ABSTRACT
Aphids are major agricultural pests that cause significant yield losses of crops each year. (E)-β-farnesene (EβF), as the main component of the aphid alarm pheromones, can interrupt aphid feeding and cause other conspecies in the vicinity to become agitated or disperse from their host plant. Furthermore, EβF can function as a kairomone in attracting aphid predators. EβF synthase genes, which encode enzymes that convert farnesyl diphosphate (FPP) to the acyclic sesquiterpene EβF, have been isolated and characterized from peppermint (Mentha × piperita and Mentha asiatica), Yuzu (Citrus junos), Douglas fir (Pseudotsuga menziesii), sweet wormwood (Artemisia annua) and chamomile (Matricaria recutita), respectively. Transgenic plant overexpressing EβF synthase genes has been one of the most efficient strategies for aphid management. In this review, the current statuses of transgenic plants engineered for aphid resistance were summarized. The plant-derived EβF synthase genes with their potential roles in aphid management via genetic-modified (GM) approaches were reviewed. The existing problem in GM plants with EβF synthase gene, such as low EβF emission was usually detected in the transgenic plant, was discussed and the development direction in this area was proposed.
ABSTRACT
The capability to perceive and emit alarm substances, such as 2-heptanone, makes animals aware of the presence of danger, leading to some strategies directed towards survival. Strategies of survival involve emotional memory which is processed by deep temporal lobe structures, such as amygdaloid complex and hippocampus. In the Wistar rat, 2-heptanone produces anxiety-like behavior and an increased firing rate of basal amygdaline neurons. However, it is unknown whether 2-heptanone modifies the responsivity of medial amygdaline-hippocampal connection. Therefore, we placed a group (n=10) of Wistar rats in a plexiglass cage impregnated with 2-heptanone. Rats from control group (n=10) were introduced into a similar clean cage. Twenty four hours later we obtained single-unit extracellular recordings from the hippocampus (CA1-CA3) neurons identified by their connection to medial amygdala. Although the basal neuronal firing rate was similar between groups, first order interval distribution histogram analysis showed that 2-heptanone produced shorter intervals of firing rate. Peristimulus histograms indicated that: i) the amygdaline stimulation produces an increased firing rate in hippocampal neurons; and ii) this response is increased and enlarged on the 2-heptanone group. Since a single exposure to an alarm pheromone seems to facilitate the amygdala-hippocampal connection, results suggest the initial formation of contextual memories related with fear.
La percepción olfatoria de feromonas de alarma, como la 2-heptanona, promueve ciertas estrategias de supervivencia con la participación de la memoria emocional, integrada en estructuras del lóbulo temporal, como la amígdala y el hipocampo. En la rata Wistar, la olfacción de 2-heptanona genera conductas sugerentes de ansiedad y un incremento de la tasa de disparo neuronal del núcleo basal de la amígdala. Sin embargo, no se conoce si la 2-heptanona modifica la responsividad de la conexión amígdala medial-hipocampo. Un grupo de ratas Wistar (n=10) fue colocado dentro de una caja de acrílico impregnada con 2-heptanona; el grupo control (n=10) fue introducido en una caja limpia. Veinticuatro horas después se obtuvo el registro unitario extracelular de neuronas del hipocampo (CA1-CA3) identificadas por su conexión con la amígdala medial. Aunque la tasa de disparo basal fue similar entre los grupos experimentales, el histograma de distribución de intervalos de primer orden indicó un predominio de intervalos de breve duración en el grupo 2-heptanona. Los histogramas periestímulo indicaron que: i) las neuronas hipocampales responden con un incremento en la tasa de disparo neuronal ante la estimulación amigdalina; ii) la respuesta es de mayor magnitud y duración en el grupo previamente expuesto a 2-heptanona. Dado que una sola exposición a una feromona de alarma facilita la conexión amígdala medial-hipocampo, los resultados sugieren la formación inicial de una memoria contextual relacionada con el miedo.
ABSTRACT
The semiochemicals produced by termites have been little studied compared to those of ants and bees. Among the limiting factors are the cryptic habits of termites, together with the difficulty in maintaining many species in the laboratory. The semiochemicals of Isoptera include trail, sex and alarm pheromones and a complex mixture of substances responsible for the recognition of nestmates. Although little is known about the semiochemicals of termites, available data indicate a strategy of pheromonal parsimony in the chemistry communication of these insects, i.e., the same compound is sometimes secreted by different glands, different species and for different functions.
Os semioquímicos dos cupins têm sido pouco estudados quando comparados aos de formigas e abelhas. Um dos fatores limitantes é o hábito críptico dos térmitas, aliado à dificuldade de manutenção de muitas espécies em laboratório. Entre os semioquímicos de Isoptera destacam-se os feromônios sexuais, de trilha, de alarme e uma mistura complexa de substâncias responsável pelo reconhecimento dos companheiros de ninho. Apesar de os semioquímicos dos cupins serem pouco conhecidos, os dados disponíveis indicam uma estratégia de parcimônia feromonal na comunicação química desses insetos, ou seja, algumas vezes o mesmo composto é secretado por diferentes glândulas, diferentes espécies e para diferentes funções.