Archive for the ‘plant viruses’ Category
That’s right: a new header graphic after lo, these many years.
Something old: Maize streak virus, in all its geminate glory, on the left. Picture taken by RG (Bob) Milne in Cape Town, 1978.
Something new: unidentified phycodnaviruses, middle right. Picture by Hendrik Els, 2015.
Something borrowed: T4-like phage particles, right. Picture by Mohammed Jaffer, 2005.
Something blue: Bluetongue orbivirus particles, centre left. Picture by Ayesha Mohamed, 2015.
REGISTRATION IS NOW OPEN – VIROLOGY AFRICA 2015
On behalf of the Institute of Infectious Disease and Molecular Medicine of the University of Cape Town and the Poliomyelitis Research Foundation, we are pleased to invite you to Virology Africa 2015 at the Cape Town Waterfront.
VENUE AND DATES:
The conference will run from Tuesday 1st – Thursday 3rd December 2015. The conference venue is the Radisson Blu Hotel with a magnificent view of the ocean. The hotel school next door will host the cocktail party on the Monday night 30th November and in keeping with Virology Africa tradition, the dinner venue is the Two Oceans Aquarium.
Early Bird Registration closes – 30 September 2015
Abstract Submissions deadline – 30 September 2015
The ACADEMIC PROGRAMME will include plenary-type presentations from internationally recognised speakers. We wish to emphasise that this is intended as a general virology conference – which means we will welcome plant, human, animal and bacterial virology contributions. The venue will allow for parallel workshops of oral presentations. There will also be poster sessions. Senior students will be encouraged to present their research. We have sponsorship for students to attend the meeting and details will be announced later in the year.
A program outline has been added to the website
Our preliminary programme includes two workshops.
There is a hands-on workshop on “Plant cell packs for transient expression: Innovating the field of molecular biopharming”, with the contact person being Dr Inga Hitzeroth – Inga.Hitzeroth@uct.ac.za. This workshop will run at UCT one day before the conference, 30th November, and a second day, 4th December, after the conference.
The second workshop is on “”Viromics for virus discovery and viral community analysis”. The workshop at UCT will be on 4 and 5 December with the contact person being Dr Tracy Meiring – firstname.lastname@example.org.
Some of the workshop presenters will be integrated into the conference programme but the practical components will be run at University of Cape Town. Separate applications are necessary for each workshop.
If you are prepared to fund an internationally recognised scientist to speak at the conference or if you wish to organise a specialist workshop as part of the conference, please contact
Anna-Lise Williamson or Ed Rybicki.
For any enquiries please contact
Miss Bridget Petersen/ Email: email@example.com or phone: +27 21 486 9111
Ms Deborah McTeer/Email: firstname.lastname@example.org or +27 83 457 1975
I would like to test the response to a Introduction to Virology ebook that I want to develop from my extant Web-based material, given that this is likely to disappear soon with our Web renewal project here at UCT.
Download the Virus Picture Book excerpt here. And then please tell me what you think / whether you would buy one (projected price US$15 – 20)? Ta!
We saw last week how sulphur dioxide released from the Laki fissure system accounted for many deaths due to poisoning. We will stay with poisons this week as well, for virus has its roots in the Latin term for “poison”
Sourced through Scoop.it from: www.thehindu.com
Nice article – and from a newspaper in India, no less! Adds to the history of virology in a very accessible way.
The history of maize streak virus research is generally taken as starting in 1901, with the publication of the
by “Claude Fuller, Entomologist”. However, in the Report he does make reference to articles in the “Agricultural Journal” for August 3rd and 31st, 1900, and quotes personal sources as having noticed the disease of “mealie variegation” as early as the 1870s. He comments that:
“…mealie growers…have been acquainted with variegated mealies…for at least 20 years…”, and “…Thomas Kirkman…has known the disorder for 30 years past…”.
