Unexpected Effects of Low Doses of a Neonicotinoid Insecticide on Behavioral Responses to Sex Pheromone in a Pest Insect

In moths, which include many agricultural pest species, males are attracted by female-emitted sex pheromones. Although integrated pest management strategies are increasingly developed, most insect pest treatments rely on widespread use of neurotoxic chemicals, including neonicotinoid insecticides. Residual accumulation of low concentrations of these insecticides in the environment is known to be harmful to beneficial insects such as honey bees. This environmental stress probably acts as an “info-disruptor” by modifying the chemical communication system, and therefore decreases chances of reproduction in target insects that largely rely on olfactory communication. However, low doses of pollutants could on the contrary induce adaptive processes in the olfactory pathway, thus enhancing reproduction. Here we tested the effects of acute oral treatments with different low doses of the neonicotinoid clothianidin on the behavioral responses to sex pheromone in the moth Agrotis ipsilon using wind tunnel experiments. We show that low doses of clothianidin induce a biphasic effect on pheromone-guided behavior. Surprisingly, we found a hormetic-like effect, improving orientation behavior at the LD20 dose corresponding to 10 ng clothianidin. On the contrary, a negative effect, disturbing orientation behavior, was elicited by a treatment with a dose below the LD0 dose corresponding to 0.25 ng clothianidin. No clothianidin effect was observed on behavioral responses to plant odor. Our results indicate that risk assessment has to include unexpected effects of residues on the life history traits of pest insects, which could then lead to their adaptation to environmental stress.     

Localization of potential ion transport pathways in vesicular trichome cells of Atriplex halimus L.

The secreting glandular trichomes are recognized as an efficient structure that alleviates salt effects on Atriplex halimus. They are found on buds, young green stems, and leaves. They occupy both the leaf surfaces and give them a whitish color. Their histogenesis and ultrastructure were investigated in the third young leaves. They appear in early stage of plant development and its initiation continuous until just the leaf final development state. Each trichome contains two parts; a stalk which has high electron opacity, embedded in epidermal cells, and bears a second one which is unicellular, called bladder cell and has a low electron density. The bladder cell appears as a huge vacuole and the well-reduced cytoplasm which is pushed close to the wall, contains only a few organelles. Concurrently, the use of silver chloride precipitation technique shows that, in secretion process, salt follows a symplasmatic pathway which is consolidated by the presence of numerous plasmodesmata between the stalk cell(s), and the bladder one and the neighboring mesophyll cells. In addition, according to lanthanum-tracer study, salt can be excreted apoplastically. In fact, the heavy element can be transported via endocytosis vesicles, and by Golgi, endoplasmic reticulum, and lysosome (G.E.R.L.) network toward the storage vacuoles.     

Alleviation of drought stress in faba bean (Vicia faba L.) by exogenous application of β-aminobutyric acid (BABA)

Physiology and Molecular Biology of Plants - Drought stress is one of the most prevalent environmental factors limiting faba bean (Vicia faba L.) crop productivity. β-aminobutyric acid (BABA)...     

Distribution of phenolic compounds and antioxidant activity between young and old leaves of Carthamus tinctorius L. and their induction by salt stress

In the present work, we investigated the effect of salt stress on the distribution of safflower (Carthamus tinctorius L.) antioxidant system in relation to leaf age. The study was carried out under growth chamber conditions using seedlings of three cultivars which were subjected to 0 and 50 mM NaCl for 3 weeks. Leaf growth, water content, lipid peroxidation, and phenolic compound (total polyphenols, total flavonoids, and proanthocyanidins) concentration were measured at two leaf stages (young and old leaves). Leaf growth was affected by salinity only in Kairouan cultivar that also showed a significant decrease in old leaf water content. By contrast, Gabes and Tazarka cultivars maintained their old leaf water content constant and showed a reduction in that of young leaves. This could be attributed to a higher aptitude of the latter two cultivars to use absorbed sodium and chloride for osmotic adjustment in old leaves, keeping potassium for specific functions. Salt-induced lipid peroxidation was observed only in old leaves, whereas the accumulation of the major phenolic compounds under saline conditions was higher in young leaves, except in Gabes cultivar where no significant difference was found between the two leaf stages. A significant variability was also found between the three cultivars. The better behavior of salt-challenged leaves of Gabes and Tazarka cultivars compared to that of Kairouan cultivar may be related to their higher water content and the accumulation of polyphenols, in particular flavonoids that were shown to be efficiently involved in the restriction of salt-induced oxidative damages.     

Synthesis, characterization and preliminary screening of regioisomeric 1-(3-pyridazinyl)-3-arylpyrazole and 1-(3-pyridazinyl)-5-arylpyrazole derivatives towards cyclooxygenase inhibition

In a search for novel compounds with analgesic and anti-inflammatory activity, a series of regioisomeric 1-(3-pyridazinyl)-3-arylpyrazole (5a-f, 6a-f) and 1-(3-pyridazinyl)-5-arylpyrazole (7a-f, 8a-f) derivatives were synthesized. The structure of these regioisomers was confirmed by spectral techniques. The compounds were preliminarily screened at 8 microM concentration for their inhibitory activity against cyclooxygenase enzymes, COX-1 and COX-2, using a human whole blood test. The tested derivatives showed inhibitory activity for both enzymes and are worthy of further investigation for developing better leads.     

Interactive effects of salinity and iron deficiency in Medicago ciliaris

In calcareous salt-affected soils, iron availability to plants is subjected to the effects of both sodium and bicarbonate ions. Our aim was to study interactive effects of salinity and iron deficiency on iron acquisition and root acidification induced by iron deficiency in Medicago ciliaris L., a species commonly found in saline ecosystems. Four treatments were used: C, control treatment, complete medium (CM) containing 30 microM Fe; S, salt treatment, CM with 75 mM NaCl; D, deficient treatment, CM containing only 1 microM Fe; DS, interactive treatment, CM containing 1 microM Fe with 75 mM NaCl. Our study showed that plant growth and chlorophyll content were much more affected by the interactive treatment than by iron deficiency or by the salt treatment, indicating an additive effect of these constraints in DS plants. These results could be partially explained by Na accumulation in shoots as well as a limitation of nutrient uptake such as Fe and K under salt stress, under iron deficiency, and especially under their combined effect. The study also showed that root acidification was deeply diminished when iron deficiency was associated with salinity. This probably explained the decrease of Fe uptake and suggested that root proton pump activity would be inhibited by salinity.     

Enigmatic relationship of two Microsporum species

Unusual cultures of a Microsporum species were isolated from eleven patients who had either tinea capitis or tinea corporis or both. Although the macroconidia produced in the primary cultures resembled those of M. canis, hyphal morphology and colony characteristics were different from any of the more commonly occurring Microsporum species. Careful examination of subcultures showed that the isolates were composed of two species; M. canis and M. distortum, whose relationship remains enigmatic.     

Faunistic note on Culcoides (Diptera, Ceratopogonidae) from the governate of Monastir (Tunisia)

Following the arrival of blue-tongue in Tunisia, the authors report the results of the first survey made in Monastir. They show the existence of nine species of Culicoides, three of which are new to the country IC. paolae, C. imicola, C. newsteadi), that now brings to 22 the number of the known species.