By Michel Cusson, ESC President
______________________________
For my first blog post, you’d probably expect me to talk about some hot issue pertaining to the ESC. However, I chose otherwise (at least this time) and I’ll save Society-related topics for my “Up Front” column, which you can read in the online version of the Bulletin. Instead, I’d like to introduce you to what I consider the coolest product of insect evolution: the use of symbiotic viruses by parasitic wasps to manipulate the physiology of their caterpillar hosts.
Aleiodes indiscretus wasp parasitizing a gypsy moth caterpillar. Photo by Scott Bauer.
In an unusual twist of evolutionary history, some ichneumonid and braconid parasitoids have “captured” a conventional virus and “domesticated” it so that it can be used to their own advantage in the course of parasitism. The viruses in question, known as polydnaviruses (from poly-DNA-virus, but typically pronounced “polyd-na-virus”), replicate in wasp ovaries where they accumulate in the fluid bathing the eggs, before being injected into the caterpillar during parasitization (egg laying). While the carrier wasp is completely asymptomatic, the infected caterpillar displays AIDS-like symptoms, whereby its ability to mount an immune response against the wasp egg or larva is depressed by the virus. In addition, the virus will often block host metamorphosis, particularly when parasitization takes place late in caterpillar development; this will allow the wasp larva to complete its own development before the host undergoes the traumatic events associated with the larva-to-adult transformation.
But what makes these viruses pathogenic in the caterpillar while being apparently harmless in the wasp, and how could such unusual creatures have evolved? To begin understanding the answers to these questions one first needs to know that polydnavirus genomes are permanently integrated into the chromosomal DNA of the carrier wasps. This means that all individuals within a species known to carry one of these viruses contain the viral DNA within their own genome. Production of the viral particles, however, is confined to females and occurs only in ovaries. There, copies of the integrated form of the viral genome are synthesized and packaged into a proteinacious coat known as the “capsid”. These viral particles are released into the lumen of the oviduct, where they accumulate until injection into the caterpillar host.
What’s going on “behind the scenes”. Image by Michel Cusson and Marlene Laforge.
Once injected, the virus gains access to various host tissues where some of its genes are expressed, leading to the synthesis of viral proteins that do the dirty work, i.e., depress the host immune response and perturb host development. Few, if any, of these virulence genes are expressed in the wasp, which probably explains why the wasp is asymptomatic. While the virus does not replicate in the caterpillar, it is the expression of viral genes that makes it possible for the wasp egg and larva to survive within the host. And successful development of the immature wasp is what ensures transmission of the integrated form of the virus to the next wasp generation.
Whether polydnaviruses are “real” viruses has been a matter of debate for many years. For example, some have argued that, although they look like viruses, they are nothing more than a smart device that the wasps have evolved to transfer host-regulating factors to caterpillars during oviposition. However, it is becoming increasingly clear that polydnaviruses arose from ‘conventional’ viruses.
Recently, a group from France has shown that the proteins that make up the coat of braconid polydnavirus particles are highly similar to those of ‘nudiviruses’1, a group of conventional insect viruses that are capable of integrating their genomes into those of their hosts. So, it appears that the genome of a nudivirus became permanently integrated into the chromosomal DNA of an ancestral braconid, some 100 MYA. Since then, evolution has led to the replacement of the original nudiviral virulence genes by other genes that are usefull to the wasp during parasitism. The wasps may therefore be viewed as having ‘domesticated’ the nudivirus, turning it into a mutualistic virus – a phenomenon fairly unique in the world of viruses. Cool stuff, isn’t it?
____________________________ 1Bezier, A., Annaheim, M., Herbiniere, J., Wetterwald, C., Gyapay, G., Bernard-Samain, S., Wincker, P., Roditi, I., Heller, M., Belghazi, M. & (2009). Polydnaviruses of Braconid Wasps Derive from an Ancestral Nudivirus, Science, 323 (5916) 930. DOI: 10.1126/science.1166788
With an estimated 55,000 species found between Pelee Island and Ellesmere Island and colonizing the forests, streams, mountains and plains from the Atlantic to the Pacific, insects form a major component of Canada’s natural heritage and affect our lives on a daily basis. From pests to pollinators and biting flies to butterflies, our six-legged neighbours have played an important role in the development of our nation.
It should therefore come as no surprise that Canada has a growing society of scientists, naturalists and enthusiasts nearly as diverse as the insects to which they are devoted. With research being performed in every province and territory, Canadian entomologists have long placed a high priority on public engagement, sharing their knowledge and passion for insects through outreach activities, extension documents and student mentoring.
Long-legged fly (Dolichopodidae) by Morgan Jackson
It was only a matter of time until the Entomological Society of Canada leaped into the world of social media, and, with a presence on Facebook and Twitter already firmly established, its with great excitement that we present the ESC Blog!
