Identification of the first fungal annexin: Analysis of annexin gene duplications and implications for eukaryotic evolution

Annexin homologues have been found in animals, plants, and distinct protist lineages. We report the identification of the first fungal annexin, encoded by the anxI4 gene of the filamentous ascomycete Neurospora crassa. Annexins have a complex evolutionary history and exhibit a large number of gene duplications and gene losses in various taxa, including the complete loss of annexin sequences from another ascomycete, the budding yeast Saccharomyces cerevisiae. Surprisingly, the N. crassa annexin homologue is most closely related to the annexin homologue of the slime mold Dictyostelium discoideum, suggesting a phylogenetic link between cellular slime molds and true fungi. Both of these annexin homologues are closely related to the family of annexin homologues present in animals, an observation consistent with the existence of the animal-fungal clade. These data further suggest that the gene duplications that generated the family of annexin sequences present in animals, fungi, and slime molds began prior to the divergence of these taxa.