Abstract
Heteropterans produce 2-alkenals and 4-keto-2-alkenals that function as defense substances or pheromones. However, in spite of advances in heteropteran chemistry, it is still unclear how these compounds affect insect physiology. We found that exposure to 4-oxo-(E)-2-hexenal (OHE) induced permanent paralysis and death in crickets, an experimental model. The depletion of free thiols in leg tissues of OHE-treated crickets and the in vitro adduct formation of OHE with a thiol compound suggest that covalent binding of OHE to biologically active thiols is a potential cause affecting crickets’ locomotion.
Highlights
Heteropterans, or true bugs, are remarkable for their production of volatile chemicals such as (E)-2-hexenal, (E)-2-octenal, (E)-decenal, and 4-oxo-(E)-2-hexenal (OHE) in scent glands located in the dorsal abdomen in nymphs and in metathoracic scent glands in adults (Fig. 1)
OHE was synthesized by a one-step reaction described in Moreria and Millar [28]. 1-Butanethiol (1-BuSH), 5,50-dithiobis(nitrobenzoic acid) (DTNB), trichloroacetic acid (TCA), Triton X-100, (E)-2-pentenal, (E)-2-hexenal, (E)-2-octenal, (E)-2-hexen-1-ol, (E)-2-hexene, hexanal, and hexane were obtained from Sigma–Aldrich
Our results indicate that while exposure to a,b-unsaturated aldehydes with six to eight carbon chain lengths caused only moderate and temporary paralysis in crickets, exposure to OHE impaired the cricket’s locomotive ability resulting in permanent paralysis and death
Summary
Heteropterans, or true bugs, are remarkable for their production of volatile chemicals such as (E)-2-hexenal, (E)-2-octenal, (E)-decenal, and 4-oxo-(E)-2-hexenal (OHE) in scent glands located in the dorsal abdomen in nymphs and in metathoracic scent glands in adults (Fig. 1). Mixtures of these compounds are known to function as pheromones and as defense substances against predators in their natural habitats [1,2,3,4,5]. Of these compounds, (E)-2-hexenal has been reported to be a predator repellent [6], inhibitor of microbial growth [7], and in the plant literature it is reported for its role against herbivores [8,9,10].
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