Biology subjects

Stajich, J. E.

Publications and source records attributed to Stajich, J. E..

3 recordsLinked to original sources

bioRxiv2018

Comparative genomics and divergence time estimation of the anaerobic fungi in herbivorous mammals

The anaerobic gut fungi (AGF) or Neocallimastigomycota inhabit the rumen and alimentary tract of herbivorous mammals, where they play an important role in the degradation of plant fiber. Comparative genomic and phylogenomic analysis of the AGF has long been hampered by their fastidious growth pattern as well as their large and AT-biased genomes. We sequenced 21 AGF transcriptomes and combined them with 5 available genome sequences of AGF taxa to explore their evolutionary relationships, time their divergence, and characterize patterns of gene gain/loss associated with their evolution. We estimate that the most recent common ancestor of the AGF diverged 66 ({+/-}10) million years ago, a timeframe that coincides with the evolution of grasses (Poaceae), as well as the mammalian transition from insectivory to herbivory. The concordance of these independently estimated ages of AGF evolution, grasses evolution, and mammalian transition to herbivory suggest that AGF have been important in shaping the success of mammalian herbivory transition by improving the efficiency of energy acquisition from recalcitrant plant materials. Comparative genomics identified multiple lineage-specific genes and protein domains in the AGF, two of which were acquired from an animal host (galectin) and rumen gut bacteria (carbohydrate-binding domain) via horizontal gene transfer (HGT). Four of the bacterial derived "Cthe_2159" genes in AGF genomes also encode eukaryotic Pfam domains ("Atrophin-1", "eIF-3_zeta", "Nop14", and "TPH") indicating possible gene fusion events after the acquisition of "Cthe_2159" domain. A third AGF domain, plant-like polysaccharide lyase N-terminal domain ("Rhamnogal_lyase"), represents the first report from fungi that potentially aids AGF to degrade pectin. Analysis of genomic and transcriptomic sequences confirmed the presence and expression of these lineage-specific genes in nearly all AGF clades supporting the hypothesis that these laterally acquired and novel genes in fungi are likely functional. These genetic elements may contribute to the exceptional abilities of AGF to degrade plant biomass and enable metabolism of the rumen microbes and animal hosts.

evolutionary biology↗

bioRxiv2018

Discovery of psychoactive plant and mushroom alkaloids in ancient fungal cicada pathogens

Entomopathogenic fungi routinely kill their hosts before releasing infectious spores, but select species keep insects alive while sporulating, which enhances dispersal. Transcriptomics and metabolomics studies of entomopathogens with post-mortem dissemination from their parasitized hosts have unraveled infection processes and host responses, yet mechanisms underlying active spore transmission by Entomophthoralean fungi in living insects remain elusive. Here we report the discovery, through metabolomics, of the plant-associated amphetamine, cathinone, in four Massospora cicadina-infected periodical cicada populations, and the mushroom-associated tryptamine, psilocybin, in annual cicadas infected with Massospora platypediae or Massospora levispora, which appear to represent a single fungal species. The absence of some fungal enzymes necessary for cathinone and psilocybin biosynthesis along with the inability to detect intermediate metabolites or gene orthologs are consistent with possibly novel biosynthesis pathways in Massospora. The neurogenic activities of these compounds suggest the extended phenotype of Massospora that modifies cicada behavior to maximize dissemination is chemically-induced.

ecology↗

bioRxiv2018

Early diverging insect pathogenic fungi of the order Entomophthorales possess diverse and unique subtilisin-like serine proteases

Insect-pathogenic fungi use subtilisin-like serine proteases (SLSPs) to degrade chitin-associated proteins in the insect procuticle. Most insect-pathogenic fungi in the order Hypocreales (Ascomycota) are generalist species with a broad host-range, and most species possess a high number of SLSPs. The other major clade of insect-pathogenic fungi is part of the subphylum Entomophthoromycotina (Zoopagomycota, formerly Zygomycota) which consists of high host-specificity insect-pathogenic fungi that naturally only infect a single or very few host species. The extent to which insect-pathogenic fungi in the order Entomophthorales rely on SLSPs is unknown. Here we take advantage of recently available transcriptomic and genomic datasets from four genera within Entomophthoromycotina: the saprobic or opportunistic pathogens Basidiobolus meristosporus, Conidiobolus coronatus, C. thromboides, C. incongruus, and the host-specific insect pathogens Entomphthora muscae and Pandora formicae, specific pathogens of house flies (Muscae domestica) and wood ants (Formica polyctena), respectively. We use phylogenetics and protein domain analysis to show that the obligate biotrophic fungi E. muscae, P. formicae and the saprobic human pathogen C. incongruus all contain \"classical\" fungal SLSPs and a unique group of SLSPs that loosely resembles bacillopeptidase F-like SLSPs. This novel group of SLSPs is found in the genomes of obligate insect pathogens and a generalist saprobic opportunistic pathogen why they are unlikely to be responsible for the host specificity of Entomophthorales. However, this class represent a unique group of SLSPs so far only observed among Bacteria, Oomycetes and early diverging fungi such as Cryptomycota, Microsporidia, and Entomophthoromycotina and missing in the sister fungal lineages of Kickxellomycotina or the fungal phyla Mucoromyocta, Ascomycota and Basidiomycota fungi suggesting interesting gene loss patterns.

evolutionary biology↗