Geminiviruses are responsible for diseases affecting crops such as cassava and maize in Africa, cotton in the Indian subcontinent and tomatoes across Europe.
Being able to see its structure in great detail is vital as it could help virologists and molecular biologists better understand the virus life cycle, and develop new ways to stop the spread of these viruses and the diseases they cause.
These viruses are named for their curious shape. Viruses usually have a protective shell of protein, or capsid, that acts to protect their genetic material in the environment. In most viruses, this capsid is roughly spherical, but the geminivirus has a ‘twinned’ capsid formed by two roughly spherical shapes fused together.
The molecular details of how this twinned capsid is achieved – and how it assembles in cells or expands to release the genome and start a new infection – has remained a mystery, despite the risk posed by the virus to agricultural economies worldwide.
"In many other types of virus, the spherical capsids are built from a single protein that adopts three different shapes, which then fit together to form a closed container," explained Professor Neil Ranson, who led the research team at the Astbury Centre.
"But geminivurses are not spherical, so must be using a different set of rules. Using cryo-EM, we’ve been able to show that they do use three different shapes of the same protein, but with a completely different rulebook for assembly."
One of the difficulties in studying geminviruses is growing them in sufficient quantities for structural studies. The team studied a type of geminvirus called ageratum yellow vein virus, which was produced in tobacco plants under carefully controlled conditions by researchers at the John Innes Centre in Norwich.
The team at the John Innes Centre, led by Dr Keith Saunders and Professor George Lomonossoff, also developed a method for assembling geminivirus particles within plants in the absence of infection. This highlighted the role played by the single-stranded DNA in particle formation.
"Having worked for many years to understand the diseases geminiviruses cause, it was very satisfying to apply modern genetic methods to generate these geminate structures," said Dr Saunders. "We’ve now been able to analyse the role that different conformations of the coat protein play in particle assembly, and we can potentially make other viruses and virus-like particles that might otherwise be impossible to isolate from natural infections."
"Using our ‘next generation’ cryo electron microscopy we have modelled the position of the majority of the atoms in the virus", said Dr Emma Hesketh, a postdoctoral researcher in the Astbury Centre, who carried out the work to create the images of the structure.
"This technology is often referred to as the resolution revolution, and it’s enabled us to get this fascinating – and very beautiful – insight into these structures. By using these techniques to understand the structure and the life cycle of these viruses, we can come a step closer to understanding how to interrupt that life cycle, and inhibit the spread of plant disease."
Top image shows an impression of the near-atomic level structure of the geminivirus created by the University of Leeds.
For more information, contact Peter Le Riche, University of Leeds Media Relations Manager, on +44(0)113 343 2049 or email@example.com
The research work was funded by the Biotechnology and Biological Sciences Research Council, part of UK Research and Innovation.
Stephen Muench with Glaxo SmithKline & UCB Celltech, BBSRC Industrial Partnership Award (Apr 2018), £480,225
Steve Clapcote, BBSRC (Apr 2018), £443,072
Helen Miller, Innovate UK (Apr 2018), £999,960
Elisabetta Groppelli, David Rowlands & Stanley Lemon (University of North Carolina), Medical Research Foundation Fellowship (Apr 2018), £293,494
Nikesh Patel, Medical Research Foundation fellowship (Apr 2018), £290,976
Graham Askew with colleagues in Hull and Liverpool, BBSRC (Apr 2018), £150,498
Andrew Macdonald, Neil Ranson & Richard Foster, Kidney Research UK (Apr 2018), £82,821
Jessica Kwok & Ralf Richter, Leverhulme Trust (Apr 2018), £298,273
Julie Aspden, Royal Society (Apr 2018), £20,000
Liz Duncan, Royal Society (Mar 2018), £14,602
Alex O'Neill & Ryan Seipke, BBSRC (Feb 2018), £45,489
Jim Deuchars, Royal Society (Feb 2018), £16,300
Stefan Kepinski & Netta Cohen, Leverhulme Trust (Feb 2018), £320,387
Lisa Collins, BBSRC (Feb 2018), £49,950
Alison Baker, BBSRC (Feb 2018), £30,000
Lars Jeuken, BBSRC (Feb 2018), £30,000
Nikita Gamper, BBSRC (Feb 2018), £30,000
Scott Bowen, Leducq Foundation Grant (Feb 2018), £28,470
Jessica Kwok and Ronaldo Ichiyama, International Spinal Research Trust (Feb 2018), £94,450
Alex O'Neill, Oxford Drug Design (Jan 2018), £86,098
Dave Lewis and Colleagues in South Africa, HEFCE Global Challenge Research (Jan 2018), £48,000
Sarah Calaghan, Ed White, John Colyer, Isuru Jayasinghe, BHF (Jan 2018), £128,308
Christine Foyer and Alison Baker, HEFCE GCRF Grant (Jan 2018), £71,158
Alison Baker, Yun Yung Gong and Lindsay Stringer and ICRISAT India, HEFCE GCRF Grant (Jan 2018), £27,000
Graham Askew, Simon Walker, BBSRC (Jan 2018), £699,781
Jennifer Tomlinson, Royal Society (Jan 2018), £512,801
Alison Dunn, NERC (Dec 2017), £18,000
Jennifer Tomlinson, Royal Society-Research Fellows Enhancement Award (Dec 2017), £94,681
Helen Miller, AB AGri Grant (Dec 2017), £73,600
Simon Walker, Royal Society Enhancement Award (Dec 2017), £10,000
Carrie Ferguson, Bryan Taylor, Harry Rossiter, The Physiological Society (Dec 2017), £7,392
Ralf Richter, Royal Society (Dec 2017), £6,000
Christine Foyer, British Council Newton Fund (Dec 2017), £49,840
Adrian Whitehouse and colleagues in School of Chemistry and University of Liverpool, MRC (Nov 2017), £622,319
Michelle Peckham, Neil Ransom, MRC (Nov 2017), £495,159
Dave Lewis, British Council India (Nov 2017), £22,540
Elton Zeqiraj, Royal Society (Nov 2017), £15,000
Hannah Dugdale, Royal Society (Nov 2017), £15,000
Shaunna Burke, Cancer Research UK Innovation Grant (Nov 2017), £20,000
Alex O'Neill and colleagues in Chemistry, BBSRC (Nov 2017), £431,865
Jessica Kwok, Wings for Life (Nov 2017), £87,365
Tom Bennett, BBSRC (Oct 2017), £523,679
Neil Ranson, Darren Tomlinson, BBSRC (Oct 2017), £494,318
Nikita Gamper, BBSRC (Oct 2017), £490,426
Amanda Bretman and colleagues from UEA, NERC (Oct 2017), £430,886
Juan Fontana, Rosetrees Trust consumables grant (Oct 2017), £22,500
Helen Miller, DSM Nutritional Products AG (Sep 2017), £69,988
Neil Ranson, Juan Fontana, Mark Harris, Michelle Peckham, Ralf Richter, Peter Stockley, Patricija Van Oosten-Hawle and colleagues in Engineering, FMH and MAPS, Wellcome Trust Equipment Call (Sep 2017), £418,000
Jamie Johnston, Physiological Society (Sep 2017), £10,000
Frank Sobott, Adrian Goldman, Mark Harris, Andrew Macdonald, Stephen Muench, Sheena Radford and colleagues in FMH and MAPS, Wellcome Trust Equipment Call (Aug 2017), £415,000