Such interdependent relationships are not unusual in the natural world. What is unusual, report Helen Dunbar, Nancy Moran, and colleagues in a new study published this week in the open access journal PLoS Biology, is that a single point mutation in Buchnera’s genome can have consequences for its aphid partner that are sometimes detrimental, and sometimes beneficial.
The authors probe Buchnera’s and A. pisum’s ability to tolerate heat. When exposed to high temperatures, Buchnera is supposed to activate special “heat-shock” genes whose products help to protect proteins from heat-related degradation. By using microarrays to assess activity of A. pisum and Buchnera genes, the researchers discovered that after a four-hour exposure to 35 °C temperature, some of their laboratory strains of Buchnera upregulated the heat-shock genes, but others did not. Further analysis showed the genetic basis for the difference: a single missing nucleotide in an adenine-filled stretch of DNA, called a promoter, that’s involved in activating the heat-shock gene. Testing at a range of temperatures from 15 °C to 35 °C showed that activation of the heat-shock gene was consistently lower in the lines with the missing nucleotide than in the normal bacteria.
What does this mean for A. pisum’s ability to tolerate tough conditions? To answer that, the researchers asked whether exposing juvenile aphid hosts of Buchnera with either long or short promoters to four hours of high temperatures (35 or 38 °C) affected their ability to reproduce. They found that few of the aphids with bacteria bearing short promoters reproduced after the heat treatment, while those with bacteria bearing the longer promoters had no trouble. In addition, aphids that had been exposed to the high temperatures and had the short-promoter-bearing bacteria weighed less as adults and had far fewer Buchnera inside them than did their counterparts with long-promoter-bearing bacteria.
Given these seemingly huge disadvantages to dropping a single adenine, it’s hard to believe the mutation could last long in a Buchnera population. Yet, by sequencing and comparing the Buchnera associated with various A. pisum lines, the researchers discovered that the short-promoter option had arisen and been fixed twice in laboratory stock and was also found at frequencies of 21% and 13%, respectively, in bacteria in field-collected aphids from Wisconsin and New York.
Population genetic theory predicts that when a mutation is maintained in a population at high frequencies, it likely confers some benefit to its bearer. What could be the advantage of carrying a gene that causes one to lose the ability to reproduce at high temperatures?
A clue to the answer comes from the wild populations in which the mutation was not found: those living in Arizona and Utah. Could the bacterial mutation confer a competitive advantage that’s only relevant in cooler climates? To find that out, the researchers performed a second test using a range of four-hour exposure temperatures. They discovered that short-promoter bacteria-bearing aphids produced progeny faster than did the normal ones when raised at 15 °C or 20 °C. Thus, though aphids containing bacterial symbionts with the heat-shock-promoter mutation fare worse than normal aphids after exposure to high temperatures, they do better under cool conditions, giving the mutation a selective advantage that causes it to be maintained in the population.
In addition to their explorations of A. pisum and its Buchnera, Moran’s team also looked for and found multiple-adenine stretches related to heat-shock genes in Buchnera symbiotic with other aphid species. This offers fertile ground for further study of the intriguing interplay among aphids, bacteria, and temperature.
Citation: Dunbar HE, Wilson ACC, Ferguson NR, Moran NA (2007) Aphid thermal tolerance is governed by a point mutation in bacterial symbionts. PLoS Biol 5(5): e96. doi:10.1371/journal.pbio.0050096.
Andrew Hyde | alfa
127 at one blow...
18.01.2017 | Stiftung Zoologisches Forschungsmuseum Alexander Koenig, Leibniz-Institut für Biodiversität der Tiere
How gut bacteria can make us ill
18.01.2017 | Helmholtz-Zentrum für Infektionsforschung
Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
18.01.2017 | Life Sciences
18.01.2017 | Information Technology
18.01.2017 | Life Sciences