How Viruses Attack Plants

Viruses are incapable of reproducing without the help of a host, whose cells copy their genetic material and fabricate the building blocks of new virus particles.

By Claire Asher | February 1, 2018

Most plant viruses are transmitted by insect vectors that cause damage to the plant and create an entry point for pathogens, or that tap into the phloem to feed. Once inside, viruses use the handful of genes in their tiny genomes to orchestrate the plant cells’ machinery, while evading the plant’s defenses. Below is a generalized depiction of this infection process for RNA viruses, the most common type of plant virus.

© PENS AND BEETLES STUDIOS

1. Some viruses can infect plants when aphids and other insects tap into the phloem to feed. Such insect vectors can also pick up virus particles and carry them to new plant hosts.
2. Other viruses infect plant cells through a wound site created by a leaf-munching insect such as a beetle.

© PENS AND BEETLES STUDIOS

1. Viral capsid shell opens to release the viral genome, which is translated into proteins that direct the formation of a viral factory from membranes of the endoplasmic reticulum and other organelles.
2. Antiviral proteins, such as those in the Argonaute family, patrol cells for invading pathogens, but they cannot break into the viral factories.
3. Viral RNA is replicated and exported to the cytoplasm.
4. Viral RNA and newly assembled viral particles move to other cells through plasmodesmata, which can be widened by virus-encoded movement proteins.
5. Some virus particles enter the plant’s transport streams.

------------------

This article infographic on virus attack on plants is also relevant to turf grasses.  There are quite a few virus diseases of relevance to turf, and this article offers some information on what happens with a generic infection, although some other pathways are also possible.

The article was first published in the online edition of The Scientist, late February 2018.

See - https://www.the-scientist.com/?articles.view/articleNo/51433/title/How-Viruses-Attack-Plants/&articles.view/articleNo/51433/title/How-Viruses-Attack-Plants&utm_campaign=TS_DAILY%20NEWSLETTER_2018&utm_source=hs_email&utm_medium=email&utm_content=60971361&_hsenc=p2ANqtz-8sRnFpf4PSVKhS4qCRqjpdE3cVxZ1X-9R7OqOnFcESv0ja5HFtMrFtLS0dq84GAgWhL76mls4oPJVH6tAS1ENFvd0ibsCrEhHoAA3AZacEjPsaOEY&_hsmi=60971361

‘Gene-silencing’ technique - game-changer for crop protection?

Researchers at the University of Surrey and University of Queensland have developed a revolutionary new crop protection technique which offers an environmentally-friendly alternative to genetically-modified crops and chemical pesticides.

The breakthrough research, published in Nature Plants, could have huge benefits for agriculture and positively impact communities around the world. Plant pests and pathogens are estimated to reduce global crop yields by 30 to 40 per cent a year, constraining global food security. At the same time, the need for higher production, regulatory demands, pesticide resistance, and concern about global warming driving the spread of disease all mean there is a growing need for new approaches to crop protection.

The researchers have found that by combining clay nanoparticles with designer ‘RNAs’ (molecules with essential roles in gene biology), it is possible to silence certain genes within plants. The spray they have developed – known as BioClay – has been shown to give plants virus protection for at least 20 days following a single application. When sprayed with BioClay, the plant ‘thinks’ it is being attacked by a disease or pest insect and responds by protecting itself.  With virus diseases commonplace in many field crop and vegetable crops, this could be a huge breakthrough - essentially immunising plants when a disease threatens.

The latest research overcomes the instability of ‘naked’ RNAs sprayed on plants, which has previously prevented them from being used effectively for virus protection. By loading the agents on to clay nanoparticles, they do not wash off, enabling them to be released over an extended period of time before degrading.

The BioClay technology, which is based on nanoparticles used in the development of human drug treatments, has a number of advantages over existing chemical-based pesticides. Since BioClay is non-toxic and degradable, there is less risk to the environment and human health. It can also be used in a highly targeted way to protect crops against specific pathogens.

Professor G.Q. Max Lu, President and Vice-Chancellor of the University of Surrey and co-author of the research paper, said: “This is one of the best examples of nanoparticles being effective for biological molecular delivery with a controlled release rate for combating diseases in plants or animals. The same nanoparticle technology invented and patented in my laboratory at the University of Queensland was used for effective targeted drug delivery. It was licensed to an Oxford-based pharmaceutical company and is now being commercialised for drug development.”

“I am very pleased to see the exciting results of this project and the publication of our research in the prestigious Nature Plants journal.”

The research paper, ‘Clay nanosheets for stable delivery of RNA interference as a topical application to protect plants against viruses’ is published in Nature Plants on 10 January 2017.

The research was led by researchers Professor Neena Mitter and Professor Gordon Xu at the University of Queensland in collaboration with Professor Lu of the University of Surrey. 

While field trials been conducted successfully, a lot more field and lab research will be needed to reach the goal of regulatory approvals and have the technique used widely. 

More at http://www.fatcow.com.au/articles/news/gene-silencing-technique-is-a-game-changer-for-crop-protection-n2526805#MdQxQZIhvP18Vgci.99