The Little Fungus that Could

By Nathan Smith

Deep in the dark depths of fungal taxonomy there lies a phyla known as the Glomeromycota. Members of this phyla are all obligate symbiotes, unable to support themselves independently and requiring a photosynthetic partner to provide organic carbon to them in return for gifts of phosphorous and nitrogen. For all bar one, this photosynthetic partner is a terrestrial plant; the symbiosis being better known as Arbuscular Mycorrhization and which upwards of 80% of angiosperms (flowering plants) are capable of engaging in.

The exception to this Golden Rule of the Phyla? A species known as Geosiphon pyriformis which instead forms a relationship with the cyanobacteria, specifically the species Nostoc punctiforme.

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Geosiphon:Nostoc symbiosis; Geosiphon spores inset
(credit Schuessler Lab)

The Geosiphon:Nostoc symbiosis appears to be unique in nature as the only example of an endosymbiosis between a fungus and a bacteria.  Adding to its mystery, it has so far been reported to have been found only 6 times in the wild in a small region of eastern Germany and Austria.

In contrast to Arbuscular Mycorrhization, where the fungal partner invades the cells of the plant to create an exchange interface, the cyanobacteria are taken in by the fungi, surrounding them with a unicellular structure known as a ‘bladder’ that can grow up to 2mm in length.

The exchange of nutrients is also different than in Arbuscular Mycorrhization. With the exception of nitrogen and carbon, all of the cyanobacteria’s nutritional needs must be met by the fungus. In return, the fungus receives organic carbon and nitrogen.

It is possible that Geosiphon:Nostoc symbiosis represents an important step in fungi being able to form symbiotic relationships with plants; it’s also possible that the Geosiphon:Nostoc developed out of the wider spread Arbuscular Mycorrhiza symbioses.

Either way it’s an interesting story of one fungus breaking the mould.

Plants in science fiction and fantasy

By Lilian Halstead

When it comes to plants in real life, many people seem to think that because they don’t move, they can’t be very interesting. This is hardly the case in science fiction, where plants (and plant-animal hybrids) are much more active, dangerous things. If you think of plants in science fiction the thing you are mostly likely to come up with first would be the triffids, which first appear in The Day of the Triffids. These intelligent flowering plants originally kept for their oil escape and take over, killing with a venomous sting and wondering around on three stumpy legs. Another well known dangerous plant is Audrey II from the Little Shop of Horrors, which although it remains rooted in place manages to persuade Seymour to bring it the flesh it needs to grow.

These man eaters are by no means the first though— there is a long history of claims of trees that eat people during the exploration of Africa by the Europeans, although they tended to be depicted as masses of tentacle vines which would lash out and grab the unwary, much like the bloodoak and tarryvine in the Edge Chronicles. Some aspects of their design are echoed in the more benign whomping willow in Harry Potter, which is more grumpy than hungry. Many of the plants in the Harry Potter books are drawn from folklore: the devil’s snare was a bloodsucking vine believed to grow in central America, while the mandrake is a real plant which has fleshy roots that was said to scream to kill those who uprooted it.

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Some Arthurian legends say Merlin was turned into an Oak tree by Niviane
(Credit Rob Young)

Another common theme is for plants to resemble people. In Invasion of the Body Snatchers people are gradually replaced by replicas grown in pods. But others are more friendly, one of the main characters in Farscape is a humanoid plant, although it’s not possible to tell from looking at her. Ents are more typically what you’d expect from plant people, and the Cactacae in the world of Bas-Lag are also more plantlike, having wooden bones and being covered in spines. In mythology there were the dryads, tree spirits in humanoid form, although in myths people also had a habit of turning into trees. In some versions of the Arthurian legends Merlin suffers this fate, doomed to live as an oak by the actions of Niviane.

As well as plant people, plant-animal hybrids tend to spring up all over the place. The Sarlacc from Star Wars is one of these, some expanded universe depictions describe it as having roots as well as tentacles and teeth. The best hybrid though has to be the vegetable lamb of Tartary, which is exactly what it sounds like—a plant shaped like a sheep attached to the ground by an umbilical cord-like stalk.

