Rapid evolution ofWolbachiaincompatibility types

Abstract

In most insects, the endosymbiont Wolbachia induces cytoplasmic incompatibility (CI), an embryonic mortality observed when infected males mate either with uninfected females or with females infected by an incompatible Wolbachia strain. Although the molecular mechanism of CI remains elusive, it is classically viewed as a modification -rescue model, in which a Wolbachia mod function disables the reproductive success of the sperm of infected males, unless eggs are infected and express a compatible resc function. The extent to which the modification -rescue model can predict highly complex CI pattern remains a challenging issue. Here, we show the rapid evolution of the mod -resc system in the Culex pipiens mosquito. We have surveyed four incompatible laboratory isofemale lines over 50 generations and observed in two of them that CI has evolved from complete to partial incompatibility (i.e. the production of a mixture of compatible and incompatible clutches). Emergence of the new CI types depends only on Wolbachia determinants and can be simply explained by the gain of new resc functions. Evolution of CI types in Cx. pipiens thus appears as a gradual process, in which one or several resc functions can coexist in the same individual host in addition to the ones involved in the self-compatibility. Our data identified CI as a very dynamic process. We suggest that ancestral and mutant Wolbachia expressing distinct resc functions can co-infect individual hosts, opening the possibility for the mod functions to evolve subsequently. This gives a first clue towards the understanding of how Wolbachia reached highly complex CI pattern in host populations.

Sharing cells with Wolbachia: the transovarian vertical transmission of Culex pipiens densovirus

“…w Pip groups of these lines have been assigned based on a PCR/RFLP test on pool of larvae using pk1 primers as previously described (Dumas et al, ; Altinli et al ., ) and were regularly verified during the experiments. We introduced the cytoplasm of Tunis and Harash lines, along with their respective w Pip strains, into the Slab nuclear background as described by Duron and colleagues (). With this backcrossing protocol we have established BcTunis and BcHarash lines with the same genetic background (over 97% of genome replacement of the original lines by Slab nuclear genome is estimated) and different Wolbachia types ( w PipI and w PipIV respectively, Supporting Information Table 1).…”

Wolbachia: Can we save lives with a great pandemic?

“…For instance, the lock and key model suggests that each strain has its own encrypted locks and keys. The known strain incompatibilities, however, quickly demand a questionably large number of different locks and keys, especially considering the speed with which new incompatibilities arise [22]. The mistiming model also fails to account for strain specificity.…”

Molecular data reveal a cryptic species within the Culex pipiens mosquito complex

“…Mosquitoes of the Culex pipiens complex are naturally infected by a variety of CI‐inducing Wolbachia strains belonging to the w Pip clade (Rasgon & Scott, ; Duron et al ., ; Atyame et al ., ). This system is characterized by a rapid diversification of CI determinants (Duron et al ., ; Nor et al ., ) that has led to an unrivalled variety of crossing types, including uni‐ and bi‐directionally incompatible w Pip strain types (Guillemaud et al ., ; Duron et al ., ; Atyame et al ., ; Atyame et al ., ). The two most widespread members of this species complex are the common house mosquito, C. pipiens , and the southern house mosquito, Culex quinquefasciatus (Vinogradova, ; Smith & Fonseca, ; Farajollahi et al ., ).…”