First published: 15 September 2025.
A recently published article from Physiological Entomology, “Coinfection of Mesenetia and rescuing Wolbachia in the coconut hispine beetle”, is the first report of coinfection of mod−/resc+ Wolbachia and other cytoplasmic incompatibility (CI) inducers, which explains why Wolbachia in coinfected hosts does not induce CI.
Maternally transmitted bacterial symbionts can manipulate a host insect’s reproduction. One such manipulation is cytoplasmic incompatibility (CI). In CI, symbionts cause toxic effects in sperm and kill embryos unless they are rescued by an antidote of maternal origin provided by the symbionts. Thus, uninfected females seldom produce offspring by mating with infected males. Thus far, seven bacterial endosymbionts are known as CI inducers.
Different species or strains of CI-inducing bacterial symbionts may coinfect in a single host. It has been known that some CI-inducing symbionts induce CI in singly infected hosts, but not when coinfection occurs. However, the mechanisms of this phenomenon are still unknown.
“Wolbachia and its ability to sterilise host-insect males have attracted great interest from people concerning insect pests because of its potential for pest control.
Understanding how Wolbachia loses its ability to sterilise host males is of great importance for sustainable control.”
– Dr. Shun-ichiro Takano
In this study, we found that coconut hispine beetles in Japan were infected with Mesenetia, Wolbachia or both. Crossing tests revealed that Mesenetia induced CI in both singly and co-infected males. Coinfected Wolbachia did not induce CI; however, a part of singly infected Wolbachia did.
Genetic analysis showed that singly and co-infected Wolbachia belonged to different strains, the former strain causes both toxic and rescuing effects (referred to as mod+/resc+) and the latter one causes no toxic effect but can rescue it (referred to as mod−/resc+). Mod+/resc+ is considered to have evolved into mod−/resc+.
This is the first report of coinfection of mod−/resc+ Wolbachia and other CI inducers, which explains why Wolbachia in coinfected hosts does not induce CI. Also, this is the first report of a reproductive benefits of hosts infected with mod−/resc+ Wolbachia when coinfection with Mesenetia occurs. This is because coinfected females can rescue both CI induced by Mesenetia and Wolbachia.
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