insect development
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2022 ◽  
Author(s):  
David L. Denlinger

Our highly seasonal world restricts insect activity to brief portions of the year. This feature necessitates a sophisticated interpretation of seasonal changes and enactment of mechanisms for bringing development to a halt and then reinitiating it when the inimical season is past. The dormant state of diapause serves to bridge the unfavourable seasons, and its timing provides a powerful mechanism for synchronizing insect development. This book explores how seasonal signals are monitored and used by insects to enact specific molecular pathways that generate the diapause phenotype. The broad perspective offered here scales from the ecological to the molecular and thus provides a comprehensive view of this exciting and vibrant research field, offering insights on topics ranging from pest management, evolution, speciation, climate change and disease transmission, to human health, as well as analogies with other forms of invertebrate dormancy and mammalian hibernation.


Plants ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 10
Author(s):  
Kirstin Wurms ◽  
Annette Ah Chee ◽  
Kate Stannard ◽  
Rachelle Anderson ◽  
Dwayne Jensen ◽  
...  

Latania scale insect is a pest of global significance affecting kiwifruit. The sessile insect (life stage: settled crawler—mature adult) is covered with a waxy cap that protects it from topical pesticides, so increasingly, a selection of resistant cultivars and application of elicitors are being used in pest control. Thus far, the application of a salicylic acid (SA) phytohormone pathway elicitor, acibenzolar-S-methyl (ASM), has been shown to reduce insect development (as indicated by cap size) on one kiwifruit cultivar (‘Hayward’). To investigate how cultivar-associated resistance is affected by the ability to respond to different elicitors, we measured phytohormones (by LCMS) and gene expression (by qPCR and NanoString) on latania scale-tolerant ‘Hort16A’ and susceptible ‘Hayward’ kiwifruit over two seasons. Potted plants in the presence/absence of settled latania scales were treated with ASM (0.2 g/L) or methyl jasmonate (MeJA, 0.05% v/v), representing elicitors of the SA and JA signalling pathways, respectively. ‘Hort16A’ cultivar resistance to latania scale was associated with elevated expression of SA and SA-related defence genes (PR1 and two PR2 family genes) in the ASM treatment. MeJA treatments did not significantly affect insect development in ‘Hayward’ (latania scale did not survive on ‘Hort16A’) and did not correlate with phytohormone and gene expression measurements in either cultivar. ‘Hayward’ had greater concentrations than ‘Hort16A’ of inert storage forms of both SA and JA across all treatments. This information contributes to the selection of tolerant cultivars and the effective use of elicitors for control of latania scale in kiwifruit.


Author(s):  
Jingxu Guo ◽  
Ronan M. Keegan ◽  
Daniel J. Rigden ◽  
Peter T. Erskine ◽  
Steve P. Wood ◽  
...  

Insect juvenile hormones (JHs) are a family of sesquiterpenoid molecules that are secreted into the haemolymph. JHs have multiple roles in insect development, metamorphosis and sexual maturation. A number of pesticides work by chemically mimicking JHs, thus preventing insects from developing and reproducing normally. The haemolymph levels of JH are governed by the rates of its biosynthesis and degradation. One enzyme involved in JH catabolism is JH diol kinase (JHDK), which uses ATP (or GTP) to phosphorylate JH diol to JH diol phosphate, which can be excreted. The X-ray structure of JHDK from the silkworm Bombyx mori has been determined at a resolution of 2.0 Å with an R factor of 19.0% and an R free of 24.8%. The structure possesses three EF-hand motifs which are occupied by calcium ions. This is in contrast to the recently reported structure of the JHDK-like-2 protein from B. mori (PDB entry 6kth), which possessed only one calcium ion. Since JHDK is known to be inhibited by calcium ions, it is likely that our structure represents the calcium-inhibited form of the enzyme. The electrostatic surface of the protein suggests a binding site for the triphosphate of ATP close to the N-terminal end of the molecule in a cavity between the N- and C-terminal domains. Superposition with a number of calcium-activated photoproteins suggests that there may be parallels between the binding of JH diol to JHDK and the binding of luciferin to aequorin.