His conclusions, although carefully arrived at, were very wrong. Fuller claimed the disease was due to soil deficiency or a “chemical enzyme” in soils, and could be combatted by intensive cultivation and “chemical manures”. However, his carefully-written account is still of great historical interest, and the observations are valuable as they are objective accounts of a skilled scientist. The records of streaked grasses in particular are useful, as we still collect such samples to this day. Fuller was later sadly a victim of one the first traffic accidents in what was then Lourenco Marques in Mozambique.
The disease – now known as maize streak disease (MSD) – occurs only in Africa and adjacent Indian Ocean islands, where it is one of the worst occurring in maize. The causal agent was discovered to be a virus by HH Storey in 1932, who termed it maize streak virus (MSV). The virus was found to be obligately transmitted by the leafhopper Cicadulina mbila, also by Storey, in 1928. In 1978, MSV was designated the type virus of the newly described group taxon Geminivirus.
Early studies indicated that there were several distinctly different African streak viruses adapted to different host ranges (Storey & McClean, 1930; McClean, 1947). These studies were based on the transmission of virus isolates between different host species and symptomatology.
In a subsequent study of streak virus transmission between maize, sugarcane, and Panicum maximum, the relatively new technique of immunodiffusion was employed, using antiserum to the maize isolate. From the results it was concluded that the maize, sugarcane, and Panicum isolates were strains of the same virus, MSV (Bock et al., 1974). The maize isolate was given as the type strain. The virus was only properly physically characterised in 1974, when the characteristic geminate or doubled particles were first seen by electron microscopy, and only found to be a single-stranded circular DNA virus in 1977 (Harrison et al., 1977).
The first isolates of MSV were sequenced in 1984 (Kenya, S Howell, 1984; Nigeria, P Mullineaux et al., 1984), and the virus was found to have a single component of single-stranded circular DNA (sscDNA), and to be about 2700 bases in size. The two isolates were about 98% identical in sequence. The second team took delight in noting that the first sequence was in fact of the complementary and not the virion strand.
A major advance in the field occurred in 1987, when Nigel Grimsley et al. showed that a tandem dimer clone of MSV-N in an Agrobacterium tumefaciens Ti plasmid-derived cloning vector, was infectious when the bacterium was injected into maize seedlings. Subsequently, Sondra Lazarowitz (1988) obtained the sequence of an infectious clone of a South African isolate (from Potchefstroom) – MSV-SA – and showed that it also shared about 98% identity with the first two sequences.
Since the early days other transmission tests and more sophisticated serological assays were performed on a wide range of streak isolates from different hosts and locales, and it was claimed that all forms of streak disease in the Gramineae in Africa were caused by strains of the same virus, MSV. This view changed as more and more viruses were characterised, however, and it became obvious that there were distinctly separate groupings of viruses that constituted different species: these were sugarcane streak viruses (SSV, see Hughes et al., 1993), the panicum streak viruses (PanSV, see Briddon et al., 1992), and the maize streak viruses. Together these viruses constituted an African streak virus group (see Hughes et al., 1992; Rybicki and Hughes, 1990), distinct from an Australasian striate mosaic virus group, and other more distantly related viruses (see here for the state of the art in 1997). These studies together with a later one by Rybicki et al. in 1998 also pointed up the utility of the polymerase chain reaction (PCR) for amplification, detection and subsequent sequencing of DNA from diverse mastreviruses.
A more modern and comprehensive account can also be found here, in a recent review written for Molecular Plant Pathology.
Dear ViroBlogy and Virology News followers:
Anna-Lise Williamson and I plan to have another in our irregular series of “Virology Africa” conferences in November-December 2015, in Cape Town.
As previously, the conference will run over 3 days or so, possibly with associated workshops, and while the venue is not decided, we would like to base it at least partially in the Victoria & Alfred Waterfront.
We also intend to cover the whole spectrum of virology, from human through animal to plant; clinical aspects and biotechnology.
