Sol g 2 is the major protein in
fire ant venom. It shares the highest sequence identity with Sol i 2 (
) and shares high structural homology with LmaPBP (pheromone-binding protein (PBP) from the ...cockroach
). We examined the specific Sol g 2 protein ligands from fire ant venom. The results revealed that the protein naturally formed complexes with hydrocarbons, including decane, undecane, dodecane, and tridecane, in aqueous venom solutions. Decane showed the highest affinity binding (K
) with the recombinant Sol g 2.1 protein (rSol g 2.1). Surprisingly, the mixture of alkanes exhibited a higher binding affinity with the rSol g 2.1 protein compared to a single one, which is related to molecular docking simulations, revealing allosteric binding sites in the Sol g 2.1 protein model. In the trail-following bioassay, we observed that a mixture of the protein sol g 2.1 and hydrocarbons elicited
worker ants to follow trails for a longer time and distance compared to a mixture containing only hydrocarbons. This suggests that Sol g 2.1 protein may delay the evaporation of the hydrocarbons. Interestingly, the piperidine alkaloids extracted have the highest attraction to the ants. Therefore, the mixture of hydrocarbons and piperidines had a synergistic effect on the trail-following of ants when both were added to the protein.
Fluorescent analogues of the gypsy moth sex pheromone (+)-disparlure (
1
) and its enantiomer (−)-disparlure (
ent
-
1
) were designed, synthesized, and characterized. The fluorescently labelled ...analogues 6-FAM (+)-disparlure and
1a
6-FAM (−)-disparlure
ent
-
1a
were prepared by copper-catalyzed azide-alkyne cycloaddition of disparlure alkyne and 6-FAM azide. These fluorescent disparlure analogues
1a
and
ent
-
1a
were used to measure disparlure binding to two pheromone-binding proteins from the gypsy moth,
Ldis
PBP1 and
Ldis
PBP2. The fluorescence binding assay showed that
Ldis
PBP1 has a stronger affinity for 6-FAM (−)-disparlure
ent
-
1a
, whereas
Ldis
PBP2 has a stronger affinity for 6-FAM (+)-disparlure
1a
, consistent with findings from previous studies with disparlure enantiomers. The 6-FAM disparlure enantiomers appeared to be much stronger ligands for
Ldis
PBPs, with binding constants (
K
d
) in the nanomolar range, compared to the fluorescent reporter 1-NPN (which had
K
d
values in the micromolar range). Fluorescence competitive binding assays were used to determine the displacement constant (
K
i
) for the disparlure enantiomers in competition with fluorescent disparlure analogues binding to
Ldis
PBP1 and
Ldis
PBP2. The
K
i
data show that disparlure enantiomers can effectively displace the fluorescent disparlure from the binding pocket of
Ldis
PBPs and, therefore, occupy the same binding site.
The honey bee is responsible for pollination of a large proportion of crop plants, but the health of honey bee populations has been challenged by the parasitic mite Varroa destructor. Mite ...infestation is the main cause of colony losses during the winter months, which causes significant economic challenges in apiculture. Treatments have been developed to control the spread of varroa. However, many of these treatments are no longer effective due to acaricide resistance. In a search of varroa-active compounds, we tested the effect of dialkoxybenzenes on the mite. A structure-activity relationship revealed that 1-allyloxy-4-propoxybenzene is most active of a series of dialkoxybenzenes tested. We found that three compounds (1-allyloxy-4-propoxybenzene, 1,4-diallyloxybenzene and 1,4-dipropoxybenzene) cause paralysis and death of adult varroa mites, whereas the previously discovered compound, 1,3-diethoxybenzene, which alters host choice of adult mites in certain conditions, did not cause paralysis. Since paralysis can be caused by inhibition of acetylcholinesterase (AChE), a ubiquitous enzyme in the nervous system of animals, we tested dialkoxybenzenes on human, honey bee and varroa AChE. These tests revealed that 1-allyloxy-4-propoxybenzene had no effects on AChE, which leads us to conclude that 1-allyloxy-4-propoxybenzene does not exert its paralytic effect on mites through AChE. In addition to paralysis, the most active compounds affected the ability of the mites to find and remain at the abdomen of host bees provided during assays. A test of 1-allyloxy-4-propoxybenzene in the field, during the autumn of 2019 in two locations, showed that this compound has promise in the treatment of varroa infestations.
Honey bees and their ectoparasite
Varroa destructor
communicate through chemical signals among themselves, but they also eavesdrop on each other’s chemical cues. We summarize semiochemicals of honey ...bees and
Varroa
, and their roles in honey bee-
Varroa
interactions. We also give an overview of current
Varroa
control methods, which can be classified into three categories: (1) chemical control methods with acaricides, (2) biotechnical intervention, and (3) bee breeding programs. Widely used synthetic chemical acaricides are failing due to the emergence of resistant mites. Therefore, new methods are being sought for
Varroa
control, and methods that target the semiochemical interactions between bees and mites are among the candidates. We review our discovery of compounds that alter the host choice of
Varroa
mites (from nurse to forager) in laboratory tests. Any semiochemical-based methods are still in the experimental stage and need validation in the field.
