Genomes of plant-associated clavicipitaceae

Fungi of family Clavicipitaceae serve as models for evolution on the symbiotic continuum from pathogenic to mutualistic. Clavicipitaceous fungi associate with plants, invertebrates, and other fungi. Most plant-associated Clavicipitaceae systemically colonize shoots, but the fungal fruiting structures are localized to inflorescences, florets, buds, leaves, or nodes. Many Clavicipitaceae decrease or eliminate host seed production, but some have evolved such intimate symbioses with plant hosts that they disseminate clonally in seeds (vertical transmission) without damage or any reduction in plant fertility. In such cases, the fungi dramatically enhance host fitness by producing defensive alkaloids and through other mechanisms. To date, sequences have been assembled for 26 Clavicipitaceae representing 21 species in seven genera. These include three Claviceps species that fruit on and replace host ovaries, two Metarhizium species that parasitize insects and associate with plant roots, and 21 strains of systemic plant parasites or symbionts. Of the latter, 14 are capable of vertical transmission, and of those, 7 are strictly seed-borne mutualists in genera Epichloë and Periglandula. Alkaloid biosynthetic genes are widely distributed among these fungi. Gene clusters for ergot alkaloids and indole-diterpenes, both of which are neurotoxins in vertebrates and invertebrates, are present in members of all seven genera. The genes for anti-insect loline alkaloids and peramine have a more restricted distribution, but are present in many of the vertically transmissible Epichloë species. The availability of these genome sequences will facilitate studies of the evolution and mechanisms underlying the diversity of metabolism, host interactions, and niche adaptation of plant-associated Clavicipitaceae.