Question from E.D. Ammar on Research Gate

Hi. Does anyone know what happens to the salivary sheaths of hemipteran insects in the host plant with time? Do they stay there indefinitely or do they disappear; when and how? I’d appreciate any answers or references to this topic. Thanks.
What happens to the salivary sheaths of hemipteran insects in the host plant with time?.

If anyone has a clue…. I’ll communicate the answer to Desouky, or perhaps he follows the blog ?




Application of RNAi-based methods to aphid vectors

Michaël Mulot, PhD student, UMR 1131 INRA–Univ. Strasbourg, Santé de la Vigne et Qualité du Vin, Equipe Virologie & Vection, F 68000 Colmar, France.

The genomes of several aphid species are now available, providing a tremendous opportunity to identify genes that have vital functions or are involved in the transmission of viruses. In this purpose, strategies based on RNA interference (RNAi) have been developed for aphids. RNAi is based on the detection of double-stranded RNA (dsRNA) and small interfering RNA (siRNA) molecules by insect cells. This detection can activate the degradation of the messenger RNAs of complementary sequences in the insect cells and thus inhibit the expression of the target gene. Various methods have already been employed to deliver such double-stranded RNA molecules in aphids, but no study comparing the efficacy of these methods was available until now.

In a recent study (Mulot et al., Viruses 2016, 8, 316, doi: 10.3390/v8110316), various methods based on the oral acquisition of double-stranded RNA molecules were used in the aphid vector Myzus persicae. Two genes expressed at different levels in the aphid were selected to conduct this study. This study is the first in which several RNAi methods have been evaluated in a single laboratory using the same genes, the same aphid clone, and the same evaluation criteria for RNAi efficacy, eliminating by this way a number of variation sources in the results. In addition, all methods targeted the same region of each gene under study. These comparative experiments showed (1) that the efficiency of RNAi may differ considerably depending on the target gene, and (2) that intestinal cells of the aphid appear to be preferentially affected by the mechanism of RNAi after oral acquisition of dsRNA. In addition, the use of plants infected with a recombinant Tobacco rattle virus (TRV, a plant virus which forms dsRNA-like replication intermediates) proved to be a promising method for inhibiting the expression of aphid genes, since it has many practical advantages compared to other approaches. This work stresses the need to continue developing innovative strategies to effectively inhibit the expression of aphid genes, e.g. those involved in virus transmission.

A nice review on plant virus vectors by Dietzgen et al. (2016)

Over the last few years, a number of very useful review papers on phytovirus transmission by insects and other vectors have been published, including the chapters in the recent book edited by J.K. Brown at APS Press (previously announced on this blog),  each review putting emphasis on various facets of the domain.

The review by Dietzgen et al. (2016) featured here is also very interesting, as it summarizes the most recent findings at the very cutting edge of research.  It contains a ref list of 177 items.  Moreover, it focusses on the parallels drawn between plant and animal virus vectors, leading the authors to discuss how the knowledge gained with animal virus vectors can stimulate the thoughts on the side of plant virus vectors, and opens new avenues towards better understanding the complex phytovirus–vector interactions at the cellular and molecular levels.  Finally, the review discusses the great potential of novel approaches, such as “omics” and symbiosis biology, in our favorite field of research.

Ralf G. Dietzgen, Krin S. Mann and Karyn N. Johnson
Plant Virus–Insect Vector Interactions: Current and Potential Future Research Directions.
Viruses 2016, 8 (11), 303; doi:10.3390/v8110303

PS  Other vector-related papers in the same journal: here.

Etienne Herrbach
INRA Colmar, France

Similarities to academia?

There is plenty of material available about the problems of evaluating science and scientists based on quantitative measures such as the impact factor of journals (and other measurements). In addition, there are more and more examples of individuals being interviewed for positions, or being promoted, using ‘achievements’ such as a TED talk or having a paper covered by WIRED magazine, as evidence that their work is good. There are many other examples of what I consider a distortion of how to evaluate science and the scientific literature. There is a lot of what I would call PR (public relations) in science today, just as there is in politics or whatever else. Maybe some of it is driven by the lack of funds, or twitter, but the fact is that things are done differently today.

Anyway, yesterday I read a piece in Vanity Fair that I thought was very interesting. The story is worth reading as it illustrates a bit how some of the biotech industry operates. But I cannot avoid thinking of parallels with my own professional life/experience.


