β-Ionone: Its Occurrence and Biological Function and Metabolic Engineering

β-Ionone is a natural plant volatile compound, and it is the 9,10 and 9′,10′ cleavage product of β-carotene by the carotenoid cleavage dioxygenase. β-Ionone is widely distributed in flowers, fruits, and vegetables. β-Ionone and other apocarotenoids comprise flavors, aromas, pigments, growth regulators, and defense compounds; serve as ecological cues; have roles as insect attractants or repellants, and have antibacterial and fungicidal properties. In recent years, β-ionone has also received increased attention from the biomedical community for its potential as an anticancer treatment and for other human health benefits. However, β-ionone is typically produced at relatively low levels in plants. Thus, expressing plant biosynthetic pathway genes in microbial hosts and engineering the metabolic pathway/host to increase metabolite production is an appealing alternative. In the present review, we discuss β-ionone occurrence, the biological activities of β-ionone, emphasizing insect attractant/repellant activities, and the current strategies and achievements used to reconstruct enzyme pathways in microorganisms in an effort to to attain higher amounts of the desired β-ionone

A Review of the Botany, Volatile Composition, Biochemical and Molecular Aspects, and Traditional Uses of <i>Laurus nobilis</i>

Laurus nobilis L. is an aromatic medicinal plant widely cultivated in many world regions. L. nobilis has been increasingly acknowledged over the years as it provides an essential contribution to the food and pharmaceutical industries and cultural integrity. The commercial value of this species derives from its essential oil, whose application might be extended to various industries. The chemical composition of the essential oil depends on environmental conditions, location, and season during which the plants are collected, drying methods, extraction, and analytical conditions. The characterization and chemotyping of L. nobilis essential oil are extremely important because the changes in composition can affect biological activities. Several aspects of the plant’s secondary metabolism, particularly volatile production in L. nobilis, are still unknown. However, understanding the molecular basis of flavor and aroma production is not an easy task to accomplish. Nevertheless, the time-limited efforts for conservation and the unavailability of knowledge about genetic diversity are probably the major reasons for the lack of breeding programs in L. nobilis. The present review gathers the scientific evidence on the research carried out on Laurus nobilis L., considering its cultivation, volatile composition, biochemical and molecular aspects, and antioxidant and antimicrobial activities

Dynamic Economic Thresholds for Insecticide Applications Against Agricultural Pests: Importance of Pest and Natural Enemy Migration

International audienceIn Integrated Pest Management programs, insecticides are applied to agricultural crops when pest densities exceed a predetermined economic threshold. Under conditions of high natural enemy density, however, the economic threshold can be increased, allowing for fewer insecticide applications. These adjustments, called ‘dynamic thresholds’, allow farmers to exploit existing biological control interactions without economic loss. Further, the ability of natural enemies to disperse from, and subsequently immigrate into, insecticide-sprayed areas can affect their biological control potential. We develop a theoretical approach to incorporate both pest and natural enemy movement across field borders into dynamic thresholds and explore how these affect insecticide applications and farmer incomes. Our model follows a pest and its specialist natural enemy over one growing season. An insecticide that targets the pest also induces mortality of the natural enemy, both via direct toxicity and reduced resource pest densities. Pest and natural enemy populations recover after spraying through within-field reproduction and by immigration from neighboring unsprayed areas. The number of insecticide applications and per-season farmer revenues are calculated for economic thresholds that are either fixed (ignoring natural enemy densities) or dynamic (incorporating them). The model predicts that using dynamic thresholds always leads to reduced insecticide application. The benefit of dynamic thresholds in reducing insecticide use is highest when natural enemies rapidly recolonize sprayed areas, and when insecticide efficacy is low. We discuss real-life situations in which monitoring of natural enemies would substantially reduce insecticide use and other scenarios where the presence of beneficial organisms may lead to threshold modifications

Production and characterization of Trichoderma asperellum chitinases and their use in synergy with Bacillus thuringiensis for lepidopteran control

Background: Despite their known negative effects on ecosystems and human health, synthetic pesticides are still largely used to control crop insect pests. Actually, the biopesticide market for insect biocontrol mainly relies on the entomopathogenic bacterium Bacillus thuringiensis (Bt). New biocontrol tools for crop protection might derive from fungi, in particular from Trichoderma spp., which are known producers of chitinases and other bioactive compounds able to negatively affect insect survival. Results: In this study, we first developed an environmentally sustainable production process for obtaining chitinases from Trichoderma asperellum ICC012. Then, we investigated the biological effects of this chitinase preparation - alone or in combination with a Bt-based product - when orally administered to two lepidopteran species. Our results demonstrate that T. asperellum efficiently produces a multi-enzymatic cocktail able to alter the chitin microfibril network of the insect peritrophic matrix, resulting in delayed development and larval death. The co-administration of T. asperellum chitinases and sublethal concentrations of Bt toxins increased larval mortality. This synergistic effect was likely due to the higher amount of Bt toxins that passed the damaged peritrophic matrix and reached the target receptors on the midgut cells of chitinase-treated insects. Conclusion: Our findings could contribute to the development of an integrated pest management technology based on fungal chitinases that increase the efficacy of Bt-based products and may mitigate the risk of Bt-resistance development. This article is protected by copyright. All rights reserved

Tuta absoluta continues to disperse in Asia: damage, ongoing management and future challenges

Since its initial detection in Turkey in 2009, the invasive destructive pest South American tomato pinworm Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) has started its new invasion journey to east and invaded most Asian countries. This pest currently causes extensive damage to tomato production and potentially threatens key production areas such as China. To provide an overview of current status of T. absoluta in Asia, we have briefly reviewed the damage and economic impacts by this pest locally and discussed why this species has spread so rapidly among the countries. Moreover, ongoing integrated pest management options are summarized in newly invaded areas with an emphasis of discussing the potential control failures by chemical insecticides. Future research efforts on developing promising management technologies are recommended. Finally, we suggest building a cross-regional network to enhance the sustainable control of this pest