Symbiosis: Enforced Surrender?

Symbiosis Enforced Surrender

Scientists from INRA and Lorraine University in France unraveled a key mechanism in the symbiosis between fungi and trees. During this mutually beneficial interaction, the fungus takes control of its host plant by injecting a small protein that neutralizes its immune defenses thereby allowing the fungus to colonize the plant. This finding is a major advance in our understanding of the evolution and functioning of symbiotic interactions between fungi and plants – relationships that play a significant role in supporting the health and sustainability of our natural ecosystems.

In the complex world of the rhizosphere – the soil surrounding plant roots – thousands of species of bacteria and fungi compete for resources released by plants. Some fungi, such as truffles and boletus, are able to live in symbiosis with plants through their roots, by-passing their competitors to obtain sugars directly from their host.  In return, symbiotic fungi allow plant roots to absorb mineral nutrients; this improves the plant’s health, vigor and productivity. Mycorrhizal fungi are one class of symbiotic fungi that make their way to plant roots where they negotiate for housing and all-you-can-eat sugar services. But how does this negotiation play out?  Is the host plant able to distinguish between beneficial and parasitic fungi? How does the fungus avoid the plant’s immune defenses during the interaction?

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Fungi Is Responsible For Majority Of Carbon Sequestration In Forests

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Northern boreal forests are easily recognized for their majestic trees and have been credited with helping to sequester much of the world’s carbon dioxide. It was originally thought that vegetative matter was what was sinking the greenhouse gas. Now, a diverse team of scientists from Sweden have discovered that these great, soaring plants are getting a lot of help from some humble decomposers living in the soil. Their findings, published in the journal Science, revealed that fungi were responsible for up to an incredible 70 percent of soil carbon in certain samples.

Researchers have long known that boreal forests were able to suck up a good deal of carbon, but were previously unclear as to where it went and how it was absorbed. They had thought that the carbon was carried to the tree’s needles and dropped to the forest floor where decomposition would leech it into the environment. If that were true, they would expect to find the newest carbon deposits close to the surface. However, after taking soil samples from over 30 islands and two small lakes in Sweden, they saw that the new deposits were more likely to be found farther down, pulled to the roots of the trees by fungus. The mycorrhizal fungus has evolved a special relationship with the trees where it colonizes in the roots and assists the tree. The fungus gets access to a more consistent stream of carbohydrates and other sugars, and the tree in return has access to more water and minerals.
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Plants Share Organic Nitrogen Which Aids Biodiversity

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Organic nitrogen gives new clue to biodiversity
Dated: 12 April 2006

Scientists have found that organic nitrogen is more important for plant growth than previously thought and could contribute to maintaining diversity in grasslands.

Until recently it was generally believed that the most important source of nitrogen for plants was inorganic nitrogen. However, researchers funded by the Biotechnology and Biological Sciences Research Council (BBSRC) from the University of Lancaster and the Institute of Grassland and Environmental Research (IGER) have found that not only can organic nitrogen be directly taken up by plants it is also used differently by different species, enabling nitrogen sharing and biodiversity.

By tagging organic nitrogen with stable isotopes researchers have challenged the long held idea that organic nitrogen has to be first converted into an inorganic form before the plants can use it. Their findings have significant implications in unfertilised, low-productivity grasslands where organic nitrogen often appears in greater concentrations than inorganic forms.

Professor Richard Bardgett, lead researcher at the University of Lancaster explained: “This research provides important new information about what happens to organic nitrogen in real ecosystems in real time. Tagging amino acids also revealed that different plant species prefer different sources of organic nitrogen. These preferences may be a way for plants and microbes to avoid competition with their neighbours for nitrogen when it is in very short supply, effectively enabling them to share nitrogen and maintain biodiversity.”

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Growing Asparagus In Meteorites To Prepare Us for Space Food

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For those of us without a green thumb, growing even the most hardy plants in perfect conditions can seem impossible. How about trying to grow plants on a meteorite? Well, at least one scientist is doing it, with moderate levels of success.

The thinking goes—if we’re going to have space colonies, we’re going to need some way to eat. Transporting all food from Earth isn’t realistic, and neither is bringing tons of bags of topsoil. Photos of asteroids, meteors, and other planets in our solar system look incredibly desolate, but, in fact, some of them contain many of the nutrients necessary to grow plants.

“People have been talking about terraforming, but what I’m trying to do is give some concrete evidence that it’s possible to do this, that it’s possible to grow in extraterrestrial materials,” Michael Mautner, a Virginia Commonwealth University researcher and one of the world’s only “astroecologists” told me. “What I’ve found is that a range of microorganisms—bacteria, fungi, and even asparagus and potato plants—can survive with the nutrients that are in extraterrestrial materials.”

Asteroids and meteorites often contain phosphate, nitrates, and even water that plants can feed on. Mautner thinks it’s not outside the realm of possibility to directly grow certain plants on other planets, in some sort of protected environment.

An asparagus seedling in meteorite soil. Image: Michael Mautner

He’s not simply tossing asparagus seeds onto a meteorite, however—he’s grinding up the rock into something more closely resembling soil. His plan is to eventually find several different plants and extraterrestrial soils that make the most sense to farm, and use his experiments to develop a “rating system” for which are likely to fare best—a kind of interplanetary farmer’s almanac, if you will.

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