Tag Archives: virus

Reactions of Nicotiana species to inoculation with begomoviruses

begomovirus Some Nicotiana species are widely used as experimental hosts for plant viruses. Nicotiana species differ in ploidy levels, chromosome numbers and have diverse geographical origins. Thus, these species are useful model systems to investigate virus-host interactions, co-evolution of pathogens and hosts and the effects of ploidy level on virus resistance/susceptibility.

This research studied the responses of seven Nicotiana species to inoculation with Cotton leaf curl Multan virus (CLCuMV), a monopartite begomovirus, and Tomato leaf curl New Delhi virus (ToLCNDV), a bipartite begomovirus, both from the Indian subcontinent. All Nicotiana species supported the replication of both begomoviruses in inoculated leaves. However, only three Nicotiana species, namely N. benthamiana, N. tabacum and N. sylvestris showed symptoms when inoculated with ToLCNDV, while N. benthamiana was the only species that developed leaf curl symptoms when inoculated with CLCuMV. CLCuMV accumulated to detectable levels in N. tabacum, but plants remained asymptomatic. A previously identified mutation of RNA dependent RNA polymerase 1 was shown to be present only in N. benthamiana. The finding is in line with earlier results showing that the susceptibility of this species to a diverse range of plant viruses correlates with a defective RNA silencing-mediated host defense.

The results show that individual Nicotiana species respond differently to inoculation with begomoviruses. The inability of begomoviruses to systemically infect several Nicotiana species is likely due to inhibition of virus movement, rather than replication, and thus provides a novel model to study virus-host interactions in resistant/susceptible hosts.

Reactions of Nicotiana species to inoculation with monopartite and bipartite begomoviruses. Virology Journal 2011, 8: 475 doi:10.1186/1743-422X-8-475

…this month’s most tenuous plant link?

Image: André Karwath/Wikimedia Commons.

Image: André Karwath/Wikimedia Commons.

Warning for the zoophobic: this item is about Caenorhabditis elegans – a free-living, transparent nematode {‘roundworm’ –sometimes known as ‘the Arabidopsis of animal biology’ [that’s Arabidopsis (frequently described as ‘the fruit fly of plant biology’) and fruit fly – Drosophila – which in its turn is occasionally referred to as the ‘maize of zoology’…]}. Enough, already! The point I’m trying to make is that each biological discipline has its own ‘model species’, which its devotees believe will illuminate the whole of biology (or something ambitious and worthy like that). As botanists we are used to stories about Arabidopsis thaliana (thale cress as they are known) – our own general-purpose, all-singing, all-dancing, technicolor, typical flowering plant. Well, in the interests of broadening botanists’ appreciation of non-plant disciplines, I thought it useful to mention the worm-like creature that is serving as a model for many facets of animal biology. However, although generally a good model, C. elegans also poses puzzles. For example, it is known that it could protect itself from viral attack using RNA interference (RNAi), but, since no natural virus capable of infecting C. elegans had ever been described, why does it have innate antiviral defences? Well, seek and ye shall find: lo and behold, Marie-Anne Félix et al. have just described natural viruses that will infect this model nematode (PLoS Biology 9: e1000586; doi:10.1371/journal.pbio.1000586), which should permit identification and study of other host mechanisms that counter viral infection. So, what’s the French… err plant… connection? The viruses were isolated from… an apple in an orchard (near Paris). Which proves the old adage that ‘an apple a day keeps the doctor at play’. From a ‘rotten’ apple to a good one now. Steven Kunkel and colleagues have discovered that ursolic acid (3-b-hydroxy-urs-12-en-28-oic acid, also known as urson, prunol, and malol) reduces muscle atrophy (‘muscle wasting’) and promotes muscle growth in mice (Cell Metabolism 13: 627–638, 2011). Furthermore, ursolic acid (UA) – a pentacyclic triterpene – also reduces fat, blood sugar levels, cholesterol and triglycerides, which led the team to suggest that it may also be useful for treating human metabolic disorders such as diabetes. Intriguingly, delving deeper on the Wikipedia site for the compound one finds that UA ‘has been found to reduce muscle atrophy and to stimulate muscle growth in mice’. Which isn’t to say that the Kunkel et al. paper isn’t news, it‘s just that Wikipedia cites that article for that statement (emphasising how up-to-date Wikipedia can be). More surprisingly, a co-citation for that claim is a Science Daily news item, itself probably based upon a press release about the Cell Metabolism paper. But, and even more surprising, is the statement about large amounts of UA being present in apple peel (hence this Plant Cuttings item), which is attributed to the UK’s Daily Mail, a so-called tabloid newspaper, in its item about… the Kunkel et al. article. It all gets a little circular (which is probably what newspapers ‘evolved’ from in the first place), but is an argument for caution in the use of Wikipedia as a primary source. Not to be outdone, CSIRO Plant Industry (Australia) scientists Ming-Bo Wang and Neil Smith have made a breakthrough in understanding how viruses infect plants. They find that the distinctive yellowing that accompanies infection by Cucumber Mosaic Virus (CMV) is due to a special type of viral particle (a ‘satellite’) ‘slicing a gene that makes chlorophyll’. This work should help us better understand how viruses cause diseases in plants – and potentially in animals and humans (and even model nematodes..?).