The ectoparasitic mite,
Varroa destructor
Anderson and Trueman (Acar: Varroidae), is a major threat for the honey bee,
Apis mellifera
L. Varroa behavior and physiology are influenced by compounds ...produced by the honey bee, as well as cues from the general colony environment. As part of our effort to disrupt varroa host chemosensing, we tested 1-allyloxy-4-propoxybenzene,
3c
{
3,6
}, a known feeding deterrent of Lepidoptera larvae and a repellent of mosquitoes of similar activity to DEET. Its effect on varroa mites was evaluated by electrophysiological and behavioral bioassays. Its effect on honey bee chemosensing was also assessed. Compound
3c{
3,6
}
is sensed by honey bees, but the detection of the compound alone by varroa is not clear. The electrophysiological study showed that
3c{
3,6
}
decreases the varroa foreleg responses towards head space odor of nurse bees. However, the response of honey bee antennae towards nurse bee head space odor was not affected. Consistent with electrophysiological studies, in the presence of
3c{
3,6
}
, the ability of varroa to reach any host decreased at the end of the experiment. No lethal effect to the honey bees was recorded. These data showed that
3c{
3,6
}
affects the peripheral olfactory system of varroa by disrupting the chemical recognition process.
The ectoparasitic mite, Varroa destructor, is considered to be one of the most significant threats to apiculture around the world. Chemical cues are known to play a significant role in the ...host-finding behavior of Varroa. The mites distinguish between bees from different task groups, and prefer nurses over foragers. We examined the possibility of disrupting the Varroa--honey bee interaction by targeting the mite's olfactory system. In particular, we examined the effect of volatile compounds, ethers of cis 5-(2'-hydroxyethyl) cyclopent-2-en-1-ol or of dihydroquinone, resorcinol or catechol. We tested the effect of these compounds on the Varroa chemosensory organ by electrophysiology and on behavior in a choice bioassay. The electrophysiological studies were conducted on the isolated foreleg. In the behavioral bioassay, the mite's preference between a nurse and a forager bee was evaluated.
We found that in the presence of some compounds, the response of the Varroa chemosensory organ to honey bee headspace volatiles significantly decreased. This effect was dose dependent and, for some of the compounds, long lasting (>1 min). Furthermore, disruption of the Varroa volatile detection was accompanied by a reversal of the mite's preference from a nurse to a forager bee. Long-term inhibition of the electrophysiological responses of mites to the tested compounds was a good predictor for an alteration in the mite's host preference.
These data indicate the potential of the selected compounds to disrupt the Varroa--honey bee associations, thus opening new avenues for Varroa control.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Previous research showed that the presence of older workers causes a delayed onset of foraging in younger individuals in honey bee colonies, but a specific worker inhibitory factor had not yet been ...identified. Here, we report on the identification of a substance produced by adult forager honey bees, ethyl oleate, that acts as a chemical inhibitory factor to delay age at onset of foraging. Ethyl oleate is synthesized de novo and is present in highest concentrations in the bee's crop. These results suggest that worker behavioral maturation is modulated via trophallaxis, a form of food exchange that also serves as a prominent communication channel in insect societies. Our findings provide critical validation for a model of self-organization explaining how bees are able to respond to fragmentary information with actions that are appropriate to the state of the whole colony.
P450(cam) (CYP101A1) is a bacterial monooxygenase that is known to catalyze the oxidation of camphor, the first committed step in camphor degradation, with simultaneous reduction of oxygen (O2). We ...report that P450(cam) catalysis is controlled by oxygen levels: at high O2 concentration, P450(cam) catalyzes the known oxidation reaction, whereas at low O2 concentration the enzyme catalyzes the reduction of camphor to borneol. We confirmed, using (17)O and (2)H NMR, that the hydrogen atom added to camphor comes from water, which is oxidized to hydrogen peroxide (H2O2). This is the first time a cytochrome P450 has been observed to catalyze oxidation of water to H2O2, a difficult reaction to catalyze due to its high barrier. The reduction of camphor and simultaneous oxidation of water are likely catalyzed by the iron-oxo intermediate of P450(cam) , and we present a plausible mechanism that accounts for the 1:1 borneol:H2O2 stoichiometry we observed. This reaction has an adaptive value to bacteria that express this camphor catabolism pathway, which requires O2, for two reasons: 1) the borneol and H2O2 mixture generated is toxic to other bacteria and 2) borneol down-regulates the expression of P450(cam) and its electron transfer partners. Since the reaction described here only occurs under low O2 conditions, the down-regulation only occurs when O2 is scarce.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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