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Issue One 2014 - Issue #20

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Wheat seedlings sprout ideas on future food supply protection

Story by Mandy Thoo

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edward linacre

In a quest to produce better quality wheat to feed the world, a team of researchers has turned its attention to the workings of a particular antibacterial protein. They found that the protein is aggressive towards a wide range of bacteria and fungi, but leaves mammalian cells unharmed. The implication of this for antibiotics, health, food and the wheat industry is vast, and it all stems from a few genes in the small and humble wheat seed.

This finding is a collaborative effort of plant molecular biologists and microbiologists. Published in the scientific journal PLOS ONE, the study was carried out by Swinburne’s Professor Mrinal Bhave, Professor Enzo Palombo and Rebecca Alfred, together with Dr Joe Panozzo, a senior research scientist at the Victorian Department of Environment and Primary Industries.

Understanding a food staple

Professor Bhave, whose research interests include how genes control grain quality, says that wheat is the staple food of 35 per cent of the world’s population and the third largest cereal crop after maize and rice.

“There are two types of wheat – the ‘natural’, soft, wheat and the hard type,” she says. Soft wheat is mainly used for soft baked goods, such as cookies and cakes, whereas hard wheat is used to make pasta and breads.

Alfred, whose doctoral research was sponsored by the project, explains that the harder the grain, the higher its price: “This is due to the higher protein content in hard grains, which produces flour of better quality.”

Due to the high commercial value of hard grains, scientists have focused their research on two genes that determine grain hardness – puroindoline a and puroindoline b (Pina and Pinb). The presence of both genes in the wheat seed results in soft wheat, whereas any mutation that leads to the loss of either Pina or Pinb gives it the hard texture.

Natural protection

And as researchers strive to identify existing and new mutations to produce more – and better – hard wheat, the Swinburne team went after another function of these genes – their ability to protect wheat seedlings from bacteria and fungi.

These peptides – short chains of protein-building blocks which stem from Pina and Pinb – are known for their antimicrobial properties and are implanted in various crops. However, how these peptides defend wheat seedlings from diseases remained a mystery, says Professor Bhave.

“But it’s crucial to know how the peptides work, especially if we plan to use them in agricultural or medical applications,” adds Alfred.

So Alfred, with the guidance of the supervisory team, designed artificial peptides that mimic the ones found in grains. They then tested these peptides against various bacteria, fungi and mammalian cells.

The researchers found that the peptides’ mode of attack is aggressive and broad: the peptides not only disrupt the membrane – the protective layer of cells made of lipid – but they travel further into the cell and stop the replication of DNA which is what all organisms do to survive. By destroying the main machinery that all cells have in common, Alfred explains that these peptides can work against many types of bacteria and fungi.

“But we found that more importantly, they do not attack mammalian cells,” says Professor Palombo. “This is because bacteria and fungi membranes are positively or negatively charged, which attracts the peptides to bind to them. The membranes of mammalian cells, on the other hand, are neutral, so the peptides don’t have an ‘affinity’ for them, leaving them alone.

“This means they’re selective, which is great for antimicrobial drugs – we want them to target the harmful cells while leaving our own unharmed.”

Reduced contamination

Professor Bhave adds that the peptides can be used in any area that aims to reduce microbial contamination, such as food safety, hygiene and surface decontamination.

“These peptides can also tolerate high heat, so they can also be used in food applications, including putting them into milk or orange juice,” says Alfred. “They can survive and still protect any drinks that have been sterilised with ultra-high temperature.”

The team is currently modifying these peptides and testing them against more bacteria and fungi. “Now that we know how they work, we can develop peptides to target a particular bacterium. We can also modify them to make them more effective,” says Professor Palombo.

Dr Joe Panozzo says the team’s work has provided the Australian wheat industry an edge in the highly competitive market. “We need to develop wheat of better and better quality in order to compete, and this includes hard wheat resistant to plant diseases.

“So the more we understand the role of the puroindoline genes at a molecular and genetics level, the more room we have to improve wheat quality. We are now carrying out more research based on this information to produce new wheat varieties with an enhanced quality.”

Dr Panozzo says that the scholarship provided by the project is a good opportunity for research students – such as Rebecca Alfred – to experience a non-academic research environment, such as a plant breeding centre. “It exposes the students to new perspectives, where they find out how their research work may be transferred to its related industry.”

Rebecca Alfred has now obtained her PhD based on her research on grains.

National wheat production 2011–2012
29,515,000 tonnes of Australian wheat produced (the highest yield since 1861).
Source: Wheat Exports Australia Annual Report 2012–13

National wheat exports 2011-2012
23,000,000 tonnes of Australian wheat (compared to 20.4 million tonnes exported the previous year).
$6.38 billion contributed to Australian export revenue annually by wheat production.

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