25 research outputs found
Recommended from our members
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 (EpichloĂ« 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 someâincluding the infamous ergot alkaloidsâhave 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
Chronic coral consumption by butterflyfishes
Interactions between predators and prey organisms are of fundamental importance to ecological communities. While the ecological impact that grazing predators can have in terrestrial and temperate marine systems are well established, the importance of coral grazers on tropical reefs has rarely been considered. In this study we estimate the biomass of coral tissue consumed by four prominent species of corallivorous butterflyfishes. Sub-adult butterflyfishes (60-70mm, 6-11g) remove between 0.6 and 0.9g of live coral tissue per day, while larger adults (>110mm, ~40-50g) remove between 1.5 and 3g of coral tissue each day. These individual consumption rates correspond to the population of coral-feeding butterflyfishes at three exposed reef crest habitats at Lizard Island, Great Barrier Reef consuming between 14.6g (±2.0) and 19.6g (±3.9).200m-2.day-1 of coral tissue. When standardised to the biomass of butterflyfishes present, a combined reef wide removal rate of 4.2g (±1.2) of coral tissue is consumed per 200m-2.kg-1 of coral-feeding butterflyfishes. The quantity of coral tissue removed by these predators is considerably larger than previously expected and indicates that coral-grazers are likely to play an important role in the transfer of energy fixed by corals to higher consumers. Chronic coral consumption by butterflyfishes is expected to exact a large energetic cost upon prey corals and contribute to an increased rate of coral loss on reefs already threatened by anthropogenic pressure and ongoing climate change