Despite all these plant monsters and hybrids, the most common use of plants is as a MacGuffin: they are variously able to cure diseases, kill the invincible monsters, lift curses and even, in some folk tales, open locked doors. So while animals may get most of the glory in most of science fiction and fantasy, there is also no shortage of plants.

Invisible forests; and how marine dwelling microorganisms really rule the waves!

By Charlie Whittaker

For sure, the abundance of terrestrial plants we share our planet with are weird and wonderful in equal measure, but why should they get all the glory when there’s an equally as important component to the biomass on Earth? I’m of course talking about the much maligned, often overlooked, and most definitely misunderstood microscopic creatures that inhabit the murky depths of our oceans!

The marine environment is by far the planet’s largest habitat. Covering over 70% of the land area, it contains a huge diversity of organisms, co-existing in a harmonious, yet fragile, balance. Underpinning all the life that the oceans sustain are photosynthetic organisms. Tiny, often microscopic and unicellular, these organisms are responsible for roughly half of all the primary productivity of the planet. Their ability to capture sunlight and use it to synthesise new organic compounds provides the energy for the diversity of marine life found in the ocean. They are, for want of a better analogy, the oceans’ invisible forest.

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These primary producers are exceptionally diverse, ranging from tiny photosynthetic bacteria that hitch a ride on the tiny particulate matter found in seawater, to the phytoplankton. These represent a hugely diverse group of unicellular organisms. Contained within this group are the diatoms, which enclose their cell in a glass box made out of silica, as well as the dinoflagellates, that tend to employ semi-opaque plates of cellulose to separate themselves from the external environment. And then who could forget the coccolithophores? Unicellular like their other phytoplankton counterparts, these microorganisms cover themselves with ornamented plates called coccoliths made out of calcium carbonate.

So why does any of this matter?

80 million tonnes of marine seafood are caught globally each year. Seafood forms a common constituent of diets worldwide and provides more than 1.5 billion people with at least 15% of their protein requirements. The entirety of this marine life, whether directly (animals that feed on the producers themselves) or indirectly (in the case of organisms several trophic levels above the primary producers), relies upon the productivity and photosynthesis these organisms are carrying out.

They also represent an important carbon sink. The ocean plays a huge role in mopping up and buffering CO2 released into the atmosphere: and a significant proportion of the ability to do this stems from the simply huge amount of photosynthetically capable biomass present.

Okay, that’s fine and dandy then?

Not quite. Unfortunately things are getting progressively less peachy. Climate change poses a serious issue to the future productivity of the oceans and marine life. Changes to the oceanic average temperature has implications ranging from alterations to the vertical stratification of the water column (important in mixing, thereby ensuring all the phytoplankton receive all the nutrients they need) to impacting the chemical reactions responsible for the productivity of the primary producers. Whilst of course, the response to rising sea temperatures will not be the same globally (a paper recently published in nature showed that “Some phytoplankton like it hot” and that warming oceans may increase productivity in some areas) there are important marine areas of human concern that are set to suffer substantially: the Atlantic Cod population has plummeted in number in recent years. Partly this has been driven by overfishing, but it was also shown this was due to rising temperatures. The alteration modified and impacted the plankton ecosystem in such a way that it reduced the survival rates of young cod, and thereby facilitated the population’s rapid decline.

They may be invisible, but the effects of these tiny photosynthetic powerhouses are quite the opposite. And unless something is done soon, they may be at the forefront of drastic alterations to our current marine system.

Further reading:

On the effect of increased temperatures on cod and phytoplankton populations.

On the propensity some phytoplankton show for warmer temperatures.

Marine Biology: A Very Short Introduction.

You’ve got the wrong (fun)guy!

by Nathan Smith

If you were presented with a plant and a fungus and asked to pick the parasite, chances are you’d pick the fungus. Whilst this is often the case, there are significant and widespread cases of the relationship being the other way around. Enter Orchids.

