The golden decade of molecular floral development (1990-1999): A cheerful obituary

Floral meristem identity genes are expressed during tendril development in grapevine

To study the early steps of flower initiation and development in grapevine (Vitis vinifera), we have isolated two MADS-box genes, VFUL-L and VAP1, the putative FUL-like and AP1 grapevine orthologs, and analyzed their expression patterns during vegetative and reproductive development. Both genes are expressed in lateral meristems that, in grapevine, can give rise to either inflorescences or tendrils. They are also coexpressed in inflorescence and flower meristems. During flower development, VFUL-L transcripts are restricted to the central part of young flower meristems and, later, to the prospective carpel-forming region, which is consistent with a role of this gene in floral transition and carpel and fruit development. Expression pattern of VAP1 suggests that it may play a role in flowering transition and flower development. However, its lack of expression in sepal primordia, does not support its role as an A-function gene in grapevine. Neither VFUL-L nor VAP1 expression was detected in vegetative organs such as leaves or roots. In contrast, they are expressed throughout tendril development. Transcription of both genes in tendrils of very young plants that have not undergone flowering transition indicates that this expression is independent of the flowering process. These unique expression patterns of genes typically involved in reproductive development have implications on our understanding of flower induction and initiation in grapevine, on the origin of grapevine tendrils and on the functional roles of AP1-and FUL-like genes in plant development. These results also provide molecular support to the hypothesis that Vitis tendrils are modified reproductive organs adapted to climb.

Ancestral MADS box genes in Sugi, Cryptomeria japonica D. Don (Taxodiaceae), homologous to the B function genes in angiosperms

In flowering plants, flower organ identity is controlled by the ABC genes, including several MADS box genes. We present two MADS box genes of a conifer, Cryptomeria japonica D. Don. The genes, CjMADS1 and CjMADS2, were related to the angiosperm B function genes which determine the identities of petals and stamens. A phylogenetic analysis showed that these genes form a new clade outside the angiosperm B group, that is, PISTILLATA (PI) and APETALA3 (AP3) lineages. CjMADS1 had a PI-group specific motif and CjMADS2 had AP3-group specific motifs at the C terminal end, respectively. CjMADS1 was expressed in male strobili (or cones) throughout its development, while CjMADS2 was transiently expressed during male strobilus development. The specific expression in the male reproductive organ indicated that the B function is maintained in gymnosperms. Our cladistic analysis suggests that the gene duplication event which generated B function gene lineages predates the divergence of angiosperms and gymnosperms and that the gene duplication which produced the two genes of C. japonica occurred in an ancestral conifer species.