RNAseq and B-side results

Phytoplasmas interact with their insect vectors in a very intimate way [1]. In order to deepen this relationship, with many unknown aspects, we performed an RNA seq project on the leafhopper Euscelidius variegatus, which is a well-known natural vector of aster yellows phytoplasmas, including chrysanthemum yellows phytoplasma (CY) and an efficient laboratory vector of Flavescence dorée phytoplasma (FD), as already mentioned in a previous post, see Phytoplasma and their vectors: more than just data flirting.
The RNAseq project originally aimed at investigating the interactions between the insect and the two phytoplasmas, exploiting the fact that the same species could transmit two phylogenetically distant phytoplasmas (competition of the two phytoplasmas in E. variegatus has also been investigated [2]). Main purposes were to provide clues on the insect response to phytoplasma infection and new insights on the molecular mechanisms used by phytoplasmas during insect colonization. However, valuable additional information about the composition of bacterial and virus population in E. variegatus was also obtained, perfectly in line with a recently discussed topic on this blog, see NGS-derived thought.
Among viruses we focused on a picorna-like virus, because we assembled and obtained a very long contig that probably represents the whole viral genome with a good read coverage. Infection was confirmed by RT-PCR in all the tested insects, so it can be considered endemic in the leafhopper colony. This finding was unexpected as the infection was apparently asymptomatic: insect fitness does not seem to be altered, at least in terms of longevity and prolificity. Although we have no experimental clues yet, the virus could be transmitted either transovarially or by a oro-fecal route, in accordance with the literature on other phylogenetically related arboviruses [3].
Interestingly, the virus was detected in both phytoplasma-exposed and not exposed insects and the cross-talk among plant pathogens, arbovirus and endosymbiont bacteria will be certainly very interesting to explore. In the very distant, but very well studied, case of honeybee colony collapse disorder induced by Varroa destructor and the associated deformed wing virus (DWV), it is worth to know that, in the absence of the parasitic mite V. destructor, DWV infection is asymptomatic and no apparent negative impact on honeybee fitness is reported [4]. A mutualistic symbiosis between V. destructor and DWV has been recently demonstrated [5]: the mite acts as vector of the viral pathogen, whereas DWV modulates the honeybee humoral immune response, facilitating mite feeding and reproduction.
How can vector-associated viruses affect insect behavior, plant pathogen transmission efficiency and, ultimately, plant response to infection when they are co-transmitted with plant pathogens to the plant? This is really a fascinating and largely unexplored field of investigation.

[1] Marcone C., 2014. Molecular Biology and pathogenicity of phytoplasmas. Annals of Applied Biology 165: 199-221
[2] Rashidi M., D’Amelio R., Galetto L., Marzachì C., & Bosco D. 2014. Interactive transmission of two phytoplasmas by the vector insect. Annals of Applied Biology 165: 404-413
[3] Van Oers M. M., 2010. Genomics and biology of Iflaviruses. Insect Virology Caister Academic Press, Norfolk, 231-250
[4] de Miranda J. R. & Genersch E., 2010. Deformed wing virus. Journal of Invertebrate Pathology 103: Supplement, S48-S61
[5] Di Prisco G., Annoscia D., Margiotta M., Ferrara R., Varricchio P., Zanni V., Caprio E., Nazzi F. & Pennacchio F., 2016. A mutualistic symbiosis between a parasitic mite and a pathogenic virus undermines honey bee immunity and health. PNAS 113: 3203-3208

On Enhancing Diversity in STEM, part 2

Way back in December of last year I wrote a post about developing an ethic for enhancing diversity in the STEM fields. In it, I focused on one dimension of the case for enhancing diversity among scientists: that post-positivism in science provides a coherent epistemology and ethic on which to ground diversity work.

Yet there remain a number of other dimensions of the case for diversity in STEM. One more pragmatic is the argument that diversity improves the ability of scientists to solve problems within their research projects. Diverse people bring their different experiences, areas of expertise, and ways of thinking to bear on a set of problems, and this can bring about novel solutions. This idea is convincingly discussed in a recent episode of the highly entertaining podcast Reply All. Although the discussion focuses on the problem of diversity in Silicon Valley tech companies (where the workforce may be even more homogeneous than in many STEM fields), the insights into how diversity can improve problem solving and productivity are highly relevant to academic STEM disciplines as well.

(Note, the first half of the podcast episode is about an obscure area of the “Twitter-sphere”. It’s pretty funny and entertaining but not particularly relevant; skip to the second half if you’re in a hurry. Also note: ironically, the hosts of the podcast completely ignored Rosalind Franklin’s contribution when they touched on the discovery of the structure of DNA. They have a follow-up episode where they atone.)

The story in the podcast made me think about the dynamics in the Almeida lab. We are a disciplinarily diverse lab, with expertise in molecular biology, genomics, plant pathology, entomology, macro-ecology, and modeling. We are also a multinational and multicultural lab.  It’s easy to see how diverse disciplines can improve scientific work, particularly when addressing environmental or agricultural problems. My own work has undoubtedly benefited from working with molecular and micro-biologists in the lab. While it remains less clear how other dimensions of our identities (e.g., nationality, race, class, sexual orientation) could improve our work, the ideas put forward in the Reply All podcast make a convincing case for thinking more broadly about diversity. At the very least, it’s a worthwhile question to consider and pursue.