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Common Spotted Orchid

Orchids are family of plants distinct in physical appearance and are renowned for their sweet scent and aesthetic beauty, despite the fact they more closely related to rice than they are to roses. Their seeds contain rather small reserves of nutrients and they are unable to photosynthesise immediately after germination, instead going through an achlorophyllic stage; in fact some orchids are not capable of photosynthesis during their lifespan. Usually small reserves and an initial inability to photosynthesise would be considered a bad strategy for a plant, but Orchids are still thriving and there is a good reason why.

Throughout their non-photosynthesising stage, and indeed throughout their entire existence, they are the dominant partners in what can best be described as an uneven symbiotic relationship with a fungal partner.  In fact, a fungal partner is required by the orchid for them to germinate ‘in the wild’. Orchids can be germinated in sterile conditions; however this requires exposure to the ‘fungal sugar’ trehalose.  So what is the trade between the orchid and the fungus?  The fungus supplies the plant with organic carbon, a source of nitrogen, phosphorous, and other minerals and nutrients, and in return, gets… well, not much really. This uneven relationship continues once the plant gains the ability to photosynthesise and there is little evidence that the fungus gains a significant amount of reduced carbon from its photosynthetic symbiont. The fact that the fungus enters into a symbiosis with the plant in the first place, and continues this relationship throughout the plant’s life, suggests the fungus gains something from the relationship or that the plant emits a strong attractant, however there is little to no evidence for this and so these hypothesises remain little more than speculation.

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Tway-blade Orchid

What about the orchids that never photosynthesise? These plants, for instance the Bird’s-nest Orchid, have a habit of forming symbioses with fungi that also associate with tree roots. This allows them to use the fungus like a straw and indirectly parasitise what they need from the unsuspecting trees. Clever stuff.

Orchids are beautiful and interesting plants and deserve to be admired, but it doesn’t mean it’s the good guy. Next time spare a thought for the poor little fungus.

Photography by Leanne Massie

Trees: Carbon Sinks or Sources?

by Joanna Wolstenholme

With a warming planet, you wouldn’t be laughed at for thinking that trees may come to our rescue: we release more CO2, the greenhouse effect leads to global warming, and this increase in temperature leads to plants being able to photosynthesise faster. Indeed, future climate warming is expected by many experts to increase plant growth in temperate ecosystems, and increase carbon sequestration. So is our planet coming to the rescue, is Gaia saving us from certain doom? Well, unfortunately, no. Heatwaves lead to droughts, and droughts put plants, trees in particular, under a lot of stress. Without sufficient water, plants struggle to transpire, and so are unable to take up enough nutrients and water for growth.

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Ciais et al (2005) found that during the heatwave and drought of 2003, plants in Europe managed to undo four years of their own carbon sequestration, by reverting to sources rather than sinks of carbon. Growth primary production was severely reduced, and respiration in plants and soil microbes fell dramatically. They suggested that increased extremes of temperature, as have been predicted if we fail to reign-in climate change, may counteract the effects of the mean warming and lengthened growing season.

This work was put into stark contrast by the 2005 and 2010 droughts in the Amazon. Usually, the Amazon acts as a vast carbon sink, absorbing 25% of atmospheric carbon, making it an important buffer against climate change. However, increased occurrence of droughts could lead to it becoming a net carbon source – a catastrophic positive feedback system which would cause a vast acceleration of climate change. The 2005 drought led to the release of approximately 1.6 billion tonnes of carbon to the atmosphere, and as much as 2.2 billion tonnes of carbon could have been released from the Amazon during 2010. That is about one-quarter of global emissions from fossil fuel use. The Amazon is such a vast forest (25 times the area of the UK, to put it into perspective) that even low level drought damage can have a large overall effect, and this is likely to be impounded in the coming years by more frequent drought stresses, even at a low level.

400px-DroughtNonetheless, fear not – a report published last year by University of Exeter and Colorado State University cast a more positive slant on the situation. They believed that previous models had failed to take into account the amount of water that the forest itself is able to recycle during droughts. As moisture cycling is normally a source of a third of the water rainforest plants use, it has the potential to act as a buffer during times of drought. However, moisture cycling is severely impacted in disturbed forest, so in order for the Amazon to still withstand periods of drought, forest conservation measures must be strongly enforced.

