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"Insects Adaptation."
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The whole genome sequence of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), reveals insights into the biology and adaptive evolution of a highly invasive pest species
Background
The Mediterranean fruit fly (medfly),
Ceratitis capitata
, is a major destructive insect pest due to its broad host range, which includes hundreds of fruits and vegetables. It exhibits a unique ability to invade and adapt to ecological niches throughout tropical and subtropical regions of the world, though medfly infestations have been prevented and controlled by the sterile insect technique (SIT) as part of integrated pest management programs (IPMs). The genetic analysis and manipulation of medfly has been subject to intensive study in an effort to improve SIT efficacy and other aspects of IPM control.
Results
The 479 Mb medfly genome is sequenced from adult flies from lines inbred for 20 generations. A high-quality assembly is achieved having a contig N50 of 45.7 kb and scaffold N50 of 4.06 Mb. In-depth curation of more than 1800 messenger RNAs shows specific gene expansions that can be related to invasiveness and host adaptation, including gene families for chemoreception, toxin and insecticide metabolism, cuticle proteins, opsins, and aquaporins. We identify genes relevant to IPM control, including those required to improve SIT.
Conclusions
The medfly genome sequence provides critical insights into the biology of one of the most serious and widespread agricultural pests. This knowledge should significantly advance the means of controlling the size and invasive potential of medfly populations. Its close relationship to
Drosophila
, and other insect species important to agriculture and human health, will further comparative functional and structural studies of insect genomes that should broaden our understanding of gene family evolution.
Journal Article
Plant Secondary Metabolites as Defense Tools against Herbivores for Sustainable Crop Protection
Plants have evolved several adaptive strategies through physiological changes in response to herbivore attacks. Plant secondary metabolites (PSMs) are synthesized to provide defensive functions and regulate defense signaling pathways to safeguard plants against herbivores. Herbivore injury initiates complex reactions which ultimately lead to synthesis and accumulation of PSMs. The biosynthesis of these metabolites is regulated by the interplay of signaling molecules comprising phytohormones. Plant volatile metabolites are released upon herbivore attack and are capable of directly inducing or priming hormonal defense signaling pathways. Secondary metabolites enable plants to quickly detect herbivore attacks and respond in a timely way in a rapidly changing scenario of pest and environment. Several studies have suggested that the potential for adaptation and/or resistance by insect herbivores to secondary metabolites is limited. These metabolites cause direct toxicity to insect pests, stimulate antixenosis mechanisms in plants to insect herbivores, and, by recruiting herbivore natural enemies, indirectly protect the plants. Herbivores adapt to secondary metabolites by the up/down regulation of sensory genes, and sequestration or detoxification of toxic metabolites. PSMs modulate multi-trophic interactions involving host plants, herbivores, natural enemies and pollinators. Although the role of secondary metabolites in plant-pollinator interplay has been little explored, several reports suggest that both plants and pollinators are mutually benefited. Molecular insights into the regulatory proteins and genes involved in the biosynthesis of secondary metabolites will pave the way for the metabolic engineering of biosynthetic pathway intermediates for improving plant tolerance to herbivores. This review throws light on the role of PSMs in modulating multi-trophic interactions, contributing to the knowledge of plant-herbivore interactions to enable their management in an eco-friendly and sustainable manner.
Journal Article
Corpse flowers smell nasty!
The huge corpse flower rarely blooms. When it does, it gives off a strong smellthe smell of a rotting corpse! The gross smell has a purpose, however. Readers learn that the stink of the corpse flower has everything to do with a main subject of the science curriculum: pollination. Other science topics covered include plant life cycles and structures. Fact boxes add even more intriguing information about this weird plant while full-color photographs offer readers an up-close look at a unique flower.
Book
Enzyme-mediated adaptation of herbivorous insects to host phytochemicals
The review comprehensively explores factors influencing enzyme activities in insects and their implications in defense against toxicants. It encompasses a diverse array of enzymes involved in metabolizing synthetic chemicals, emphasizing their dynamic regulation. Key factors affecting enzyme activities, such as external and internal influences, are discussed, shedding light on the intricate regulatory mechanisms. The inhibitory effects of various compounds on insect GST activity are thoroughly examined, providing insights into potential avenues for insect control. The implications of insect defenses against toxicants are elucidated, emphasizing the complexity of plant–insect interactions. The review delves into the evolutionary adaptations of insects to plant defense mechanisms, highlighting the role of enzymes like thioglucosidase and myrosinase in detoxifying glucosinolates. The co-evolutionary dynamics between insects and plants, particularly in the Brassicaceae family, are explored, underscoring the intricate biochemical strategies employed by both parties. Additionally, the review addresses the challenges associated with developing pest-resistant crop plants through traditional breeding or genetic engineering. It discusses the need for a nuanced approach, considering the adaptability of insects to various toxicants and the potential drawbacks of repeated exposures. The success of chemical plant defenses, particularly monoterpene synthesis in pine trees, is noted, along with the distinctive biodegradability of plant metabolites. The review provides a thorough examination of the mechanisms underlying insect responses to toxic plant metabolites, offering valuable insights into the dynamic interplay between insects and plants. It suggests potential targets for insect control programs and highlights the importance of understanding the co-evolutionary processes that shape these interactions.
