Overexpression of MdMADS5, an APETALA1-like gene of apple, causes early flowering in transgenic Arabidopsis

An apple ( Malus× domestica) gene MdMADS5, a putative homolog of Arabidopsis APETALA1 ( AP1) and Antirrhinum SQUAMOSA, was introduced into Arabidopsis using Agrobacterium tumefaciens EHA101 to examine how the gene affects flowering and whether it may be effective in producing transgenic apple that flowers early. Five of the 15 primarily transformed ( T 1) plants flowered 5–10 days earlier than wild-type plants and produced only two to three rosette leaves when they flowered. The terminal flowers on the transgenic plants resembled transgenic Arabidopsis expressing 35S:: AP1 or tfl1 mutant plants. This phenotype observed in T 1 transgenic plants was inherited in the following generation. Based on these results, it was suggested that the function of the MdMADS5 gene was similar to that of the AP1 gene. Although the mechanism of flower-bud formation in the apple might be different from that in Arabidopsis, the MdMADS5 gene might be involved in flower-bud formation of the apple.