Lets hope the academics from Exeter and Colorado are right, and that the Brazilian government are able to protect their amazing forest. In the mean time, do your own little bit – plant a tree!

For more information, see: 

Ciais et al, 2005. ‘Europe-wide reduction in primary productivity caused by the heat and drought in 2003’. Nature 437 doi:10.1038/nature03972

Super-domestication: making plants work for us

by Leanne Massie

Super-domestication is a relatively new term to describe plants that we have modified to extremes to fit our own needs. For example, crops that have huge yields with minimal negative effects on the environment could be called super-domesticates.

These crops are still works in progress though; the most notable super-domesticate-to-be is “C4 rice”. Rice is naturally a C3 plant, which means it uses a less efficient method to capture carbon from the atmosphere. Some plants that are adapted to hot, dry conditions have evolved a different carbon capture mechanism called C4 photosynthesis, which allows them to take up more carbon dioxide and lose less water in the process, a sort of supercharged version of photosynthesis. If C4 photosynthesis could be introduced into rice the benefits are staggeringly huge. Yields would be increased while at the same time water use would go down. In a world where water shortages are starting to affect everyone and where rice already provides more than one fifth of the total calories consumed worldwide, a C4 variety of rice would go a long way to ending world hunger.

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Credit: Dalgial

This isn’t an easy process though; introducing C4 into a C3 plant is like trying to compare pricing at a supermarket, extremely difficult!. It can be done but takes huge amounts of effort and determination.  But fortunately, C4 photosynthesis has evolved more than 50 times in nature so with the right tools it is very feasible. The C4 Rice Consortium, a foundation that has more than 600 scientists worldwide, has been working on introducing C4 photosynthesis into rice since 2008 and the researchers have collectively published over 400 papers relating to C4 rice since. The scientists are well on their way to making rice into a super-domesticate.

However, this is only rice. Wheat, corn, potatoes, tomatoes, and peas are just some of the other crops that are also being studied to make them work harder for us. Imagine the possibilities that super-domestication could bring if all our crops were supercharged to their full potential.

For more information, see:

C4 Rice Project. http://c4rice.irri.org

D.A. Vaughan, E. Balazs, J. S. Heslop-Harrison (2007) From Crop Domestication to Super-domestication. Annals of Botany 100: 893-901

Controversial anti-GMO study retracted

By Sophie Harrington

In November 2012, researchers from France shocked the world when they published a highly controversial paper claiming that there was a link between genetically modified foods and the incidence of cancer. The work by Dr Gilles-Eric Séralini and his team from the University of Caen, France showed that feeding rats Roundup-resistant maize was leading to the growth of tumours in lab rats. However, after a year of heated debate and outcry in the scientific community following the publication of the study, on 20 November the paper was retracted by Food and Chemical Toxicology, the journal which had originally published it.

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A blow for anti-GMO activists?

Shortly after its publication, concerns were raised over the quality of the data used in the paper, outlined in various letters to the editor of the journal. These included the small sample size of each test group, inconsistent interpretation of results, and apparently contradictory results that were not addressed by the authors.

Additionally, the strain of rats Dr Séralini chose to use is known to have a higher incidence of cancer, particularly in old age. The study considered the development of cancer over two years in rats, which is near the end of the rats’ natural lifespan. It has been suggested that the high incidence of cancer the study reported was due to the strain’s propensity to develop cancer late in life, rather than due to their exposure to GMOs.

The decision to retract the paper is controversial in itself. Questions have been raised regarding the decision to retract a paper without evidence of fraud or misrepresentation of data. It appears that the decision to retract was taken with the view that the paper should never have been published in the first place. In a letter announcing the proposed retraction, William J. Hayes, the editor-in-chief of Food and Chemical Toxicology, stated that the results are inconclusive, and consequently “do not reach the threshold for publication.”