Our goal with the ESC Blog is to provide a platform for Canadian entomologists and enthusiasts to share and discuss their work, stories and favourite insects with the rest of the world.
What might you expect to find here at the ESC Blog? Here are a few of the things we’ve got lined up so far:
articles and updates from the Entomological Society of Canada Board of Directors, as well as from each of Canada’s provincial/regional insect societies
previews of upcoming issues of the Canadian Entomologist and the Canadian Journal of Arthropod Identification
information about annual societal meetings and other entomological events around Canada
stories from the field or lab, profiles of Canadian entomologists/labs and other personal interest articles
science blogging, highlighting some of the exciting entomological research being done in Canada
photos and profiles of Canadian insects
much, much more!
Of course, this blog depends on you, the reader/contributor. Feel free to chime in with your ideas and opinions in the comment sections, or better yet, submit posts of your own. We want to encourage entomophiles from across the country, professional or amateur, seasoned veteran or newbie student, to submit stories, articles and photos that they’d like to show off to the world.
If you’re interested in contributing to the ESC Blog, check out how you could Become an ESC Blogger for tips and guidelines, and feel free to contact us with ideas or questions (we don’t bite, sting or secrete anything toxic, honest). Also, don’t be surprised if you get an email asking if you’d be interested in sharing your latest publication or field trip with the blog; if you were excited to do the work, others will be just as excited to learn about it!
Avec un nombre d’espèces estimé à plus de 55 000 entre l’île Pelée et Ellesmere, ayant colonisé les forêts, ruisseaux, montagnes et plaines de l’Atlantique au Pacifique, les insectes constituent une composante majeure de l’héritage naturel Canadien et affectent durablement notre vie quotidienne. Des ravageurs aux pollinisateurs, des mouches aux papillons, nos cousins à six pattes ont joué un rôle important dans le développement de notre nation.
M. scutellatus (Cerambycidae), un coléoptère longicorne (Photo: Crystal Ernst)
Il n’est ainsi pas surprenant que le Canada soit doté d’une communauté grandissante de scientifiques, naturalistes et amateurs presque aussi diverse que les insectes auxquels ils sont dévoués. Avec des recherches menées au sein de chaque Province et Territoire, les entomologistes canadiens ont longtemps donné la priorité à l’engagement communautaire, partageant leur savoir et leur passion lors de d’activités de vulgarisation, par la rédaction d’ouvrages de vulgarisation et par le mentorat d’étudiants. Ce n’était qu’une question de temps avant de voir la Société d’Entomologie du Canada se lancer à la conquête des réseaux sociaux. Et, avec sa présence sur Facebook et Twitter fermement établie, c’est avec grand plaisir que nous vous présentons le Blogue de la SEC.
Notre but avec le Blogue de la SEC est de proposer une plateforme où les entomologistes et «entomophiles» pourront partager et discuter de leurs travaux, de leurs histoires et de leurs insectes favoris avec le reste du monde.
Que pourrez-vous trouver sur le Blogue de la SEC ? Voici une liste des thèmes que nous avons réunis pour l’instant :
des articles et nouvelles du Conseil d’Administration de la Société d’Entomologie du Canada et de chaque société d’entomologie provinciale ou régionale
des aperçus des volumes à venir du Canadian Entomologist et du Canadian Journal of Arthropod Identification
des informations sur les réunions annuelles et autres évènements entomologiques au Canada
des récits depuis le terrain ou les laboratoires, des profils d’entomologistes/laboratoires canadiens et autres articles personnels
des billets scientifiques, mettant en lumière certaines des plus intéressantes recherches en entomologie au Canada
des photos et profils d’insectes canadiens
bien plus encore !
Evidemment, ce blogue dépend de vous, lecteur/contributeur. Libre à vous de venir présenter vos idées et opinions dans les commentaires, ou mieux, de soumettre votre propre billet. Nous voulons encourager les entomophiles à travers le pays – qu’ils soient professionnels, amateurs, vétéran expérimenté ou étudiant fraîchement débarqué – à soumettre les histoires, articles et photos. Si vous êtes intéressés à l’idée de contribuer au Blogue de la SEC, consultez les règles générales en haut de page et n’hésitez pas nous contacter avec vos idées ou questions (nous ne mordons pas et nous ne secrétons aucune substance toxique, promis !). De même, ne soyez pas étonnés si vous recevez un email vous demandant si vous seriez intéressé à l’idée parler de votre dernier article ou de votre dernier voyage de terrain sur le blogue. Si vous avez pris plaisir à votre travail, il y a de bonnes chances que d’autres personnes voudront en savoir plus!
