Exposure to (Z)-11-hexadecenal [(Z)-11-16:Ald] increases Brassica nigra

It is well established that plants emit, detect and respond to volatile organic compounds; however, knowledge on the ability of plants to detect and respond to volatiles emitted by non-plant organisms is limited. Recent studies indicated that plants detect insect-emitted volatiles that induce defence responses; however, the mechanisms underlying this detection and defence priming is unknown. Therefore, we explored if exposure to a main component of Plutella xylostella female sex pheromone namely (Z)-11-hexadecenal [(Z)-11-16:Ald] induced detectable early and late stage defence-related plant responses in Brassica nigra.Exposure to biologically relevant levels of vapourised (Z)-11-16:Ald released from a loaded septum induced a change in volatile emissions of receiver plants after herbivore attack and increased the leaf area consumed by P. xylostella larvae. Further experiments examining the effects of the (Z)-11-16:Ald on several stages of plant defence-related responses showed that exposure to 100 ppm of (Z)-11-16:Ald in liquid state induced depolarisation of the transmembrane potential (Vm), an increase in cytosolic calcium concentration [Ca2+]cyt, production of H2O2and an increase in expression of reactive oxygen species (ROS)-mediated genes and ROS-scavenging enzyme activity.

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Fig: Partial Least Squares – Discriminant Analysis (PLS-DA) based on plant volatile emissions after plant exposure to vapourised (Z)-11-16:Ald and non-exposed controls with cross validation based on 50 submodels (fivefold outer loop and fourfold inner loop). Pairwise tests were performed, based on PLS-DA with 999 permutations, to highlight the difference between treatments with n = 9 to 12. ns indicates non-significant differences.

The results suggest that exposure to volatile (Z)-11-16:Ald increases the susceptibility of B. nigrato subsequent herbivory. This unexpected finding, suggest alternative ecological effects of detecting insect pheromone to those reported earlier. Experiments conducted in vitro showed that high doses of (Z)-11-16:Ald induced defence-related responses, but further experiments should assess how specific the response is to this particular aldehyde.

Brosset, A., Islam, M., Bonzano, S. et al. Exposure to (Z)-11-hexadecenal [(Z)-11-16:Ald] increases Brassica nigra susceptibility to subsequent herbivory. Sci Rep 11, 13532 (2021). https://doi.org/10.1038/s41598-021-93052-8

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