Unsurprisingly, Dr Séralini has condemned the decision to retract. Since its publication, the paper had been cited 28 times, and Dr. Séralini has been called to testify before the French National Assembly on the paper. Critics of the decision have called out the ostensible conflict of interest seen in the recent appointment of an ex-Monsanto employee to the post of associate editor at Food and Chemical Toxicology; Monsanto is currently the world-leader for the production of GMO foods, and it also produced the GM strain of maize used in the study.

The retraction of this paper has been seen by many as a victory for many in the scientific community who support the safety of GMOs. It remains to be seen, however, whether backlash by those concerned with the reasoning behind the retraction will increase the controversy over genetically modified organisms.

For more information, see Retraction Watch’s coverage of the event: http://retractionwatch.com/2013/11/28/controversial-seralini-gmo-rats-paper-to-be-retracted/

Details of the retraction letter and further discussion of the paper can be found here: http://www.sciencedirect.com/science/article/pii/S0278691512005637

Maize 1507: The crop of European fear and indecision

By Nick Dinan

Most of us know that maize is one of the four staple crops for human nutrition, rice, wheat and potatoes being the others. Considering global food insecurity, in what ways could we make this crop better? Perhaps the more urgent question is how have betterments to the crop been restricted, particularly within the ever-skeptical European Union.

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Credit: Australian Aid

1507 maize is a genetically modified version of maize produced by Pioneer DuPont with the aim of being cultivated within the EU. This variety of transgenic maize has the ability to produce an insecticide (Bt-toxin), derived from genes of the bacterium Bacillus thuringiensis. 1507 maize is protected from pests such as the European corn borer – caterpillars of this species chew tunnels that compromise the structural integrity of Maize, destroying it in the process.

The crop was first presented in Spain in 2001. However, a chain of bureaucratic constraints, with repeated drafts of proposals for the crop being delayed due to the indecision of the European Commission, has delayed 1507 maize’s entry into the European market for 12 years. Ever most concerning is that 1507 maize meets all of the European Union’s regulatory requirements for genetically modified crops, such as safety compared to the original crop.

Reservations about 1507 maize are clear – can we ingest a toxin that has the capacity to kill insects? Maize is one of our staple crops; won’t the over-consumption of such a toxin have long-term adverse effects on our health? Who would want to feed their child toxic corn? Copious amounts of research refute these reservations.

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Credit: Les Haines

The proteins expressed in 1507 maize (Cry1F & Pat) that produce the Bt toxin are not toxic or allergenic to humans and animals. You might say we’re unsure of the long-term effects of the Bt toxin – how do we not know that there isn’t a network of dangerous pathways the toxin may ignite? Quite simply, there isn’t – creation of 1507 maize is not intertwined with the application of the Bt toxin. In fact, Bt sprays have had a history of controlling insect pests by spraying since the 1920s, where it is universally understood to be safe due to the specificity of the chemical for pests. Furthermore, 1507 maize and maize have nutritional equivalency, as well as identical risks of hybridization with wild populations (very low) and levels of environmental impact. It did not take 12 years to discover these facts; in 2005 the GMO Scientific Panel of the European Food Safety Authority (EFSA) concluded 1507 Maize to be just as safe as ordinary maize.

Only on the 6th of November did the European Commission approve cultivation of the crop. The concerns of a GM-conservative government and populace was embodied in protests from environmental groups about safety, despite frustratingly manifest evidence that should have silenced their qualms.

This is the third GM crop to be approved for cultivation in the European Union. We could perceive this as a victory, but ultimately this huge delay represents the unwarranted skepticism of the developed world towards GM crops. Perhaps we don’t have the same degree of urgency, eradicated by the luxury of huge choice in what we eat. The organic, “gene-less” tide may be okay for now, but we’re at the risk of creating a culture not based on efficient cultivation that will be required in the future.

Blurred Lines: Tomatoes, Tobacco and Potatoes

By Nathan Smith

Tomatoes, Tobacco, and Potatoes all seem rather different produce and, as far as man is concerned, all have different uses tomatoes for food, tobacco for smoking, and potatoes for toddlers’ first ventures into the world of art but they are in fact all members of the same plant family, the Solanaceae, and as such have a rather similar genetic framework.