Author(s):  
E. P. Rybalkin ◽  
V. A. Shishkin ◽  
V. N. Opanasenko

Protection of fruit crops from pests is one of the most important tasks of gardening. In turn, the use of protective measures has both positive and negative sides, which makes the issue of improving their effectiveness one of the main ones. Having data on the estimated number of pests and the dates of the beginning of their development phases, it is possible to increase efficiency by choosing the optimal exposure measure and drawing up a more accurate schedule of protective measures. One way to determine such parameters is to use simulation. The article presents one of the approaches to constructing a mathematical model of the insect development process, which is used to build a software simulation model that allows to increase the effectiveness of protective measures of fruit crops. The article describes what is the essence of the modeled process. A mathematical model and methods for determining its parameters are presented. The required initial data for modeling are defined.


Metabolites ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 731
Author(s):  
Dimitra Papantoniou ◽  
Fredd Vergara ◽  
Alexander Weinhold ◽  
Teresa Quijano ◽  
Bekzod Khakimov ◽  
...  

Root mutualistic microbes can modulate the production of plant secondary metabolites affecting plant–herbivore interactions. Still, the main mechanisms underlying the impact of root mutualists on herbivore performance remain ambiguous. In particular, little is known about how changes in the plant metabolome induced by root mutualists affect the insect metabolome and post-larval development. By using bioassays with tomato plants (Solanum lycopersicum), we analyzed the impact of the arbuscular mycorrhizal fungus Rhizophagus irregularis and the growth-promoting fungus Trichoderma harzianum on the plant interaction with the specialist insect herbivore Manduca sexta. We found that root colonization by the mutualistic microbes impaired insect development, including metamorphosis. By using untargeted metabolomics, we found that root colonization by the mutualistic microbes altered the secondary metabolism of tomato shoots, leading to enhanced levels of steroidal glycoalkaloids. Untargeted metabolomics further revealed that root colonization by the mutualists affected the metabolome of the herbivore, leading to an enhanced accumulation of steroidal glycoalkaloids and altered patterns of fatty acid amides and carnitine-derived metabolites. Our results indicate that the changes in the shoot metabolome triggered by root mutualistic microbes can cascade up altering the metabolome of the insects feeding on the colonized plants, thus affecting the insect development.


Agronomy ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 2002
Author(s):  
Luis Carlos Martínez ◽  
Angelica Plata-Rueda ◽  
José Eduardo Serrão

The potential of insecticides that affect the growth and insect development to control Euprosterna elaeasa was evaluated. Fenoxycarb, methoxyfenozide, pyriproxyfen, and tebufenozide were assessed against E. elaeasa larvae for toxicity, survivorship, and feeding inhibition in the laboratory, and mortality in semifield conditions. Concentration–mortality bioassays demonstrated that insect growth regulators (IGRs) have a lethal effect on this insect, with pyriproxyfen (LC50 = 0.141 g L−1) being the most effective, followed by fenoxycarb (LC50 = 0.199 g L−1), methoxyfenozide (LC50 = 0.233 g L−1), and tebufenozide (LC50 = 0.259 g L−1). The survival rate was 99.8% in the control group, compared to 44.6%, 42.9%, 42.2%, and 39.5% in insects treated with pyriproxyfen, fenoxycarb, methoxyfenozide, and tebufenozide, respectively. IGRs caused feeding inhibition in E. elaeasa larvae 3 h after exposure. Furthermore, mortality in semifield conditions was similar to the results found in the laboratory. Our findings suggest that fenoxycarb, methoxyfenozide, pyriproxyfen, and tebufenozide are effective against E. elaeasa and, therefore, we confirm the potential of these IGRs for the control of this pest.


2021 ◽  
Vol 118 (35) ◽  
pp. e2101442118
Author(s):  
Yan Yang ◽  
Tujing Zhao ◽  
Zheng Li ◽  
Wenliang Qian ◽  
Jian Peng ◽  
...  