We intend to make it as cheap as possible so that students can come. We will also not be inviting a slate of international speakers, as we have found that we always get quite an impressive slate without having to fund them fully.
It is also the intention to have a Plant Molecular Farming workshop – concentrating on plant-made vaccines – concurrently with the conference, in order to leverage existing bilateral travel grants with international partners. If anyone else has such grants that could be similarly leveraged, it would be greatly appreciated.
See you in Cape Town in 2015!
Ed + Anna-Lise
African cassava mosaic virus (ACMV) in the geminivirus family has being affected 500 million people worldwide by devastating cassava crops during the past decades. It has caused severe symptoms and reduced yield up to the complete loss of roots, the main starchy food source especially for subsistence farmers in Africa. How can a tiny virus with a small genome evoke such dramatic effects? The viral key component, the replication-initiator protein (Rep), forces differentiated plant cells in the phloem to reactivate DNA synthesis. Even more, it does the same in model cells of fission yeast. We have identified, now, a potential cyclin interaction motif, RXL, in the sequence of ACMV Rep, which may be important for cell cycle control. This motif is essential to induce rereplication in yeast and necessary for viral infection of plants.
I am a sucker for geminiviruses and their replication – as can be seen in the pages published here and elsewhere over the years. It is fascinating to me that a small protein like Rep – only ~30 kDa – can do so many things, and especially interfere in such a fundamental way with organised, differentiated cells.
What is even more interesting is that it can do it in such a wide variety of systems: it’s been shown that ACMV can replicate in maize protoplasts as well as in the dicotyledonous cassava; it can evidently function well in yeast as well – and via a pathway that no-one suspected before now.
Truly, a protein of many parts! Congratulations to Katharina Hipp and to my old friends Bruno and Holger.
I have to confess to a guilty secret: there is a pleasure-inducing activity I have been indulging in for a week at a time these past three years.
And not alone….
This consists of going to the Gobabeb Research & Training Centre in the Namib Desert as part of an international “scientific expedition” aimed at investigating microbial soil biodiversity in the sandy and stony desert round Gobabeb. These were started by Professor Don Cowan when he was at the University of the Western Cape, and have fortunately continued now that he has moved to a new Institute at the University of Pretoria.
I put the scientific expedition in quotes because anything that much fun shouldn’t be called scientific, but hey, it’s already resulted in one major paper on hypolith-associated viruses that I’m a minor author on, another co-authored opinion piece in the South African Journal of Science on biodiversity assessment that got the cover, as well as me being invited to be part of the Gobabeb station’s Microbiology & Fungi research “Theme Group“.
Moreover, I am now on the Board of the Institute for Microbial Biotechnology and Metagenomics at UWC on the strength of working with Marla Trindade and Lonnie van Zyl and others on scraping bits of green stuff off rocks and then watching them ultrafilter washings of it – so I suppose that we really did do some science, even if it was sinfully enjoyable. In any case, something that happened last year took me back to my roots – as well as possibly getting me some street (or gully) cred with the biodiversity crowd.
Basically, there we were in the Welwitschia-rich gullies near Homeb, 11 km from Gobabeb, visiting said plants. There had been some rain 3 weeks previously, apparently, and there was an amazing eruption of foliage from some kind of bulb, every plant the same age and every one frantically flowering for all they were worth. This alone was noteworthy, as the gullies were completely devoid of any trace of such plants the previous year. As we were wandering about, looking at Welwitschias, one Olivier Zablocki from the Univ Pretoria team – who had just done a MSc in plant virology with Gerhard Pietersen at UP – said something along the lines of “I wonder if there are any viruses infecting these plants?”.
“What, like that one?” I said, having just fortuitously noticed a plant with tell-tale streaks on its leaves. Of course, I seem to have lost my photos – temporarily, I hope! – after a Mac Mini OSX update disaster, but Olivier was kind enough to provide the necessary:
This sparked a flurry of activity, with people being called to observe the plant, and going out and looking for more.
