Soybean: producing protein on a massive scale

US Department of Agriculture. Released into the public domain.

US Department of Agriculture. Released into the public domain.

This month’s organism is the soybean (Glyine max), a globally important crop plant that originates from Asia. The seeds (called soybeans) are rich in protein (40% of dry weight) and contain a good mix of essential amino acids needed by humans (1). Not surprisingly, this makes soybeans and their products popular with vegetarians and vegans as a source of non-animal protein. However, soybean-protein is also widely used as the main protein source for intensive farming of animals including chickens, cows and pigs.

Growing soybean a very efficient way to produce protein in terms of land-use. Soybeans produce twice as much protein per area of land than other vegetables or grain, and around 15 times more than land set aside for meat production (2).  The beans can be eaten whole after cooking (as in the Japanese dish edamame), but the majority of soybeans are processed to make a variety of soy-based food products, for example soya milk or tofu. Soy products are also added to many processed foods. Along with being rich in protein, soybeans are also rich in oil (20% of dry weight). The oil is extracted and used mainly for cooking with the remaining protein-rich pulp used as animal feed.

The Rhizobium species Bradyrhizobium japonicum lives in special plant organs called nodules on soybean roots. This is an electron microscopy image of individual rhizobium (stained dark) contained within plant cells in the nodule.

The Rhizobium species Bradyrhizobium japonicum lives in special plant organs called nodules on soybean roots. This is an electron microscopy image of individual rhizobium (stained dark) contained within a single plant cell in the nodule.

Soybean is a member of the legume family of plants. The seeds of other members of the legume family, including other beans, chickpeas and lentils, are also naturally protein-rich and widely cultivated. Legumes can afford to make their seeds more protein-rich than other plants can because they have a clever way for accessing nitrogen, an important plant nutrient required to make proteins. They can team up with soil bacteria called rhizobia to form a mutually beneficial relationship (symbiosis). In return for sugar and a place to live within the plant, the rhizobia convert nitrogen gas from the atmosphere into forms of nitrogen that the legumes can use. Relationships with rhizobia can give legumes a competative advantage over other plants, especially in low nutrient soils. Although rhizobia are naturally found in the soil, commercial strains of the Rhizobium species Bradyrhizobium japonicum are often applied to soybean fields to increase the number of symbioses established and maximise the nitrogen supply to the crop.

Cultivation of soybean began in China and Japan over 3000 years ago (3). During the 18th and 19th Centuries soybeans reached other regions including the Americas. In the USA it was mainly grown as a forage crop to feed livestock until the 1920s, when farmers were encouraged to grow it to increase the nutrient content of their soil (through release of excess nitrogen converted by the rhizobia). One of the soybean’s biggest supporters in the USA was Henry Ford, founder of the Ford Motor Company, who promoted the development of uses for soybean in food and industrial products (1). Today the largest growers of soybean are the USA, Argentina, China and India (1).

Like any other crop, cultivation of soybean is not without its challenges. Competition from weeds, damage by herbivores and diseases such as Soybean Mosaic Virus can all reduce soybean yields. One approach used in agriculture to better control weed populations is to grow genetically modified (GM) varieties of crop plants that are resistant to herbicides so that treatment with herbicide only kills the weeds, not the crop. The first GM herbicide-resistant soybeans were grown commercially in 1997. Since then, the use of GM soybean varieties has grown massively in many countries and by 2010, 93% of all soybeans grown commercially in the US were GM (1).

As a very land-efficient way of producing protein, it is likely that the demand for soybeans is going to continue to rise in the future. A challenge facing policy-makers is how to promote the production and consumption of soybeans without also promoting the destruction of some of the World’s most diverse natural environments, including the rainforests.

References:

1) Wikipedia: Soybean (Retrieved 04/09/2014)

2) National Soybean Research Laboratory Soy Benefits (Retrieved 04/09/2014)

3) Laws (2010) Fifty plants that changed the course of history. David and Charles.

Posted in Bacteria, Organism of the Month, Plants, Symbiosis | 3 Comments

Sugar helps plants to tell the time

The cacti in this sundial all have their own internal circadian clocks.

Clocks within a clock. The cacti in this sundial all have their own internal circadian clocks. Image by the author.

Plants can harness light energy to produce their own sugars from carbon dioxide and water in a process known as photosynthesis. Much of the sugar produced during the day is stored as starch to be used as an energy source overnight when photosynthesis is not possible. To enable the plant to maximise photosynthesis during the day and regulate the use of its starch energy stores at night, plants need to be able to “tell the time”. Plants have an internal “circadian” clock, which maintains 24-hour rhythms that modulate many plant processes, including photosynthesis.

At the core of the plant circadian clock are three proteins called CCA1, LHY and TOC1. These proteins (known as transcription factors) can regulate the production of other proteins. In the morning, the CCA1 and LHY proteins repress the production of TOC1 protein (see figure below). Over the course of the day, the levels of CCA1 and LHY proteins decline as their production is repressed by other transcription factors, including PRR7. With fewer CCA1 and LHY proteins to prevent its production, TOC1 levels rise at dusk and this further represses CCA1/LHY production. During the night TOC1 production falls and CCA1/LHY levels start to rise again. Continue reading

Posted in Cell Signalling, Plants | 2 Comments

Farewell lab bench, hello writing desk

IMG_3675Friday was my last day at the John Innes Centre. Although I’m happy to be moving on to new things, I’m going to miss the place and the wonderful people I’ve been working with over the last 5 years. In the past few weeks I have been preparing for my departure by wrapping up my experimental work, clearing out my lab bench, fridge and freezer drawers, and putting together a research paper to send to a journal.

