Giving rice new weapons to fight rice blast disease

Understanding how a fungal pathogen interacts with rice cells could help us engineer new defences 

Rice is one of the world’s most important agricultural crops, with 741.5 million tonnes produced in 2014. A large proportion of the global population relies on rice as a staple food, particularly in Asia and Africa. However, harvests are threatened by rice blast disease, caused by the fungus Magnaporthe oryzae, which destroys enough rice to feed around 200 million people every year. Rice and the rice blast fungus are involved in a co-evolutionary arms race, fighting for the upper hand. As the fungus relies on effector proteins to help it infect and reproduce within rice plants, rice has evolved immune receptors that allow it to detect and prevent the spread of the fungus. However, the rice blast fungus has evolved stealthy effector proteins that remain undetected by the rice immune system but can still promote disease. In work recently published in the Journal of Biological Chemistry, an international team of scientists has investigated how one stealthy effector protein might maintain its disease-promoting activity but evade immune detection. This research has an ultimate aim of engineering a receptor that would allow rice plants to better defend themselves. 

A pain in the paddy field

We’re familiar with images of the rice paddies of Asia, but this impressive sight represents an irresistible target for the rice blast fungus, Magnaporthe oryzae. Unable to run away from pests and pathogens, plants have evolved immune systems to detect and defend against attack. However, huge swathes planted with the same variety creates an evolutionary pressure for pests and pathogens; a feast is at hand if they can evade those defences. 

One way that pathogens try and gain an advantage is through the use of effector proteins. These proteins can suppress the plant’s immune system and manipulate the plant’s own systems to help the pathogen infect and replicate. However, the mechanisms they employ to do so are not fully understood.  

In collaboration with scientists from Japan and Thailand, researchers at the UK’s John Innes Centre and The Sainsbury Laboratory have been investigating the interaction between rice plants and the rice blast fungus, with the ultimate goal of engineering new genetic resources that will help rice fight this damaging disease.

Read more on the Diamond website

Image: Rice fields in Asia

A novel approach offers hope for an HCV vaccine

An HCV vaccine is needed, but hard to develop. A structural mimic may be the key to enhancing our immune response

Globally, more than 70 million people were struggling with a chronic hepatitis C virus (HCV) infection in 2015. Although effective drugs are available to treat chronic infections, only 13% of cases received curative treatment. The fact that only 20% have been diagnosed is of even greater concern. Although a minority of newly-infected individuals (10–40%) manage to overcome the disease, most develop a chronic infection. Most acute cases of HCV are asymptomatic, leading to undetected virus transmission. Left untreated chronic HCV can lead to serious liver damage and an increased risk of liver cancer. As curative therapies alone cannot eliminate the virus, a vaccine is required. However, because HCV is very diverse and evolves rapidly to evade the immune system, developing an effective vaccine is challenging. In work recently published in npj Vaccines, scientists from the MRC-University of Glasgow Centre for Virus Research, the University of St. Andrews and Imperial College London describe an alternative strategy that uses a structural mimic to encourage the immune system to make antibodies that can recognise multiple strains of the virus i.e. broadly-neutralising antibodies (bNAbs) against HCV. 

A moving target

With its high genetic diversity and an envelope of ever-changing glycoproteins, HCV is challenging for the human immune system to detect and counteract. The minority of cases in which the virus is successfully cleared from the body show a broad, strong T-cell response and neutralising antibodies during the early phase of infection. Individuals who have previously cleared an HCV infection have an 80% chance of successfully fighting off reinfection, indicating that a protective immune response has been induced and that vaccination is a realistic goal. However, with seven distinct genotypes and more than 60 subtypes, the genetic variation makes it challenging to produce a vaccine that would protect against all infections. 

Read more on the Diamond website

Image: I03 beamline at Diamond

Credit: Diamond Light Source

Understanding what makes COVID-19 more infectious than SARS

Australian and International researchers continue to have rapid access to the macromolecular and microfocus beamlines at the Australian Synchrotron to solve protein structures in the fight against COVID-19.

“Since coming out of a hard lockdown, we are now accepting proposals for other research,” said Principal Scientist Dr Alan Riboldi-Tunnicliffe.

“Because scientists can access the beamline remotely, they do not have to worry about changes to borders and travel restrictions.”

