Plant-symbiotic fungi as chemical engineers: multi-genome analysis of the Clavicipitaceae reveals dynamics of alkaloid Loci

The fungal family Clavicipitaceae includes plant symbionts and parasites that produce several psychoactive and bioprotective alkaloids. The family includes grass symbionts in the epichloae clade (Epichloë and Neotyphodium species), which are extraordinarily diverse both in their host interactions and in their alkaloid profiles. Epichloae produce alkaloids of four distinct classes, all of which deter insects, and some—including the infamous ergot alkaloids—have potent effects on mammals. The exceptional chemotypic diversity of the epichloae may relate to their broad range of host interactions, whereby some are pathogenic and contagious, others are mutualistic and vertically transmitted (seed-borne), and still others vary in pathogenic or mutualistic behavior. We profiled the alkaloids and sequenced the genomes of 10 epichloae, three ergot fungi (Claviceps species), a morning-glory symbiont (Periglandula ipomoeae), and a bamboo pathogen (Aciculosporium take), and compared the gene clusters for four classes of alkaloids. Results indicated a strong tendency for alkaloid loci to have conserved cores that specify the skeleton structures and peripheral genes that determine chemical variations that are known to affect their pharmacological specificities. Generally, gene locations in cluster peripheries positioned them near to transposon-derived, AT-rich repeat blocks, which were probably involved in gene losses, duplications, and neofunctionalizations. The alkaloid loci in the epichloae had unusual structures riddled with large, complex, and dynamic repeat blocks. This feature was not reflective of overall differences in repeat contents in the genomes, nor was it characteristic of most other specialized metabolism loci. The organization and dynamics of alkaloid loci and abundant repeat blocks in the epichloae suggested that these fungi are under selection for alkaloid diversification. We suggest that such selection is related to the variable life histories of the epichloae, their protective roles as symbionts, and their associations with the highly speciose and ecologically diverse cool-season grasses

Beneficial effects of Neotyphodium tembladerae and Neotyphodium pampeanum on a wild forage grass

Asexual, vertically transmitted fungal endophytes of the genus Neotyphodium are considered to enhance growth, stress resistance and competitiveness of agronomic grasses, but have been suggested to have neutral or deleterious effects on wild grasses. We studied whether the associations between Bromus auleticus and their endophytes, Neotyphodium pampeanum and Neotyphodium tembladerae, are beneficial for this wild forage grass native to South America. In a greenhouse experiment, 3‐month‐old endophyte‐infected plants (E+) showed enhanced growth relative to their endophyte‐free counterparts (E−). In a one‐year‐long experiment in the field, E+ plants showed higher survival and regrowth rate, and produced more biomass and seeds than E− plants. Only with respect to the seed output did N. tembladerae seem to be detrimental, whereas N. pampeanum did not affect this parameter. No differences were observed with respect to the germination of seeds produced by E+ or E− plants. Loline alkaloids were detected in N. pampeanum‐infected plants. Our results show that, similar to results with agronomic grasses, in wild grasses, the symbiosis with Neotyphodium species could be mutualistic.EEA Concepción del UruguayFil: Iannone, Leopoldo Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Micología y Botánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Micología y Botánica; ArgentinaFil: Pinget, Albertina Daniela. Universidad de Concepción del Uruguay. Facultad de Ciencias Agrarias; ArgentinaFil: Nagabhyru, P. University of Kentucky. Department of Plant Pathology; Estados UnidosFil: Schardl, Christopher L. University of Kentucky. Department of Plant Pathology; Estados UnidosFil: De Battista, Jose Pedro. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Concepción del Uruguay; Argentin

Cross-species transcriptomics identifies core regulatory changes differentiating the asymptomatic asexual and virulent sexual life cycles of grass-symbiotic <i>Epichloë</i> fungi

AbstractFungi from the genus EpichloëEpichloëEpichloëEpichloëEpichloëEpichlo