Parasitic inhibition of cell death facilitates symbiosis

Abstract

Symbiotic microorganisms have had a large impact on eukaryotic evolution, with effects ranging from parasitic to mutualistic. Mitochondria and chloroplasts are prime examples of symbiotic microorganisms that have become obligate for their hosts, allowing for a dramatic extension of suitable habitats for life. Out of the extraordinary diversity of bacterial endosymbionts in insects, most are facultative for their hosts, such as the ubiquitous Wolbachia, which manipulates host reproduction. Some endosymbionts, however, have become obligatory for host reproduction and/or survival. In the parasitoid wasp Asobara tabida the presence of Wolbachia is necessary for host oogenesis, but the mechanism involved is yet unknown. We show that Wolbachia influences programmed cell death processes (a host regulatory feature typically targeted by pathogens) in A. tabida, making its presence essential for the wasps' oocytes to mature. This suggests that parasite strategies, such as bacterial regulation of host apoptosis, can drive the evolution of host dependence, allowing for a swift transition from parasitism to mutualism.apoptosis ͉ Asobara tabida ͉ Wolbachia

The effects of, and interactions between, Cardinium and Wolbachia in the doubly infected spider mite Bryobia sarothamni

“…Bordenstein and Werren, 2000;Montenegro et al, 2006), or led to an increase in fecundity (Vavre et al, 1999;Dobson et al, 2004). In a few other arthorpods and in all nematodes, Wolbachia is obligatory, and thus required for host fertility (Bandi et al, 2001;Pannebakker et al, 2007). Cardinium is known to increase fecundity in Metaseiulus occidentalis (Weeks and Stouthamer, 2004).…”

Symbiosis as a General Principle in Eukaryotic Evolution

“…As a likely consequence, elimination of Wolbachia by antibiotic treatment results in massive apoptosis ( programmed cell death) of the ovaries, leaving the wasp reproductively sterile. It has been argued that, over evolutionary time, the wasp apoptotic pathways have gained heightened responsiveness, in compensation for the inhibitory manipulation by Wolbachia (Pannebakker et al 2007). Importantly, this effect is constitutive ( presumably because Wolbachia is always present under natural conditions), with the consequence that appropriate apoptotic signaling requires the manipulative intervention of the Wolbachia bacteria.…”

Symbiosis as a source of selectable epigenetic variation: taking the heat for the big guy

“…If A. tabida females carrying Wolbachia are treated with antibiotics that kill the symbiotic bacteria, the female wasps are unable to produce mature oocytes, and thus cannot reproduce. In fact, without the bacteria, the ovaries undergo apoptosis (Dedeine et al 2001;Pannebakker et al 2007). Unlike the squids, which receive their symbionts 'horizontally' from the sea water, A. tabida infects its juveniles 'vertically' through the egg cytoplasm.…”