There have been a number of COVID-19 publications, which included structural information about key proteins in the virus, from the beamlines.

Instrument scientist Dr Eleanor Campbell reports that an international team of researchers led by the University of Bristol (UK) have identified a possible cause of SARS-CoV-2’s increased infectivity compared to SARS-CoV (the virus which emerged in China in 2003) , which could provide a target for developing COVID-19 therapies.

Australian collaborators included researchers from the Institute of Molecular Bioscience at the University of Queensland, who sent the samples to the Australian Synchrotron.

Read more on the Australian Synchrotron website

Scientists discover potential method to starve the bacteria that cause Tuberculosis

By deepening our understanding of how Tuberculosis bacteria feed themselves, University of Guelph researchers have identified a potential target for drug treatment. The team used the Canadian Light Source (CLS) at the University of Saskatchewan to image the bacteria in fine detail.

The infectious disease Tuberculosis (TB) is one of the leading causes of death worldwide. While rates of TB in Canada have remained relatively static since the 1980s, the disease disproportionately affects Indigenous populations. With TB-causing bacteria becoming increasingly resistant to antibiotics, researchers and drug makers are eager to find new, more effective treatments.

Researchers have known for some time that the bacteria that causes TB (Mycobacterium tuberculosis) uses our body’s cholesterol – a steroid – as a food source. Other relatives of the bacteria that do not cause disease share its ability to break down steroids. In this study, the University of Guelph team identified the structure of an enzyme (acyl CoA dehydrogenase) involved in steroid degradation in another member of the same bacteria family, called Thermomonospora curvata.

Read more on the CLS Website

Image: This rendering shows the shape of a tunnel (orange) where the substrate binds. Any drugs targeting this enzyme would need to fit to this pocket.

“foot-2-foot” interaction sheds light on bacterial conjugation

Bacteria possess mechanisms to establish communication between cells. This is especially important in bacterial conjugation, a process that allows bacteria to share genetic material. This is often used by bacteria to transfer antibiotic resistance genes and other virulence factors to neighbor cells, increasing the antibiotic resistance spread.

Now, a research team of ALBA scientists report the structural mechanism by which two proteins, Rap and Rco, act together to regulate conjugation. Rco is a repressor of conjugation, whereas Rap binds Rco and prevents Rco-mediated conjugation repression, thus resulting in an activation of the conjugation mechanism. The main results of the study show that Rap contains a binding pocket were a short peptide can bind, producing structural changes in Rap that forces its tetramerization, releasing Rco for blocking conjugation. Tetramerization occurs through an interaction that scientists named “foot-2-foot”, which differs significantly from the model proposed for other proteins of the Rap family.

Read more on the ALBA website

Image: RappLS20 tetramerization, side view of the peptide-bound tetramer. The red arrows indicate the loops connecting helices H4 and H5. (C) Zoom of the area around the N-terminus of helix H4, showing the insertion of this helix into the opposite monomer. The homotetramerization caused by the foot-2-foot interactions of the NTDs of RappLS20 provides an explanation for the activation of the RcopLS20 partner. In the absence of the peptide, the NTDs are positioned such that they allow the interaction with RcopLS20. However, upon binding the signaling peptide, the NTDs shift outwards, facilitating the formation of the homotetramer, leading to a change of the interaction surface of the NTDs that is no longer available for interactions with RcopLS20

Effective new target for breast cancer treatment

An international study led by scientists at the University of Sussex has provided strong evidence for an effective new target for breast cancer treatment. The five-year study, called “The structure-function relationship of oncogenic LMTK3” published in Science Advances, involved researchers from seven institutions across three countries including Diamond. 

The study suggests that LMTK3 inhibitors could be effectively used for the treatment of breast cancer, and potentially other types of cancer. The structure of oncogenic LMTK3 (Lemur Tyrosine Kinase 3 ) determines its role and functions allowing drug inhibition as a new therapeutic strategy.

It is hoped the research will allow the further development and optimisation of LMTK3 inhibitors as a new type of orally-administered anticancer drug for patients and have potential value not only for breast cancer patients but also for lung, stomach, thyroid and bladder cancer patients.

Read more on the Diamond Light Source website

Image: Crystal structure of LMTK3
Credit: University of Sussex