Alternative on ants
Plants do all they can do to prevent getting eaten. In this regard do the tropical tococa bush and ants work together. Tococa gives the ants a home and as thanks the ants keep the plant free of herbivorous insects and pathogens. But even without an ant colony are the tococa plants able to defend themselves discovered German researchers.
The nibbling of caterpillars at tococa leaves resulted in the production of toxic and semi-volatile aldoximes. The researchers discovered that in addition to the toxic version, the plant also produced a large amount of a safe aldoximes version. This safe aldoximes version stays present in high amounts for up to three days after insect feeding. Moreover, the researchers noticed that both aldoximes where only present in the direct surroundings of the insect feeding site.
The researchers studied the safe aldoximes version in more detail. Hereby they noticed that the safe aldoxines were transformed into the toxic version by enzymes from insect intestines. While this did not occur with enzymes from leaves. The researchers also noticed that the toxic aldoximes version, although in large concentrations, can kill bacteria.
Unknown regulation
The last question the researchers tried to answer was those of how the production of both aldoximes is regulated. For this the researchers studied how the production of the well-known insect response factor JA-Ile corresponds with that of that of the aldoximes. They noticed that from the different JA-Ile inducing actions, only insect herbivory resulted in the production of the toxic aldoximes. The safe aldoximes version was induced by all the different JA-Ile inducers tested, but the induction pattern did not correspond to that of JA-Ile. Suggesting that the production of aldoximes by the plant is regulated in a different, up to now unknown, way than that of JA-Ile.
So, it turns out that tococa bushes can even without their defending ants defend themselves against herbivorous insects. Even though, the plant probably prefers its ant defenders, considering the low energy cost of housing them.
Literature
Andrea T Müller, Yoko Nakamura, Michael Reichelt, Katrin Luck, Eric Cosio, Nathalie D Lackus, Jonathan Gershenzon, Axel Mithöfer, and Tobias G Köllner. (2023) Biosynthesis, herbivore induction, and defensive role of phenylacetaldoxime glucoside, Plant Physiology; kiad448, https://doi.org/10.1093/plphys/kiad448
Plant en Zo 