Grass ( Fungus ( Virus ) Fungus ) Grass


in Science, The environment

Booth Street in snow

There is increasing scientific awareness of the intricate and essential ways in which different organisms depend on one another biochemeically. Termites could not eat wood without bacteria in their digestive tracts. Humans are likewise dependent upon the huge variety of microorganisms that comprise our microbiome.

Dichanthelium lanuginosum takes such intricacy a step further. It is a grass that lives in very hot soils – such as those in Yellowstone Park. ot only does it depend upon a fungus for its heat resistance, that fungus depends in turn upon a virus. Remove either the fungus or the virus and the grass can no longer live in its ordinary niche. Apparently, something similar has been observed in some tomato plants.

The example demonstrates just how shockingly complex the combination of biochemistry, ecology, and evolutionary biology really is.

Source: Márquez et al. “A Virus in a Fungus in a Plant: Three-Way Symbiosis Required for Thermal Tolerance.” Science 26 January 2007: Vol. 315. no. 5811, pp. 513 – 515.

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{ 7 comments… read them below or add one }

. December 20, 2007 at 2:23 pm
. December 20, 2007 at 2:31 pm

Unrelated but interesting:

How SUVs can save the climate
When is a Tundra is a better buy than a Prius?

You trade in your Civic, which averages about 32 miles per gallon, and buy a Prius, which gets a whopping 47 mpg. You’ve bumped up by 15 mpg — a big deal, right?

Sort of. Over the next 15,000 miles of driving, you’ll have reduced your fuel consumption by 150 gallons. That’s fine. But consider what happens when you upgrade your SUV. That’s where the real action is.

You swap out your Dodge Durango (16 mpg on average) for a Toyota Tacoma (23 mpg). It’s an upgrade of just 7 miles per gallon. It seems tiny. But consider that over the next 15,000 miles, you will have saved 285 gallons of fuel — nearly double what your fuel-sipping neighbor saved.

R.K. December 20, 2007 at 11:51 pm

Could this be used to make other plants more heat-tolerant?

. January 11, 2008 at 1:51 pm

Commensal (non-pathogenic) bacteria fill niches in our body and use resources that would otherwise be available to other pathogenic microorganisms. For instance, our skin and oral cavity are covered with bacteria, most of which will never harm us, as they live in a delicate balance with our immune system.

Peer reviewed science October 7, 2011 at 6:25 pm

Inside Job
Caroline Ash

Most plants only thrive in intimate associations with fungi—or arbuscular mycorrhizal (AM) fungi—and engage in mutualistic nutrient exchange with the plant. Some AM fungi have recently been discovered to have their own bacterial symbionts. Ghignone et al. have explored the genome of a newly discovered species of rod-shaped endobacterium that lives within vacuoles of the Gigaspora margarita AM fungus. The genome sequence of the endobacterium shows that it is unable to degrade starch or sugars, unlike the fungus, and indeed has a limited ability to import sugars from its host. What it can do, though, is obtain energy by breaking down amino acids extracted from fungal oligopeptides—and to alleviate this parasitism, the endobacterium has the capacity to synthesize vitamin B12 and thus potentially to donate this nutrient to its fungal host. This is not the symbiont’s only trick, because, like the pathogen Salmonella, the bacterium possesses the genes for the syringe-like type III secretion system, by which means it may inject various effectors across the vacuole wall. This genome offers another glimpse into the nested interdependencies we are beginning to expect to see when we observe microorganisms closely.

ISME J. 5, 10.1038/ismej.2011.110 (2011).

. July 17, 2012 at 12:17 pm

In all, the project showed that protein-coding DNA makes up less than
2 percent of our genome. At the same time, it showed that 8 percent of
our genome consists of old virus DNA that got inserted long ago and
never got cleaned out. (Some viruses, like HIV, have special enzymes
that insert viral DNA into human chromosomes; this insertion tricks
our cells into making viral proteins.) So by that measure at least,
we’re four times more virus than human

. April 23, 2013 at 11:00 pm

These viruses, admittedly, are acute. But she also has an example of a beneficial persistent virus. Her examination of a grass species growing in the hot and hostile environment of a geyser field in Yellowstone park showed that its heat tolerance was conferred by a virus that lives in a fungus which is, itself, symbiotic with the grass: no virus, no heat tolerance.

Dr Roossinck is now doing experiments in Costa Rica to look at virally induced heat tolerance in a range of plants and hopes to extend these in order to disentangle the advantages to their hosts of other sorts of persistent viruses. That would help to illuminate a view which is held by a rapidly increasing number of biologists, that many creatures (humans included) rely on symbiosis, rather than being self-sufficient. In the human case the symbionts are gut bacteria that help to process food, and also to regulate physiology.

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