Insect development is cooperatively orchestrated by the steroid hormone ecdysone and juvenile hormone (JH). The polycomb repressive complex 2 (PRC2)–mediated histone H3K27 trimethylation (H3K27me3) epigenetically silences gene transcription and is essential for a range of biological processes, but the functions of H3K27 methylation in insect hormone action are poorly understood. Here, we demonstrate that H3K27 methylation–mediated repression of Hairy transcription in the larval prothoracic gland (PG) is required for ecdysone biosynthesis in Bombyx and Drosophila. H3K27me3 levels in the PG are dynamically increased during the last larval instar. H3K27me3 reduction induced by the down-regulation of PRC2 activity via inhibitor treatment in Bombyx or PG-specific knockdown of the PRC2 component Su(z)12 in Drosophila diminishes ecdysone biosynthesis and disturbs the larval–pupal transition. Mechanistically, H3K27 methylation targets the JH signal transducer Hairy to repress its transcription in the PG; PG-specific knockdown or overexpression of the Hairy gene disrupts ecdysone biosynthesis and developmental transition; and developmental defects caused by PG-specific Su(z)12 knockdown can be partially rescued by Hairy down-regulation. The application of JH mimic to the PG decreases both H3K27me3 levels and Su(z)12 expression. Altogether, our study reveals that PRC2-mediated H3K27 methylation at Hairy in the PG during the larval period is required for ecdysone biosynthesis and the larval–pupal transition and provides insights into epigenetic regulation of the crosstalk between JH and ecdysone during insect development.


Biomolecules ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1031
Author(s):  
Umut Toprak ◽  
Cansu Doğan ◽  
Dwayne Hegedus

Calcium (Ca2+) homeostasis is vital for insect development and metabolism, and the endoplasmic reticulum (ER) is a major intracellular reservoir for Ca2+. The inositol 1,4,5- triphosphate receptor (IP3R) and ryanodine receptor (RyR) are large homotetrameric channels associated with the ER and serve as two major actors in ER-derived Ca2+ supply. Most of the knowledge on these receptors derives from mammalian systems that possess three genes for each receptor. These studies have inspired work on synonymous receptors in insects, which encode a single IP3R and RyR. In the current review, we focus on a fundamental, common question: “why do insect cells possess two Ca2+ channel receptors in the ER?”. Through a comparative approach, this review covers the discovery of RyRs and IP3Rs, examines their structures/functions, the pathways that they interact with, and their potential as target sites in pest control. Although insects RyRs and IP3Rs share structural similarities, they are phylogenetically distinct, have their own structural organization, regulatory mechanisms, and expression patterns, which explains their functional distinction. Nevertheless, both have great potential as target sites in pest control, with RyRs currently being targeted by commercial insecticide, the diamides.


Open Biology ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 210028
Author(s):  
Ana Carolina Borella Marfil Anhê ◽  
Raquel Soares Maia Godoy ◽  
Rafael Nacif-Pimenta ◽  
Wagner Faria Barbosa ◽  
Marcus Vinicius Lacerda ◽  
...  

Rhodnius prolixus is the principal vector of Trypanosoma cruzi , the aetiological agent of Chagas disease in American countries. This insect is haematophagous during all life cycles and, to antagonize its haemostatic, inflammatory and immune systems, it secretes saliva while feeding on the vertebrate host's blood. Here, we investigated characteristic changes of the salivary glands (SG) that occur during insect development. Two pairs of lobules and ducts comprise the SG of R. prolixus . The organ's size increases over time, but the microanatomical structures are preserved during insect development. Both lobules have a single layer epithelium formed by binucleated cells, which surrounds the saliva reservoir. The principal lobule presents higher polysaccharide and total protein contents than the accessory lobe. A network of external muscle layers is responsible for organ contraction and saliva release. Apocrine, merocrine and holocrine secretion types occur in the secretory epithelium. Dopamine, serotonin and tyrosine-hydroxylase are neural-related molecules that regulate SG function both during and after feeding.


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