Researchers from the Max Planck Institute for Chemical Ecology found that the specialist moth Heliothis subflexa benefits from secondary plant components by turning the original defensive function of these compounds into its own advantage. Withanolides, which are present in Physalis plants, usually act as immune suppressants and feeding deterrents in insects. Surprisingly, Heliothis subflexa uses these plant defenses as immune-system boosters. Moreover, withanolides protect the moth from harmful effects caused by pathogenic bacteria. The new study demonstrates a unique benefit to host-plant specialization. (Nature Communications, August 2016, doi: 10.1038/NCOMMS12530).
Insects versus plants in the evolutionary arms race: specialists and generalists
In order to survive and to repel herbivores, many plants defend themselves by producing toxic or deterrent substances. In the course of evolution, many insects have succeeded in adapting to the defensive chemistry of their host plants and thereby circumventing plants’ defense mechanisms.
However, the plants have also adapted their defensive system to further protect themselves against their enemies, which, in turn, generated counter-adaptations in the insects; biologists refer to this phenomenon as an “evolutionary arms race” between plants and insects. Many insects are plant pests which can be categorized as “specialists” and “generalists.”
Whereas generalists feed on many different plants, specialists have adapted to one or few closely related plant species as their food. The moth species Heliothis subflexa analyzed in this new study is such a host specialist.
Withanolides provide H. subflexa with direct and indirect protection
The researchers measured and compared the effects of withanolides on relative weight gains, survival rates and the immune status in two moth species: the specialist Heliothis subflexa and the generalist Heliothis virescens. They knew from earlier studies that the specialist moth possesses a weaker immune response compared to the closely related generalist.
“We were surprised to find that only Heliothis subflexa benefits from withanolides by increasing larval growth and immune system activity, but not its close relative, Heliothis virescens,” says Hanna M. Heidel-Fischer, the leader of the study.
Furthermore, the research team from the Department of Entomology found that withanolides protect the specialist, but not the generalist, from the growth-suppressive effects of an infection caused by the bacterial pathogen Bacillus thuringiensis. “Larvae of Heliothis subflexa could theoretically profit in two ways from Physalis fruits: First, withanolides display antibacterial and immune stimulant activity. Furthermore, the Physalis fruit is covered by a calyx that creates a so-called enemy-free space,” concludes co-author Heiko Vogel.
Physalis: A plant with promising properties
Plants of the genus Physalis, also known as ground cherries, have a long history as a medicinal herb in India and the Middle East. The medicinal importance of Physalis plants is mainly due to the presence of steroidal lactones, the withanolides. Withanolides exhibit potential anti-cancer, anti-inflammatory and apoptotic activities. However, the actual role of withanolides in Physalis plants is defense against herbivores. Withanolides have been shown to be potent anti-feeding deterrents as well as immunosuppressants in insects.
These effects can be attributed to possible interactions of withanolides with signal transduction pathways in the cells. For instance, previous studies have shown that withanolides may cause molting disorders in insects, suggesting that the anti-feeding and immunosuppressive effects arise from the disruptive effect of withanolides on the development of non-adapted insects. These toxic effects of withanolides on herbivorous insects suggest an adaptive benefit, since few insect species are known to feed on Physalis plants with impunity.
Heliothis subflexa: A Physalis specialist
Larvae of the Heliothis subflexa moth are probably best known for their ability to feed on Physalis plants, a plant genus that includes species also attractive to humans, such as the cape gooseberry and tomatillo. In contrast to their close relative Heliothis virescens, a generalist that feeds on at least 14 different plant families but not on Physalis, Heliothis subflexa larvae feed exclusively on Physalis fruits, and it is the only Heliothis species to do so. Physalis fruits are enclosed by a thin-walled, inflated calyx called a “lantern”.
The lantern provides a so-called enemy-free space for fruit-feeding larvae of Heliothis subflexa, which could be demonstrated in earlier studies. However, the impact of withanolides on specialized Heliothis subflexa had not been evaluated prior to this study. With the known immunosuppressive properties of withanolides in mind, the researchers aimed to examine the specialization of Heliothis subflexa on Physalis in the context of ecological immunology.
“Ecological immunology combines classical studies of the immune system with an ecological perspective to evaluate the costs and benefits of defense against pathogens in the natural environment, and the manner in which natural selection shapes the immune system,” explains Andrea Barthel, the first author of the publication. Further studies will now focus on the mechanism by which the specialist moth circumvents plant defenses. Moreover, experiments are planned to elucidate the effect withanolides have on the bacterial communities on the plant surface as well as in the gut of the specialist insect. [AB/HHF/AO]
Barthel, A., Vogel, H., Pauchet, Y., Pauls, G., Kunert, G., Groot, A. T., Boland, W., Heckel, D. G., Heidel-Fischer, H. (2016). Immune modulation enables a specialist insect to benefit from antibacterial withanolides in its host plant. Nature Communications. DOI: 10.1038/NCOMMS12530
Hanna Heidel-Fischer, Max Planck Institute for Chemical Ecology, Hans-Knöll-Str. 8, 07743 Jena, Germany, +49 3641 57-1516, email@example.com
Contact and Media Requests:
Angela Overmeyer M.A., Max Planck Institute for Chemical Ecology, Hans-Knöll-Str. 8, 07743 Jena, +49 3641 57-2110, E-Mail firstname.lastname@example.org
Download high-resolution images via http://www.ice.mpg.de/ext/downloads2016.html
http://www.ice.mpg.de/ext/index.php?id=entomology Department of Entomology
Angela Overmeyer | Max-Planck-Institut für chemische Ökologie
Mass spectrometry sheds new light on thallium poisoning cold case
14.12.2018 | University of Maryland
Protein involved in nematode stress response identified
14.12.2018 | University of Illinois College of Agricultural, Consumer and Environmental Sciences
The more objects we make "smart," from watches to entire buildings, the greater the need for these devices to store and retrieve massive amounts of data quickly without consuming too much power.
Millions of new memory cells could be part of a computer chip and provide that speed and energy savings, thanks to the discovery of a previously unobserved...
What if, instead of turning up the thermostat, you could warm up with high-tech, flexible patches sewn into your clothes - while significantly reducing your...
A widely used diabetes medication combined with an antihypertensive drug specifically inhibits tumor growth – this was discovered by researchers from the University of Basel’s Biozentrum two years ago. In a follow-up study, recently published in “Cell Reports”, the scientists report that this drug cocktail induces cancer cell death by switching off their energy supply.
The widely used anti-diabetes drug metformin not only reduces blood sugar but also has an anti-cancer effect. However, the metformin dose commonly used in the...
A research team from the University of Zurich has developed a new drone that can retract its propeller arms in flight and make itself small to fit through narrow gaps and holes. This is particularly useful when searching for victims of natural disasters.
Inspecting a damaged building after an earthquake or during a fire is exactly the kind of job that human rescuers would like drones to do for them. A flying...
Over the last decade, there has been much excitement about the discovery, recognised by the Nobel Prize in Physics only two years ago, that there are two types...
12.12.2018 | Event News
10.12.2018 | Event News
06.12.2018 | Event News
14.12.2018 | Power and Electrical Engineering
14.12.2018 | Physics and Astronomy
14.12.2018 | Physics and Astronomy