PMID:17425405

Citation	Dunbar, HE, Wilson, AC, Ferguson, NR and Moran, NA (2007) Aphid thermal tolerance is governed by a point mutation in bacterial symbionts. PLoS Biol. 5:e96
Abstract	Symbiosis is a ubiquitous phenomenon generating biological complexity, affecting adaptation, and expanding ecological capabilities. However, symbionts, which can be subject to genetic limitations such as clonality and genomic degradation, also impose constraints on hosts. A model of obligate symbiosis is that between aphids and the bacterium Buchnera aphidicola, which supplies essential nutrients. We report a mutation in Buchnera of the aphid Acyrthosiphon pisum that recurs in laboratory lines and occurs in field populations. This single nucleotide deletion affects a homopolymeric run within the heat-shock transcriptional promoter for ibpA, encoding a small heat-shock protein. This Buchnera mutation virtually eliminates the transcriptional response of ibpA to heat stress and lowers its expression even at cool or moderate temperatures. Furthermore, this symbiont mutation dramatically affects host fitness in a manner dependent on thermal environment. Following a short heat exposure as juveniles, aphids bearing short-allele symbionts produced few or no progeny and contained almost no Buchnera, in contrast to aphids bearing symbionts without the deletion. Conversely, under constant cool conditions, aphids containing symbionts with the short allele reproduced earlier and maintained higher reproductive rates. The short allele has appreciable frequencies in field populations (up to 20%), further supporting the view that lowering of ibpA expression improves host fitness under some conditions. This recurring Buchnera mutation governs thermal tolerance of aphid hosts. Other cases in which symbiont microevolution has a major effect on host ecological tolerance are likely to be widespread because of the high mutation rates of symbiotic bacteria and their crucial roles in host metabolism and development.
Links	PubMed PMC1847839 Online version:10.1371/journal.pbio.0050096
Keywords	Animals; Aphids/microbiology; Aphids/physiology; Bacterial Proteins/genetics; Base Sequence; Buchnera/genetics; Heat-Shock Proteins/genetics; Hot Temperature; Molecular Sequence Data; Point Mutation; Promoter Regions, Genetic/physiology; Symbiosis
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
9ENTR:G0T621		GO:0033638: modulation by symbiont of host response to heat	ECO:0000314:		P		Figure 1c shows that the 5A-long form of the gene is upregulated in response to heat stress more than the 5A-short form, and figure 4 shows that aphids with Buchnera with the 5A-long form of ibpA have higher fecundity at higher temperatures than aphids with Buchnera with the 5A-short form.	complete CACAO 5219
9ENTR:G0T621	involved_in	GO:0033638: modulation by symbiont of host response to heat	ECO:0000314: direct assay evidence used in manual assertion		P		Seeded From UniProt	complete

References

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