva r Fuji, and their spatial and temporal expression patterns were studied dur ing morphological differentiation of the flower buds and the fruits. Both M dMADS3 and MdMADS4 showed high sequence similarities to FBP2 from petunia, TM5 from tomato, and AGL2, AGL4 from Arabidopsis. Although MdMADS3 was expr essed in the inner three whorls of the floral primordium, its expression wa s hardly detectable in developing fruit. The second gene, MdMADS4, was ubiq uitously expressed in the inflorescence meristem, floral meristem, all four floral organs, and fruit. Moreover, MdMADS4 expression was high in the vas cular bundles assigned to the floral tube and the carpellary vascular bundl es in fruit at early developmental stages. The MdMADS4 transcript also accu mulated in embryos of the developing seeds. These results suggest that MdMA DS3 and MdMADS4 are involved in different functions, and that MdMADS4 may f unction in the important events controlling flower and fruit development. M ADS-box genes, MdMADS3 were isolated from the apple and fruit development.