Host nuclear genotype influences phenotype of a conditional mutualist symbiont

Abstract

Arthropods commonly carry maternally inherited intracellular bacterial symbionts that may profoundly influence host biology and evolution. The intracellular symbiont Rickettsia sp. nr. bellii swept rapidly into populations of the sweetpotato whitefly Bemisia tabaci in the south-western USA. Previous laboratory experiments showed female-bias and fitness benefits were associated with Rickettsia infection, potentially explaining the high frequencies of infection observed in field populations, but the effects varied with whitefly genetic line. Here, we explored whether host extranuclear or nuclear genes influenced the variation in the Rickettsia-host phenotype in two genetic lines of the whitefly host, each with Rickettsia-infected and uninfected sublines. Introgression between the Rickettsia-infected subline of one genetic line and the Rickettsia-uninfected subline of the other was used to create two new sublines, each with the maternally inherited extranuclear genetic lineages of one line (Rickettsia, two other symbionts and the mitochondria) and the nuclear genotype of the other. Performance assays comparing the original and new lines showed that in addition to Rickettsia, the interaction of Rickettsia infection with host nuclear genotype influenced development time and the sex ratio of the progeny, whereas the extranuclear genotype did not. Host nuclear genotype, but not extranuclear genotype, also influenced the titre of Rickettsia. Our results support the hypothesis that differences in host nuclear genotype alone may explain considerable within-population variation in host-symbiont phenotype and may contribute to the observed variation in Rickettsia-whitefly interactions worldwide.

Context‐dependent vertical transmission shapes strong endosymbiont community structure in the pea aphid, Acyrthosiphon pisum

“…Variable receptivity to HFSs, due to genetically encoded differences in internal physiology (e.g., Herren et al, 2014), would be akin to the process of habitat filtration. Our discovery that three abundant pea aphid clones In other insects, host genotype has been shown to influence HFS titres (Early & Clark, 2013;Hunter, Asiimwe, Himler, & Kelly, 2017), a finding of significance given the suggested effects of titre upon HFS transmission rates and on HFS-driven impacts on host-level phenotypes (Unckless et al, 2009). There is a clear need to study such effects in the pea aphid system, as the results obtained here were not quantitative (while further showing potential susceptibility to occasional false negatives; e.g., Table S11; Supplementary Results If within-host competition is indeed important in driving HFS structure, why are rare HFS combinations found at all in host populations?…”

“…In other insects, host genotype has been shown to influence HFS titres (Early & Clark, ; Hunter, Asiimwe, Himler, & Kelly, ), a finding of significance given the suggested effects of titre upon HFS transmission rates and on HFS‐driven impacts on host‐level phenotypes (Unckless et al., ). There is a clear need to study such effects in the pea aphid system, as the results obtained here were not quantitative (while further showing potential susceptibility to occasional false negatives; e.g., Table ; ).…”

Wolbachia dominate Spiroplasma in the co‐infected spider mite Tetranychus truncatus

“…However, these findings were confounded by the fact that the three symbiont‐infected strains were collected from different fields in Shenyang, whereas uninfected strain was obtained from a tetracycline‐treated W−S+ strain. The contrasting findings highlight the importance of controlling genetic background, which has been raised in other systems, such as in the whitefly Bemisia tabaci infected with Rickettsia (Hunter et al ., ) and in D. melanogaster infected by Wolbachia (Olsen et al ., ; Fry et al ., ).…”

Peer Review #3 of "Host and symbiont genetic contributions to fitness in a Trichogramma–Wolbachia symbiosis (v0.1)"

“…However the extent to which control is exerted by host and symbiont is often unknown. A recent study on the B. Manuscript to be reviewed and host-symbiont interactions (Hunter et al 2016). For infected T. kaykai females, offspring sex ratios are a function of the efficiency of Wolbachia-induced gamete duplication (the means by which PI Wolbachia converts male offspring to female offspring).…”