Photosensing Fungi: Phytochrome in the Spotlight

Red light triggers asexual development and represses sexual development in the fungus Aspergillus nidulans. This response has been shown to require a phytochrome red/far-red light photoreceptor, FphA, which is cytoplasmic and binds a tetrapyrrole chromophore. FphA exhibits similarities to both plant and bacterial phytochromes

Ferrochelatase is a conserved downstream target of the blue light-sensing White collar complex in fungi

Light is a universal signal perceived by organisms, including fungi, in which light regulates common and unique biological processes depending on the species. Previous research has established that conserved proteins, originally called White collar 1 and 2 from the ascomycete Neurospora crassa, regulate UV/blue light sensing. Homologous proteins function in distant relatives of N. crassa, including the basidiomycetes and zygomycetes, which diverged as long as a billion years ago. Here we conducted microarray experiments on the basidiomycete fungus Cryptococcus neoformans to identify light-regulated genes. Surprisingly, only a single gene was induced by light above the commonly used twofold threshold. This gene, HEM15, is predicted to encode a ferrochelatase that catalyses the final step in haem biosynthesis from highly photoreactive porphyrins. The C. neoformans gene complements a Saccharomyces cerevisiae hem15Δ strain and is essential for viability, and the Hem15 protein localizes to mitochondria, three lines of evidence that the gene encodes ferrochelatase. Regulation of HEM15 by light suggests a mechanism by which bwc1/bwc2 mutants are photosensitive and exhibit reduced virulence. We show that ferrochelatase is also light-regulated in a white collar-dependent fashion in N. crassa and the zygomycete Phycomyces blakesleeanus, indicating that ferrochelatase is an ancient target of photoregulation in the fungal kingdom

Tao3 mediates a phenotypic switch between amoeba-adapted and mammalian-adapted forms of Cryptococcus neoformans

Comparative Medicine - OneHealth and Comparative Medicine Poster SessionMany microbes are capable of changing phenotypes more frequently than due to basal mutation rates alone, and this ability is coupled to pathogenesis. The human pathogenic yeast Cryptococcus neoformans is found in the environment in soil, pigeon guano and tree species, locations in which the organism is exposed to microbial predators. Previous research showed that co-incubation of C. neoformans with amoeba causes a switch from a yeast to a pseudohyphal form, enabling fungal survival in amoeba yet conversely reducing virulence in mammalian models of cryptococcosis. We identify the basis for pseudohyphal development in phenotypic-switched and amoeba-derived strains, to show that genes encoding proteins of the RAM (Regulation of Ace2p activity and cellular Morphogenesis) pathway bear mutations. Reversion to wild type yeast morphology can occur through multiple different mechanisms to suggest that underlying rates of spontaneous mutation control this process and thereby influence the pathogenic potential of an organism

Transcriptomic responses of the basidiomycete yeast Sporobolomyces sp. to the mycotoxin patulin

Unprocessed Cuffdiff output of the RNAseq experiments performed for Sporobolomyces grown in the presence of 5 μg/ml of PAT. Where no Sporobolomyces gene models are indicated based on the previous JGI annotation (column C), it indicates a novel transcript identified following the transcriptomic analysis presented in this study. (XLSX 1622 kb

A glimpse into the basis of vision in the kingdom Mycota

Virtually all organisms exposed to light are capable of sensing this environmental signal. In recent years the photoreceptors that mediate the ability of fungi to " see" have been identified in diverse species, and increasingly characterized. The small sizes of fungal genomes and ease in genetic and molecular biology manipulations make this kingdom ideal amongst the eukaryotes for understanding photosensing. The most widespread and conserved photosensory protein in the fungi is White collar 1 (WC-1), a flavin-binding photoreceptor that functions with WC-2 as a transcription factor complex. Other photosensory proteins in fungi include opsins, phytochromes and cryptochromes whose roles in fungal photobiology are not fully resolved and their distribution in the fungi requires further taxon sampling. Additional unknown photoreceptors await discovery. This review discusses the effects of light on fungi and the evolutionary processes that may have shaped the ability of species to sense and respond to this signal.United States National Institutes of Health K22 AI073917National Science Foundation MCB-0920581Ministerio de Ciencia e Innovación BIO2009-12486Junta de Andalucía P06-CVI-01650, P09-CVI-502

Microarrays Reveal Early Transcriptional Events during the Termination of Larval Diapause in Natural Populations of the Mosquito, Wyeomyia smithii

overwinters in a larval diapause that is initiated, maintained and terminated by day length (photoperiod). We use a forward genetic approach to investigate transcriptional events involved in the termination of diapause following exposure to long-days. is up-regulated under long-day response conditions, is located under a QTL for critical photoperiod and is associated with critical photoperiod after 25 generations of recombination from a cross between extreme phenotypes. as a gene either involved in the photoperiodic switch mechanism or very tightly linked to a gene that is. We conclude that continued forward genetic approaches will be central to understanding not only the molecular basis of photoperiodism and diapause, but also the evolutionary potential of temperate and polar animal populations when confronted with rapid climate change

