Who is Drosophila from Plants

Location: science.ORF.at / Message: "A plant that cheats on fruit flies" "

Thanks to a new type of measurement method, functional imaging, the scientists from the Max Planck Institute for Chemical Ecology in Jena were able to trace the path of the fragrant molecules from the plant to the insect brain.

Deceptive plant

The genus Drosophila - fruit or vinegar flies use yeast as their main food. Their feelers and the olfactory bulbs made up of so-called glomeruli specialize in the typical odor molecules of growing yeasts. The smallest concentrations of molecules in the air are sufficient to point the fruit flies to the food source.

Many flowering plants, on the other hand, rely on insects as pollinators to ensure progeny and genetic variability. For example, they attract the animals with colored flower petals and scented bouquets. Once the pollinator has reached flowering, it is rewarded with nectar for transferring the pollen to another plant.

The arum plant Arum palaestinum however, it resorts to fraudulent means. The plant, also known as black calla, produces a smell in its flowers, which are purple-black on the inside, which people compare to that of fruity wine. With this scent, it was assumed, the black calla attracts its pollinators, namely fruit flies. These are not rewarded with nectar when they are in bloom, on the contrary, they are held captive in the bloom overnight and only released the next day.

Attracted by the smell of fermentation

To the study in "Current Biology":"A deceptive pollination system targeting drosophilids through olfactory mimicry of yeast" by Johannes Stökl et al.

MPG, J. Stökl

The arum tree traps fruit flies overnight.

As part of their study, the researchers around Marcus Stensmyr found that Arum palaestinum on average around 140 flies per plant belonging to eight different Drosophila species, including Drosophila melanogaster, the well-known model organism.

14 different chemical compounds to which the antennae of the flies reacted could be detected in the scent of the plant. To do this, the team electrically derived and recorded action potentials from the animals' antennae. The chemical analysis of the fragrances given off by the plant showed that they were mainly ester compounds. Particularly noticeable were two special fragrances that are characteristic of vinegar, especially aceto balsamico, and wine, i.e. two fermentation products produced by yeast.

"Abuse" of the fruit flies

In neurophysiological studies, fruit flies were then exposed to various natural scented bouquets, for example putrid peaches or bananas as well as Lambrusco (red wine) and Aceto Balsamico (vinegar). The electroantennograms were strikingly similar to the recordings with flies that were exposed to the smell of black calla - red wine and vinegar, i.e. the products obtained specifically through yeast fermentation, behaved almost identical to the calla smell.

"The flies cannot distinguish the arum from rotten fruits - they are cheated by the plant, because it only imitates the yeast smell, but does not even offer yeast as food," says study author Johannes Stökl. The insects are not even rewarded for their involuntary help as pollinators, but remain hungry and trapped in the flower until it opens again after 24 hours.

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