Format: ORAL

Luis Miguel Prieto1, Aura Urrea Trujillo1, Carolina Rodrguez-Pelayo2, Natalia Pabn Mora1

1 Universidad de Antioquia, Instituto de Biologia, Medellin, Colombia 2. Instituto de Biología Celular y Molecular de Plantas, Universidad Politecnica de Valencia, Valencia, España.  

Ferns constitute the second most diverse lineage of vascular plants on Earth, surpassed only by angiosperms. In most recent phylogenies, ferns appear monophyletic. In both ferns and lycophytes, gametophytes and sporophytes can grow independently as multicellular haploid and diploid bodies, respectively. Gametes are generated through cellular differentiation in the haploid gametophyte, which by itself a product of spore germination. After fertilization, the zygote develops into a new sporophyte. In comparison to angiosperms, few developmental studies have focused on ferns, and the studies made have emphasized morphological diversity and gene expression data in the sporophytic phase. For instance, several studies have addressed the expression of identity and leaf development genes, as well as reproductive transition genes in fronds and during sporangia formation. Similar analyses are lacking in the haploid phase: the gametophyte. This study standardized spore germination and gametophyte growth in Adiantum raddianum and Anemia villosa. Morphological changes and developmental timing were documented for all haploid stages, from spore germination to zygote formation. Successful optimization of RNA extractions from tiny individuals allowed expression analyses for LEAFY (LFY) and Phosphatidylethanolamine Binding Protein (PEBP) genes. These gene lineages control the reproductive transition in angiosperms, and are hypothesized to play similar roles in ferns, due to their wide expression in fern sporophytes, especially in sporangia throughout their maturation. Our data shows active expression of LFY and PEBP homologs in fern gametophytes. We will discuss the specific expression patterns and their putative functions in spore germination, gametophyte growth, or the formation of antheridia and archegonia and gametogenesis in early-diverging vascular plants.