Graphical abstract
Journal Article
Evidence for a gut microbial community conferring adaptability to diet quality and temperature stressors in phytophagous insects: the melon fruit fly Zeugodacus cucurbitae (Diptera: Tephritidae) as a case study
Background
The high invasiveness of phytophagous insects is related to their adaptability to various environments, that can be influenced by their associated microbial community. Microbial symbionts are known to play a key role in the biology, ecology, and evolution of phytophagous insects, but their abundance and diversity are suggested to be influenced by environmental stressors. In this work, using 16 S rRNA metabarcoding we aim to verify (1) if laboratory rearing affects microbial symbiont communities of
Zeugodacus cucurbitae
females, a cosmopolitan pest of cucurbitaceous crops (2) if temperature, diet quality, and antibiotic treatments affect microbial symbiont communities of both laboratory and wild populations, and (3) if changes in microbial symbiont communities due to temperature, diet and antibiotic affect longevity and fecundity of
Z. cucurbitae
.
Results
The results showed that microbial diversity, particularly the β-diversity was significantly affected by insect origin, temperature, diet quality, and antibiotic treatment. The alteration of gut microbial symbionts, specifically Enterobacteriaceae, was associated with low fecundity and longevity of
Z. cucurbitae
females feeding on optimal diet only. Fecundity reduction in antibiotic treated females was more pronounced when flies were fed on a poor diet without protein.
Conclusions
our study proves the relationship between gut microbiome and host fitness under thermal and diet fluctuation highlighting the importance of microbial community in the adaptation of
Z. cucurbitae
to environmental stress.
Clinical trial number
Not applicable.
Journal Article
Protease Inhibitors: An Induced Plant Defense Mechanism Against Herbivores
Plants have evolved with various effective mechanisms to defend themselves against herbivores, and one such mechanism is the production of protease inhibitors that disrupt digestion of the insects. Plant protease inhibitors (PPIs) interact with the target proteases of the insect gut, forming an enzyme–inhibitor complex that impairs normal enzymatic activity, leading to indigestion, reduced food intake, retarded growth, reproduction abnormalities, and sometimes mortality of the insect. Insects responses to these anti-nutritional compounds through remarkable physiological adaptations rendering this vast array of PPIs ineffective. Several molecular and biotechnological tools enable us to modify the expression of desired genes. CRISPR-Cas tools could cause complete knock-out of the gene, and RNA interference can cause gene knock-down. Transgenic plants overexpressing highly efficient PI genes are being developed for the management of crop pests. Although few, the reports of marginal detrimental effects of PPI-transgenic plants on non-target beneficial arthropods should be taken into consideration. Research suggests that insect-gut-associated microbes can affect insect protease levels or elicit plant defense responses and play a significant role in changing the dynamics of plant–insect interaction. Knowledge of protease gene regulation in herbivore insects can be used to deploy PPIs for the development of effective and alternate pest management strategies.
Journal Article
Evolutionary Recruitment of a Flavin-Dependent Monooxygenase for the Detoxification of Host Plant-Acquired Pyrrolizidine Alkaloids in the Alkaloid-Defended Arctiid Moth Tyria jacobaeae
Larvae of Tyria jacobaeae feed solely upon the pyrrolizidine alkaloid-containing plant Senecio jacobaea. Ingested pyrrolizidine alkaloids (PAs), which are toxic to unspecialized insects and vertebrates, are efficiently N-oxidized in the hemolymph of T. jacobaeae by senecionine N-oxygenase (SNO), a flavin-dependent monooxygenase (FMO) with a high substrate specificity for PAs. Peptide microsequences obtained from purified T. jacobaeae SNO were used to clone the corresponding cDNA, which was expressed in active form in Escherichia coli. T. jacobaeae SNO possesses a signal peptide characteristic of extracellular proteins, and it belongs to a large family of mainly FMO-like sequences of mostly unknown function, including two predicted Drosophila melanogaster gene products. The data indicate that the gene for T. jacobaeae SNO, highly specific for toxic pyrrolizidine alkaloids, was recruited from a preexisting insect-specific FMO gene family of hitherto unknown function. The enzyme allows the larvae to feed on PA-containing plants and to accumulate predation-deterrent PAs in the hemolymph.
Journal Article
Population expansion and genomic adaptation to agricultural environments of the soybean looper, Chrysodeixis includens
Evolutionary studies of insect pests improve our ability to anticipate problems in agricultural ecosystems, such as pest outbreaks, control failures, or expansions of the host range. Here, we investigated the mechanisms underlying the evolutionary processes behind the recent census size expansion and local adaptation of Chrysodeixis includens. First, we sequenced mitochondrial markers to conduct a phylogeographic investigation of C. includens historical processes. Then, we combined a de novo genotyping‐by‐sequencing approach with a study of agricultural landscapes to uncover recent processes of adaptation. Primarily, we found low genetic diversity across all markers and clear indications of a recent demographic expansion. We also found a lack of significant isolation by distance (IBD), and weak or absent genetic structure considering geographic locations. However, we did find initial signs of population differentiation that were associated with host plant types (i.e., soybean and cotton). Agricultural landscape attributes, including soybean crops, were significantly associated with putative markers under positive selection. Moreover, positive selection associated with host differentiation was putatively linked to digestive enzymes. This study showed how landscape composition and host plants can affect the evolutionary process of agricultural pest insects such as C. includens.
Journal Article