Overall, I’m pretty pleased by what I’ve achieved research-wise over the last few years. I’ve tried lots of things, some of them worked, and I’ve got some interesting data that I’m still really excited about. I will definitely be keeping an eye on the field in future to see what happens next!
Continue reading

Posted in Life, Science Communication, the universe and everything else | 9 Comments

Sunflowers are turning heads

Sunflowers in Fargo, North Dakota, USA. Image released into the public domain by the United States Department of Agriculture.

Sunflowers in Fargo, North Dakota, USA. Image released into the public domain by the United States Department of Agriculture.

It is August and the sun is shining here in Norwich*, so what better plant to be the Organism of the Month than the sunflower?

Sunflowers are the subjects of some of Vincent Van Gogh’s most famous paintings, but they are cultivated for more than just their beauty. Sunflower oil, made from compressing sunflower seeds, is commonly used in cooking and to make biodiesel. It is the 4th most highly consumed oil in the World (behind palm, soybean and oil seed rape) (1). The seeds are also edible and are promoted as good sources of some vitamins, minerals and cholesterol-lowering compounds.

Sunflowers come from from the Americas and have been cultivated there for thousands of years (2). Native American tribes found a variety of uses for sunflowers. The seeds were ground up to make flour and the fleshy flower head used as a vegetable in cooking. Red, blue, purple and black pigments were extracted from the seeds to make dyes. The fibrous leaves and stems were used for the weaving of fabric and baskets. Sunflowers even had a role in worship of the Aztec’s Sun God. Although sunflowers first arrived in Spain in the early 16th century, it was Russia who first started producing sunflower oil commercially in the late 18th century (2). Russia remained the World’s largest producer of sunflower oil until the end of the 20th century, when it was overtaken by Argentina. Continue reading

Posted in Organism of the Month, Plants | Tagged , , | 10 Comments

My PhD in pictures

IMG_3736

Image by the author’s mother

Last Friday I donned a strange-looking outfit to graduate with my PhD. I had a lovely day with my family, and many of my friends who came back to Norwich to graduate. Despite having a certificate (and photographic evidence), it is still quite hard to believe that my PhD is now well and truly finished.

The last 5 years have been a mix of fun, exciting, busy, challenging and frustrating times. Overall, the good times more than outweigh the bad and I have learnt loads about science and myself along the way, so the experience was definitely worth the hard work.  To mark the occasion, I have put together some photos that represent my PhD journey. Continue reading

Posted in Life, the universe and everything else | 4 Comments

Leishmania parasites: neglected tropical killers

Later this year I will be visiting The Gambia in West Africa to work on a GirlGuiding community project. Before I go I will need to have some vaccinations to protect me from several of the diseases found there. Unsurprisingly, this has rekindled my interest in tropical diseases. This week, I have strayed from my usual subjects to write about the leishmaniases, a group of tropical diseases found across Africa, Asia and the Americas. Included in the World Health Organisation’s (WHO) list of Neglected Tropical Diseases, the leishmaniases are a big burden on public health services in many countries, and were responsible for an estimated 50,000 deaths worldwide in 2010 alone.

Leishmaniases are caused by parasitic single-celled organisms of the genus Leishmania. The parasites are carried between mammal hosts by several species of blood-sucking sandflies. The parasites live within the mouthparts of the sandflies and can be transmitted to mammals when the sandflies bite. The parasites exist in different forms in sandflies and mammalian hosts. In the sandfly, Leishmania cellsbecome promastigotes and move around the insect gut using string-like structures called flagella. Within a mammal host, the parasites “hide” within host immune cells (called macrophages) and lose their flagella to become amastigotes.

Leishmania parasite lifecycle requires sandfly and mammalian hosts. This image is a work of the Centers for Disease Control and Prevention (US Federal Government). The image is in the public domain (via Wikipedia).

The Leishmania parasite lifecycle requires both sandfly and mammalian hosts. This image is a work of the Centers for Disease Control and Prevention (US Federal Government). The image is in the public domain (via Wikimedia Commons).

Continue reading

Posted in Uncategorized | Tagged , | 1 Comment

Sabotage of plant cell communication by invading bacteria

Leaf speck on a tomato leaf caused by Pseudomonas syringae infection. Image by Alan Collmer via Wikimedia Commons (CC0).

Leaf speck on a tomato leaf caused by Pseudomonas syringae infection. Image by Alan Collmer via Wikimedia Commons (CC0).

To protect themselves from infection by disease-causing microbes, plants have systems that detect potentially harmful microbes and activate defence responses. Disease-causing microbes can overcome these defences by producing proteins called effectors that can enter host plant cells and disrupt them. Understanding what these effectors do in host plants could be useful for the development of more disease-resistant crop plants. Unfortunately, the roles of many effector proteins are not yet understood.

One of the ways effector proteins can interfere with plant defence responses is to prevent the relay of danger messages from the site of microbe detection at the plasma membrane to other locations in the cell. For the signal relays to function, the various protein components need to be located in the right places in the cell (plasma membrane, cytoplasm, nucleus, vacuole etc.). The cytoskeleton, consisting of filaments of the protein actin, is required for this organisation and moves proteins contained within (or on) small membrane-bound structures called vesicles. Continue reading

Posted in Bacteria, Cell Signalling, Plants | 3 Comments