Argonaute 2 is a key regulator of maternal mRNA degradation in mouse early embryos.

In mammalian early embryos, the transition from maternal to embryonic control of gene expression requires timely degradation of a subset of maternal mRNAs (MRD). Recently, zygotic genome activation (ZGA)-dependent MRD has been characterized in mouse 2-cell embryo. However, in early embryos, the dynamics of MRD is still poorly understood, and the maternal factor-mediated MRD before and along with ZGA has not been investigated. Argonaute 2 (Ago2) is highly expressed in mouse oocyte and early embryos. In this study, we showed that Ago2-dependent degradation involving RNA interference (RNAi) and RNA activation (RNAa) pathways contributes to the decay of over half of the maternal mRNAs in mouse early embryos. We demonstrated that AGO2 guided by endogenous small interfering RNAs (endosiRNAs), generated from double-stranded RNAs (dsRNAs) formed by maternal mRNAs with their complementary long noncoding RNAs (CMR-lncRNAs), could target maternal mRNAs and cooperate with P-bodies to promote MRD. In addition, we also showed that AGO2 may interact with small activating RNAs (saRNAs) to activate Yap1 and Tead4, triggering ZGA-dependent MRD. Thus, Ago2-dependent degradation is required for timely elimination of subgroups of maternal mRNAs and facilitates the transition between developmental states.

EAG and behavioral responses of Helicoverpa armigera males to volatiles from poplar leaves and their combinations with sex pheromone.

Electroantennogram (EAG) evaluation of selected compounds from wilted leaves of black poplar, Populus nigra, showed that phenyl acetaldehyde, methyl salicylate, (E)-2-hexenal elicited strong responses from male antennae of Helicoverpa armigera. When mixed with sex pheromone (Ph), some volatiles, e.g. phenyl acetaldehyde, benzyl alcohol, phenylethanol, methylsalicylate, linalool, benzaldehyde, (Z)-3-hexenol, (Z)-3-hexenylacetate, (Z)-6-nonenol, cineole, (E)-2-hexenal, and geraniol elicited stronger responses from male antennae than Ph alone. Wind tunnel bioassay demonstrated that various volatiles could either enhance or inhibit the effect of synthetic sex pheromone. (E)-2-hexenal, (Z)-3-hexenol and linalool in combination with Ph could not induce any male to land on source at all, whereas phenyl acetaldehyde, benzaldehyde, (Z)-6-nonenol and salicylaldehyde combined with Ph enhanced male response rates by 58.63%, 50.33%, 51.85% and 127.78%, respectively, compared to Ph alone. These results suggested that some volatiles should modify sex pheromone caused behavior and that some of them could possibly be used as a tool for disrupting mating or for enhancing the effect of synthetic sex pheromone in the field.

[Plant volatiles and their metabolic engineering].

Plant volatiles mainly include terpenoid, benzenoid/phenylpropanoid and fatty-acid derivatives, and they play diverse roles in plant-plant and plant-insect communications. In recent years, great progress has been made in biochemical and molecular characterization of the formation and release of these volatiles, and this make it possible to dissect their biological functions. More than 30 kinds of genes related with biosynthesis of these volatiles have been cloned. The pathways leading to synthesis of these metabolites can be controlled by enzyme activity and the substrates available as well as gene architecture. Plant volatiles can serve as attractants for specific pollinators, important cellular regulators in developmental processes and protection against environmental stress, whereas those released after herbivory or pathogen attacks can induce the expression a set of defensive genes or attraction of predators of the herbivores. An attractive prospect in this area is to design scent spectrum of plant with genetic and molecular technology. Two alternative approaches are used to genetically engineer these plant volatiles. One is based on the introduction of foreign genes encoding enzymes with activities that are missing in target plant, while the other is focused on modulating the expression of native genes.

[Tritrophic system of tree-trunkborer-insect natural enemy association].

Trunkborers, mainly bark beetles and cerambycids, are the important insect pests of forests, which can cause serious damage to forest ecosystem. Taking bark beetle and long-horned beetle as the examples, this paper summarized the research progress on the tritrophic system of tree-trunkborer-insect natural enemy association, with the past ten years research results on semiochemicals release source, active compounds identification, and release dynamics of volatiles introduced. The chemical signals selection of natural enemies and their visual function in finding hosts or preys, as well as whether there were other biological active compounds beyond this tritrophic system, which could influence the natural enemy's behaviors, were also discussed.

Effects of sublethal deltamethrin on the chemical communication system and PBAN activity of Asian corn borer, Ostrinia furnacalis (Güenee).

Topically applied sublethal doses of deltamethrin may interrupt chemical communication between the two sexes of the Asian corn borer, Ostrinia furnacalis (Güenee), by affecting the probability of calling behavior, sex pheromone titer and PBAN-like activity. At the 1st, 2nd, and 4th day of post-treatment with deltamethrin (1 ng/moth), female O. furnacalis showed 32, 36, and 46% calling probabilities of control female moths, while the sex pheromone titer of females was only 15, 20, and 25% the amount of control females, respectively. The chemical communication system was significantly affected even at the 4th day post-treatment. By injections of 1, 1/2, 1/4, and 1/8 female equivalent of brain and subesophageol ganglion homogenate of 1 ng deltamethrin-treated females into decapitated females, female pheromone production was reduced to 64, 31, 30.7, and 8.1% of that of control female moths, respectively. This result appears to indicate that sublethal deltamethrin affected the activity of the PBAN-like factor of O. furnacalis.

Enhancement of attraction to sex pheromones of Spodoptera exigua by volatile compounds produced by host plants.

We measured the effects of exposure to volatile compounds produced by host plants on the rate of capture of male Spodoptera exigua using synthetic sex pheromones. Exposure to volatile compounds stimulated strong electroantennographic responses of male S. exigua. The behavioral responses of male moths to combinations of sex pheromone and volatile compounds were tested in wind tunnel experiments. When lures were baited with synthetic sex pheromone plus benzaldehyde, phenylacetaldehyde, (Z)-3-hexenyl acetate, or linalool, respectively, the landing rate of S. exigua males was increased by 101.4%, 79.6%, 60.6%, and 34.3%, respectively, compared to sex pheromone alone. In field tests, traps baited with either pheromone + (E)-2-hexenal, pheromone + phenylacetaldehyde, pheromone + (Z)-3-hexenyl acetate, or pheromone + (Z)-3-hexenol enhanced moth catches by 38.8%, 34.6%, 24.6%, and 20.8%, respectively compared to traps baited with pheromone alone. In a second field experiment, more S. exigua males were trapped with a combination of a synthetic sex pheromone blend and several individual host plant volatiles compared to synthetic sex pheromone alone. These results suggest that some host plant volatiles enhance the orientation response of S. exigua male moths to sex pheromone sources.