Conservation of gene structure and activity in the regulation of reproductive organ development of conifers and angiosperms

The Norway spruce (Picea abies) gene DAL2 shows distinct structural similarities to angiosperm MADS-box genes which act in the control of the development of the sexual organs of the flower. Transcription of DAL2 is restricted to the reproductive organs, the unisexual cones, of Norway spruce. In this paper we show that DAL2 in the compound female cone is exclusively expressed in the developing ovule-bearing organ, the ovuliferous scale. When expressed constitutively in transgenic Arabidopsis the gene causes developmental alterations very similar to those observed in plants ectopically expressing the Arabidopsis gene AGAMOUS and the closely related Brassica napus gene BAG1. These alterations include homeotic transformations of floral organs. On the basis of these data and analysis of the phylogeny of the plant MADS-box gene family, we propose that DAL2 acts to control reproductive organ development in spruce. We also propose that DAL2 shares a common origin with AGAMOUS and related genes from other angiosperms, in an ancestral MADS-box gene that was active in the control of ontogeny of ovule-bearing organs in the unknown last common ancestor of conifers and angiosperms.