Expression of Floral Specific Genes in Tomato Hypocotyls in Liquid Culture

Cytological and histological analysis of hypocotyl expiants of many species revealed the occurrence of meiotic-like events (somatic meiosis and prophase reduction) located into structures differentiated around the vascular strands. These structures could be assimilated to primitive reproductive organs (pistil- and anther-like) containing pollen-like and embryo-sac like cells. Previous work demonstrated that segregating events in carrot are a prerequisite for the acquisition of totipotency Here the floral nature of the structures developed from hypocotyls in culture was demonstrated, at the molecular level, in expiants of tomato, Lycopersicon being a specie where floral specific genes are available. In situ hybridization experiments showed, in tomato hypocotyls cultured in vitro, the induction of two tomato floral specific genes: the TM8, a gene of the MAD family which in vivo is highly expressed specifically in floral meristems, and the MON 9612, a floral specific gene very tightly spatially and temporally regulated in tomato pistils. A study of the temporal pattern expression of these genes was performed by RT-PCR