Indeed this genetic similarity allows for some rather groovy biology. Recall if you will the cultural event that was The Simpsons, specifically the episode “E-I-E-I-(Annoyed Grunt)”. If the name sounds unfamiliar, this was the episode where Homer flees from a duel and decides to become a farmer. Using plutonium as a fertiliser, he inadvertently creates Tomacco, a hybrid between a Tomato and Tobacco plant. It sounds silly, even cartoonish, but could it actually happen?

Credit: Alan Levine

Credit: Alan Levine

Well…kind of. Tomato plants grafted to tobacco roots resulted in exceedingly high levels of nicotine in tomato leaves and up to a 100x increase in the nicotine amount of the fruit itself. Though, alas, the nicotine content of the fruit was negligible when compared to that of tobacco leaves.

Tomatoes have also been grafted with potato roots, resulting in a plant that produces cherry tomatoes above soil and potatoes below soil. Glorious.  And the best bit? After research exceeding 15 years, the plants are now commercially available. They are sold by the Ipswich-based company Thompson and Morgan under the trade name TomTato for the slightly dear price of £14.99.

Another member of the same family is Deadly Nightshade, but please don’t try to graft this to another species. I prefer my chips when they’re not trying to kill me.

Defusing the Biosphere: Plants, Explosives and Contaminated Battlefields

by Charlie Whittaker

Toxins and pollutants that are the by-products of industrial processes are one of the most serious environmental issues of the 21st century. They render land uninhabitable, pollute both water supplies and the atmosphere, and can cause a variety of costly and debilitating illnesses along with it. Removing these pollutants, from wherever it may be they accumulate, is usually a very costly and time intensive affair. Most processes rely on physical destruction of the matter they have contaminated. However, a great deal of work is going in to providing other avenues of opportunity for decontamination. One of these is phytoremediation.

Phytoremediation involves using plants to solve these very problems. In doing so, decontamination can be achieved without any need to excavate and transport contaminated material: the entire process of detoxification can be done on site, preventing irreversible destruction of the environment that can occur with other methods as well as reducing cost.

Phytoremediation is not a new idea, and many plants have already been utilised to remove toxic contaminants from the soil. Alpine pennygrass has been in use for a long time due to its ability to hyperaccumulate the poisonous metal cadmium. However, a new direction in the field is to utilise metabolic pathways found in other organisms, and then genetically engineer them into plants, with the potential to vastly increase the types of toxins plants can deal with.

RDX

RDX is a nitroamine based explosive widely used in both military and industrial application and which is far more powerful than TNT. First used during World War II, RDX is still used in the bulk of explosives employed today. Extensive military activity involving RDX over long periods of time has resulted in widespread and severe contamination of the soil with the material. This contamination affects both the land used during the military exercises, but also more concerningly, the groundwater contained beneath it. RDX is toxic; thus, this represents a substantial safety issue.

Natural degradation rates of RDX in the environment are low, and the strategies currently employed (such as incineration and composting of the soil) are incredibly expensive. However, nature has one trick up its sleeve. A number of different bacterial species were found that possessed metabolic pathways resilient enough to process and decontaminate the RDX molecules, rendering them harmless and providing the bacteria with a source of energy.

Credit: Alberto Salguero Quiles

Taking advantage of this, one group of scientists engineered the protein, called XplA/B, responsible for RDX degradation in bacteria, into the plant Arabidopsis thaliana. The plants were transformed, and demonstrated an incredible ability to grow in soils so concentrated in RDX to have killed plants not possessing the protein. The plants were able to take up these toxic explosives, and store them safely.

Ongoing work is looking at introducing these modified plants into decommissioned military operation sites. At the moment the concentrations of RDX in the soil are so high as to have killed off most if not all of the native species present there, as well as rendering the land uninhabitable. The hope is that, through the use of these plants, effective phytoremediation can occur, and the explosives can be removed from the soil.

This article originally appeared in Varsity