Phylogenetic footprints in fern spore- and seed-specific gene promoters.

Spermatophyte seed-storage proteins have descended from a group of proteins involved in cellular desiccation/hydration processes. Conserved protein structures are found across all plant phyla and in the fungi and Archaea. We investigated whether conservation in the coding region sequence is paralleled by common gene regulatory processes. Seed- and spore-specific gene promoters of three phylogenetically diverse plants were analysed by transient and transgenic expression in Arabidopsis thaliana and tobacco. The transcription factors FUS3 and ABI3, which are central regulators of seed maturation processes, interact with cis-motifs of seed-specific promoters from distantly related plants. The promoter of a fern spore-specific gene encoding a seed-storage globulin-like protein exhibits strong seed-specific activity in both Arabidopsis and tobacco. The existence of phylogenetic footprints indicates good conservation of regulatory pathways controlling gene expression in fern spores and in gymnosperm and angiosperm seeds, reflecting the concerted evolution of coding and regulatory regions.