In vitrotranscriptomic analyses of the aphid’s secondary symbiont,Hamiltonella defensa

2016 ◽  
Author(s):  
Germain Chevignon
2017 ◽  
Vol 83 (8) ◽  
Author(s):  
Matthew R. Doremus ◽  
Kerry M. Oliver

ABSTRACT Insects and other animals commonly form symbioses with heritable bacteria, which can exert large influences on host biology and ecology. The pea aphid, Acyrthosiphon pisum, is a model for studying effects of infection with heritable facultative symbionts (HFS), and each of its seven common HFS species has been reported to provide resistance to biotic or abiotic stresses. However, one common HFS, called X-type, rarely occurs as a single infection in field populations and instead typically superinfects individual aphids with Hamiltonella defensa, another HFS that protects aphids against attack by parasitic wasps. Using experimental aphid lines comprised of all possible infection combinations in a uniform aphid genotype, we investigated whether the most common strain of X-type provides any of the established benefits associated with aphid HFS as a single infection or superinfection with H. defensa. We found that X-type does not confer protection to any tested threats, including parasitoid wasps, fungal pathogens, or thermal stress. Instead, component fitness assays identified large costs associated with X-type infection, costs which were ameliorated in superinfected aphids. Together these findings suggest that X-type exploits the aphid/H. defensa mutualism and is maintained primarily as a superinfection by “hitchhiking” via the mutualistic benefits provided by another HFS. Exploitative symbionts potentially restrict the functions and distributions of mutualistic symbioses with effects that extend to other community members. IMPORTANCE Maternally transmitted bacterial symbionts are widespread and can have major impacts on the biology of arthropods, including insects of medical and agricultural importance. Given that host fitness and symbiont fitness are tightly linked, inherited symbionts can spread within host populations by providing beneficial services. Many insects, however, are frequently infected with multiple heritable symbiont species, providing potential alternative routes of symbiont maintenance. Here we show that a common pea aphid symbiont called X-type likely employs an exploitative strategy of hitchhiking off the benefits of a protective symbiont, Hamiltonella. Infection with X-type provides none of the benefits conferred by other aphid symbionts and instead results in large fitness costs, costs lessened by superinfection with Hamiltonella. These findings are corroborated by natural infections in field populations, where X-type is mostly found superinfecting aphids with Hamiltonella. Exploitative symbionts may be common in hosts with communities of heritable symbionts and serve to hasten the breakdown of mutualisms.


2012 ◽  
Vol 105 (3) ◽  
pp. 447-453 ◽  
Author(s):  
Daniel M. Erickson ◽  
Elizabeth A. Wood ◽  
Kerry M. Oliver ◽  
Ian Billick ◽  
Patrick Abbot

2004 ◽  
Vol 186 (19) ◽  
pp. 6626-6633 ◽  
Author(s):  
Laura Gómez-Valero ◽  
Mario Soriano-Navarro ◽  
Vicente Pérez-Brocal ◽  
Abdelaziz Heddi ◽  
Andrés Moya ◽  
...  

ABSTRACT Intracellular symbiosis is very common in the insect world. For the aphid Cinara cedri, we have identified by electron microscopy three symbiotic bacteria that can be characterized by their different sizes, morphologies, and electrodensities. PCR amplification and sequencing of the 16S ribosomal DNA (rDNA) genes showed that, in addition to harboring Buchnera aphidicola, the primary endosymbiont of aphids, C. cedri harbors a secondary symbiont (S symbiont) that was previously found to be associated with aphids (PASS, or R type) and an α-proteobacterium that belongs to the Wolbachia genus. Using in situ hybridization with specific bacterial probes designed for symbiont 16S rDNA sequences, we have shown that Wolbachia was represented by only a few minute bacteria surrounding the S symbionts. Moreover, the observed B. aphidicola and the S symbionts had similar sizes and were housed in separate specific bacterial cells, the bacteriocytes. Interestingly, in contrast to the case for all aphids examined thus far, the S symbionts were shown to occupy a similarly sized or even larger bacteriocyte space than B. aphidicola. These findings, along with the facts that C. cedri harbors the B. aphidicola strain with the smallest bacterial genome and that the S symbionts infect all Cinara spp. analyzed so far, suggest the possibility of bacterial replacement in these species.


2020 ◽  
Vol 168 (2) ◽  
pp. 174-183 ◽  
Author(s):  
Corentin Sochard ◽  
Stéphanie Morlière ◽  
Grégory Toussaint ◽  
Yannick Outreman ◽  
Akiko Sugio ◽  
...  

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