Alors restez à l’écoute (et vous abonner au flux RSS), car il ya beaucoup de contenu canadien des insectes venant à votre rencontre ! En attendant, n’oubliez pas de consulter le numéro de Juin du Bulletin de la Société d’Entomologie du Canada, qui est rempli d’articles, nouvelles et autres bizarreries entomologiques.
https://esc-sec.ca/wp-content/uploads/2012/04/cropped-esclogoprint2inch2.jpg155155Morgan Jacksonhttp://esc-sec.ca/wp/wp-content/uploads/2017/01/ESC_logo-300x352.pngMorgan Jackson2012-06-01 01:00:542019-11-14 20:20:38Welcome to the ESC Blog!
Cool Insect Viruses
By Michel Cusson, ESC President
______________________________
For my first blog post, you’d probably expect me to talk about some hot issue pertaining to the ESC. However, I chose otherwise (at least this time) and I’ll save Society-related topics for my “Up Front” column, which you can read in the online version of the Bulletin. Instead, I’d like to introduce you to what I consider the coolest product of insect evolution: the use of symbiotic viruses by parasitic wasps to manipulate the physiology of their caterpillar hosts.
Aleiodes indiscretus wasp parasitizing a gypsy moth caterpillar. Photo by Scott Bauer.
In an unusual twist of evolutionary history, some ichneumonid and braconid parasitoids have “captured” a conventional virus and “domesticated” it so that it can be used to their own advantage in the course of parasitism. The viruses in question, known as polydnaviruses (from poly-DNA-virus, but typically pronounced “polyd-na-virus”), replicate in wasp ovaries where they accumulate in the fluid bathing the eggs, before being injected into the caterpillar during parasitization (egg laying). While the carrier wasp is completely asymptomatic, the infected caterpillar displays AIDS-like symptoms, whereby its ability to mount an immune response against the wasp egg or larva is depressed by the virus. In addition, the virus will often block host metamorphosis, particularly when parasitization takes place late in caterpillar development; this will allow the wasp larva to complete its own development before the host undergoes the traumatic events associated with the larva-to-adult transformation.
But what makes these viruses pathogenic in the caterpillar while being apparently harmless in the wasp, and how could such unusual creatures have evolved? To begin understanding the answers to these questions one first needs to know that polydnavirus genomes are permanently integrated into the chromosomal DNA of the carrier wasps. This means that all individuals within a species known to carry one of these viruses contain the viral DNA within their own genome. Production of the viral particles, however, is confined to females and occurs only in ovaries. There, copies of the integrated form of the viral genome are synthesized and packaged into a proteinacious coat known as the “capsid”. These viral particles are released into the lumen of the oviduct, where they accumulate until injection into the caterpillar host.
What’s going on “behind the scenes”. Image by Michel Cusson and Marlene Laforge.
Once injected, the virus gains access to various host tissues where some of its genes are expressed, leading to the synthesis of viral proteins that do the dirty work, i.e., depress the host immune response and perturb host development. Few, if any, of these virulence genes are expressed in the wasp, which probably explains why the wasp is asymptomatic. While the virus does not replicate in the caterpillar, it is the expression of viral genes that makes it possible for the wasp egg and larva to survive within the host. And successful development of the immature wasp is what ensures transmission of the integrated form of the virus to the next wasp generation.
Whether polydnaviruses are “real” viruses has been a matter of debate for many years. For example, some have argued that, although they look like viruses, they are nothing more than a smart device that the wasps have evolved to transfer host-regulating factors to caterpillars during oviposition. However, it is becoming increasingly clear that polydnaviruses arose from ‘conventional’ viruses.
Recently, a group from France has shown that the proteins that make up the coat of braconid polydnavirus particles are highly similar to those of ‘nudiviruses’1, a group of conventional insect viruses that are capable of integrating their genomes into those of their hosts. So, it appears that the genome of a nudivirus became permanently integrated into the chromosomal DNA of an ancestral braconid, some 100 MYA. Since then, evolution has led to the replacement of the original nudiviral virulence genes by other genes that are usefull to the wasp during parasitism. The wasps may therefore be viewed as having ‘domesticated’ the nudivirus, turning it into a mutualistic virus – a phenomenon fairly unique in the world of viruses. Cool stuff, isn’t it?
____________________________
1Bezier, A., Annaheim, M., Herbiniere, J., Wetterwald, C., Gyapay, G., Bernard-Samain, S., Wincker, P., Roditi, I., Heller, M., Belghazi, M. & (2009). Polydnaviruses of Braconid Wasps Derive from an Ancestral Nudivirus, Science, 323 (5916) 930. DOI: 10.1126/science.1166788
Welcome to the ESC Blog!
