Tag Archive: plant pathology


It is a lovely spring day and I am absorbing some sunlight, hanging out in the tail end of the Carrboro Really Free Market while I type up my notes on the Duke Mycology Symposium. [CLICK HERE FOR DAYS ONE AND TWO]

There were a couple of posters which really caught my eye. One thing that I think is very interesting about fungi is their symbiotic relationships with plants. So I was excited when I saw two posters, both put together by Ryoko Oono and colleauges: “Populations structure in Lophodermium spp., a common fungal endophyte of loblolly pine” and “Effcts of foliar fungal endophyte diversity on plant protection against pathogens”. The first presents some preliminary information about the distribution of Lophodermium amongst pine trees in North Carolina. They found that there are three distinct subgroups of the of the fungus, despite not being geographically isolated. This suggests that there is limited gene flow between the subgroups. The second poster discusses the ecological role of fungal symbiotes: both single and multiple fungal colonizations can increase pathogen resistance, and since individual fungi types antagonize specific pathogens, you might expect a diverse group of colonizers to repel the most pathogens. However, there may also be a sort of tragedy of the commons effect, in which the individual members of diverse group of symbiotes have no particular dedication to protecting the host plant. Clarifying these issues will require more research, and the poster outlines a plan for further study.

The biochemistry of metals was a recurring theme in this symposium. We’ve already looked at iron, nickel, and cobalt; so let’s wrap up our tour of the transition metals with “Copper homeostasis as a virulence factor in systemic infection by the human fungal pathogen Cryptococcus neoformans,” by Chen Ding and colleauges at Duke. They describe the susceptibility of Cryptococcus to copper toxicity in the host, and the role of a class of biomolecules called metallothionens in protecting Cryptococcus from the metal. Interestingly, they also present data showing that copper levels are elevated in the serum of Cryptococcus patients – evidence, perhaps, for the immune system incorporating copper into its chemical weaponry! This would be the exact opposite reaction that it has when it comes to iron, which it withholds in an attempt to starve pathogens of nutrients (Nesse and Williams 1994; p. 29-30)

Yeast colony macrostructure - photo from the Magwene Lab - click to visit them

Finally, there was “Genetics, genomics, and variation in yeast colony morphology”, presented by Josh Granek and colleagues at Duke. They studied the yeast saccharomyces cerevisiae under a variety of different growing conditions. They found that, under conditions of abundant nitrogen but scarce fermentable carbon, the yeast colonies developed complex, organized structures large enough to see with the naked eye. This sort of emergent behavior is very interesting; it shows the bottom-up organization of biology by which relatively simple units can have complex system-level behavior … and understanding how cells communicate and cooperate in a colony can provide insights to the transition from unicellularity to multicelluarity.

That’s all there is to say about the symposium. One thing that I have been thinking about is the involvement of mycology communities in doing environmental monitoring. Simple citizen science monitoring programs already exist for animals and plants (Cohn 2008). Why not monitor the third domain of eukaryotes? Mycological enthusiasts already have local clubs, and the data gathered could provide insights into fungal biogreography and ecological change.

Further Reading
Cohn, J. (2008). Citizen Science: Can Volunteers Do Real Research? BioScience, 58 (3) DOI: 10.1641/B580303

Randolph Nesse, & George Williams (1994). Why We Get Sick: The New Science of Darwinian Medicine. Vintage Books: New York

I’m going to take a break from our regularly scheduled debunking of John Everett’s Senate testimony, to pose a question for creationists and cDesign Proponentsists: Why do people catch swine flu but not tobacco mosaic virus?

I’m not asking why people get sick. I’m not interested in a rehashing of the tired old arguments about the coexistence of god and human suffering. I want an explanation of the fact that, despite the myriad pathogens which infect other branches of the tree of life, it’s only pathogens from other animals (usually other vertebrates) which make humans sick. Poxes, tuberculosis, and anthrax infect cattle. HIV is a mutant variant of Simian Immunodeficiency Virus, which infects other primates. Why don’t we fall ill from Partitivirus, pathogen of fungi? Or T4 phage, parasite of bacteria?

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