Which were not found: not one other plant, of the hundreds we saw there and nearer Homeb, had any streaks at all. What is more, they were growing all up and down some of the more inhospitable gravelly and rocky slopes I have ever seen, meaning they had to be seriously drought-tolerant, given the unlikelihood of them ever being exposed to much water. This meant they must be ephemeral, or putting out foliage and flowers only after rain – and I have never seen anything flower as fast; three days later they were already fruiting.
We made the collective decision that this was sufficiently scientifically interesting to warrant its collection, and the plant was carefully dug up – with difficulty; the onion-like bulb was deep and seriously embedded among rocks – and carefully transported back to Gobabeb, hopefully for identification and then packaging to be taken back to Pretoria.
And yes, we did have a permit!
Meaning the foliage could go back to Pretoria, and there be subjected by Olivier to electron microscopy, and then RNA isolation and cDNA synthesis. And lo, it came to pass – that a new potyvirus was discovered. Kudos, Olivier and the Cowan lab! The ms is submitted, and we wait only for…well, acceptance would be nice, but the proof is in the sequence. And the pictures – murky EMs done by Olivier from precious tissue extracts, to boot.
And it took an old plant virologist to find it. Life in the greying dog yet!
…and now it’s published – as a Disease Note in Plant Disease. Thanks Evelien!
RNA interference (RNAi) is a powerful approach for elucidating gene functions in a variety of organisms, including phytopathogenic fungi. In such fungi, RNAi has been induced by expressing hairpin RNAs delivered through plasmids, sequences integrated in fungal or plant genomes, or by RNAi generated in planta by a plant virus infection. All these approaches have some drawbacks ranging from instability of hairpin constructs in fungal cells to difficulties in preparing and handling transgenic plants to silence homologous sequences in fungi grown on these plants.
Here we show that RNAi can be expressed in the phytopathogenic fungus Colletotrichum acutatum (strain C71) by virus-induced gene silencing (VIGS) without a plant intermediate, but by using the direct infection of a recombinant virus vector based on the plant virus, tobacco mosaic virus (TMV). We provide evidence that a wild-type isolate of TMV is able to enter C71 cells grown in liquid medium, replicate, and persist therein. With a similar approach, a recombinant TMV vector carrying a gene for the ectopic expression of the green fluorescent protein (GFP) induced the stable silencing of the GFP in the C. acutatumtransformant line 10 expressing GFP derived from C71.
The TMV-based vector also enabled C. acutatum to transiently express exogenous GFP up to six subcultures and for at least 2 mo after infection, without the need to develop transformation technology. With these characteristics, we anticipate this approach will find wider application as a tool in functional genomics of filamentous fungi.
TMV graphic from Russell Kightley Media
This is a nice paper for two main reasons: one, they were able to get VIGS – virus-induced gene silencing – working in a non-model fungus; two, they did it with TMV.
TMV! A plant virus in good standing, not previously shown to infect fungi productively, even if it has been studied in yeast as far as replication requirements go.
This is very interesting, not the least because it opens up the possibility that TMV NATURALLY infects some soil / leaf surface fungi.
Which could open up some investigation of just how the virus gets around, because it has always been touted as being only “mechanically” transmissible – even though we and others have shown it CAN be transmitted by aphids (reasonably inefficiently).
Mind you, Barbara von Wechmar and others in our lab showed in the 1980s that wheat stem and leaf rust fungi could transmit Brome mosaic virus and that Puccinia sorghi could transmit a potyvirus; they just did not have the techniques to look at whether or not it replicated too.
As far as my last post here is concerned, I think there is going to be a LOT of stuff coming out in the next few years on how “plant” and “insect” and “fungal” viruses are in fact considerably more promiscuous in choice of host(s) than we have hitherto been aware.
Now, just to prove what Barbara always said, that Tobacco necrosis virus is also a bacteriophage….
Thanks to Gary Foster (@Prof_GD_Foster) for pointing this out!
See on m.pnas.org