It should therefore come as no surprise that Canada has a growing society of scientists, naturalists and enthusiasts nearly as diverse as the insects to which they are devoted. With research being performed in every province and territory, Canadian entomologists have long placed a high priority on public engagement, sharing their knowledge and passion for insects through outreach activities, extension documents and student mentoring.
Long-legged fly (Dolichopodidae) by Morgan Jackson
It was only a matter of time until the Entomological Society of Canada leaped into the world of social media, and, with a presence on Facebook and Twitter already firmly established, its with great excitement that we present the ESC Blog!
Our goal with the ESC Blog is to provide a platform for Canadian entomologists and enthusiasts to share and discuss their work, stories and favourite insects with the rest of the world.
What might you expect to find here at the ESC Blog? Here are a few of the things we’ve got lined up so far:
Of course, this blog depends on you, the reader/contributor. Feel free to chime in with your ideas and opinions in the comment sections, or better yet, submit posts of your own. We want to encourage entomophiles from across the country, professional or amateur, seasoned veteran or newbie student, to submit stories, articles and photos that they’d like to show off to the world.
If you’re interested in contributing to the ESC Blog, check out how you could Become an ESC Blogger for tips and guidelines, and feel free to contact us with ideas or questions (we don’t bite, sting or secrete anything toxic, honest). Also, don’t be surprised if you get an email asking if you’d be interested in sharing your latest publication or field trip with the blog; if you were excited to do the work, others will be just as excited to learn about it!
So stay tuned (and subscribe to the RSS feed), because there’s plenty of Canadian insect content coming your way! In the meantime, be sure to check out the June issue of the Bulletin of the Entomological Society of Canada, which is filled with articles, news and other entomological oddities.
———————————————————————-
Avec un nombre d’espèces estimé à plus de 55 000 entre l’île Pelée et Ellesmere, ayant colonisé les forêts, ruisseaux, montagnes et plaines de l’Atlantique au Pacifique, les insectes constituent une composante majeure de l’héritage naturel Canadien et affectent durablement notre vie quotidienne. Des ravageurs aux pollinisateurs, des mouches aux papillons, nos cousins à six pattes ont joué un rôle important dans le développement de notre nation.
M. scutellatus (Cerambycidae), un coléoptère longicorne (Photo: Crystal Ernst)
Il n’est ainsi pas surprenant que le Canada soit doté d’une communauté grandissante de scientifiques, naturalistes et amateurs presque aussi diverse que les insectes auxquels ils sont dévoués. Avec des recherches menées au sein de chaque Province et Territoire, les entomologistes canadiens ont longtemps donné la priorité à l’engagement communautaire, partageant leur savoir et leur passion lors de d’activités de vulgarisation, par la rédaction d’ouvrages de vulgarisation et par le mentorat d’étudiants. Ce n’était qu’une question de temps avant de voir la Société d’Entomologie du Canada se lancer à la conquête des réseaux sociaux. Et, avec sa présence sur Facebook et Twitter fermement établie, c’est avec grand plaisir que nous vous présentons le Blogue de la SEC.
Notre but avec le Blogue de la SEC est de proposer une plateforme où les entomologistes et «entomophiles» pourront partager et discuter de leurs travaux, de leurs histoires et de leurs insectes favoris avec le reste du monde.
Que pourrez-vous trouver sur le Blogue de la SEC ? Voici une liste des thèmes que nous avons réunis pour l’instant :
Evidemment, ce blogue dépend de vous, lecteur/contributeur. Libre à vous de venir présenter vos idées et opinions dans les commentaires, ou mieux, de soumettre votre propre billet. Nous voulons encourager les entomophiles à travers le pays – qu’ils soient professionnels, amateurs, vétéran expérimenté ou étudiant fraîchement débarqué – à soumettre les histoires, articles et photos. Si vous êtes intéressés à l’idée de contribuer au Blogue de la SEC, consultez les règles générales en haut de page et n’hésitez pas nous contacter avec vos idées ou questions (nous ne mordons pas et nous ne secrétons aucune substance toxique, promis !). De même, ne soyez pas étonnés si vous recevez un email vous demandant si vous seriez intéressé à l’idée parler de votre dernier article ou de votre dernier voyage de terrain sur le blogue. Si vous avez pris plaisir à votre travail, il y a de bonnes chances que d’autres personnes voudront en savoir plus!
Alors restez à l’écoute (et vous abonner au flux RSS), car il ya beaucoup de contenu canadien des insectes venant à votre rencontre ! En attendant, n’oubliez pas de consulter le numéro de Juin du Bulletin de la Société d’Entomologie du Canada, qui est rempli d’articles, nouvelles et autres bizarreries entomologiques.