Antigen Diversity in the Parasitic Bacterium Anaplasma phagocytophilum Arises from Selectively-Represented, Spatially Clustered Functional Pseudogenes

Anaplasma phagocytophilum is a tick-transmitted bacterial pathogen of humans and other animals, and is an obligate intracellular parasite. Throughout the course of infection, hosts acquire temporary resistance to granulocytic anaplasmosis as they develop immunity specific for the major antigen, major surface protein 2 (Msp2). However, the bacterium then utilizes a novel recombination mechanism shuffling functional pseudogenes sequentially into an expression cassette with conserved 5′ and 3′ ends, bypassing host immunity. Approximately 100 pseudogenes are present in the only fully sequenced human-origin HZ genome, representing the possibility for almost unlimited antigenic diversity. In the present study, we identified a select group of 20% of the A. phagocytophilum HZ msp2 pseudogenes that have matched preferentially to human, canine, and equine expression cassettes. Pseudogenes cluster predominantly in one spatial run limited to a single genomic island in less than 50% of the genome but phylogenetically related pseudogenes are neither necessarily located in close proximity on the genome nor share similar percent identity with expression cassettes. Pseudogenes near the expression cassette (and the origin) are more likely to be expressed than those farther away. Taken together, these findings suggest that there may be natural selection pressure to retain pseudogenes in one cluster near the putative origin of replication, even though global recombination shuffles pseudogenes around the genome, separating pseudogenes that share genetic origins as well as those with similar identities

Congenic Strains for Genetic Analysis of Virulence Traits in Cryptococcus gattii

Cryptococcus gattii is responsible for a large outbreak of potentially fatal disease that started in the late 1990s on Vancouver Island, Canada. How this fungus and the outbreak isolates in particular cause disease in immunocompetent people is unknown, with differing hypotheses. To explore genetic contributions, a pair of congenic a and α mating type strains was generated by a series of 11 backcrosses to introgress the MAT locus from a nonoutbreak strain into the background of strain R265, isolated from a Vancouver Island patient. The congenic pair was used to investigate three traits: mitochondrial inheritance, the effect of the MAT alleles on virulence, and the impact of a predicted virulence factor on pathogenicity. The two congenic strains show the same virulence in different models of cryptococcosis and equivalent levels of competition in coinfection assays. These results rule out a role of the MAT locus and mitochondrial genotype as major virulence factors in the outbreak strains. Disruption of Bwc2, a light-dependent transcription factor, resulted in reduced virulence, consistent with a similar function in the related species Cryptococcus neoformans. The C. gattii congenic strains represent a new resource for exploring the evolution of virulence in the C. neoformans-C. gattii clade

The Tegument of the Human Parasitic Worm Schistosoma mansoni as an Excretory Organ: The Surface Aquaporin SmAQP Is a Lactate Transporter

Adult schistosomes are intravascular parasites that metabolize imported glucose largely via glycolysis. How the parasites get rid of the large amounts of lactic acid this generates is unknown at the molecular level. Here, we report that worms whose aquaporin gene (SmAQP) has been suppressed using RNAi fail to rapidly acidify their culture medium and excrete less lactate compared to controls. Functional expression of SmAQP in Xenopus oocytes demonstrates that this protein can transport lactate following Michaelis-Menten kinetics with low apparent affinity (Km = 41±5. 8 mM) and with a low energy of activation (Ea = 7.18±0.7 kcal/mol). Phloretin, a known inhibitor of lactate release from schistosomes, also inhibits lactate movement in SmAQP-expressing oocytes. In keeping with the substrate promiscuity of other aquaporins, SmAQP is shown here to be also capable of transporting water, mannitol, fructose and alanine but not glucose. Using immunofluorescent and immuno-EM, we confirm that SmAQP is localized in the tegument of adult worms. These findings extend the proposed functions of the schistosome tegument beyond its known capacity as an organ of nutrient uptake to include a role in metabolic waste excretion

Sexual reproduction is the null hypothesis for life cycles of rust fungi

Sexual reproduction, mutation, and reassortment of nuclei increase genotypic diversity in rust fungi. Sexual reproduction is inherent to rust fungi, coupled with their coevolved plant hosts in native pathosystems. Rust fungi are hypothesised to exchange nuclei by somatic hybridisation with an outcome of increased genotypic diversity, independent of sexual reproduction. We provide criteria to demonstrate whether somatic exchange has occurred, including knowledge of parental haplotypes and rejection of fertilisation in normal rust life cycles