Omics approaches to study juvenile hormone synthesis

Genome-wide analysis reveals transcriptional and translational changes during diapause of the Asian corn borer (Ostrinia furnacalis)

BACKGROUND

Diapause, a pivotal phase in the insect life cycle, enables survival during harsh environmental conditions. Unraveling the gene expression profiles of the diapause process helps uncover the molecular mechanisms that underlying diapause, which is crucial for understanding physiological adaptations. In this study, we utilize RNA-seq and Ribo-seq data to examine differentially expressed genes (DEGs) and translational efficiency during diapause of Asian corn borer (Ostrinia furnacalis, ACB).

RESULTS

Our results unveil genes classified as "forwarded", "exclusive", "intensified", or "buffered" during diapause, shedding light on their transcription and translation regulation patterns. Furthermore, we explore the landscape of lncRNAs (long non-coding RNAs) during diapause and identify differentially expressed lncRNAs, suggesting their roles in diapause regulation. Comparative analysis of different types of diapause in insects uncovers shared and unique KEGG pathways. While shared pathways highlight energy balance, exclusive pathways in the ACB larvae indicate insect-specific adaptations related to nutrient utilization and stress response. Interestingly, our study also reveals dynamic changes in the HSP70 gene family and proteasome pathway during diapause. Manipulating HSP protein levels and proteasome pathway by HSP activator or inhibitor and proteasome inhibitor affects diapause, indicating their vital role in the process.

CONCLUSIONS

In summary, these findings enhance our knowledge of how insects navigate challenging conditions through intricate molecular mechanisms.

Stereoselective synthesis of (E)-α,β-unsaturated esters: triethylamine-catalyzed allylic rearrangement of enol phosphates

α,β-Unsaturated esters are key structural motifs widely distributed in various biologically active molecules, and their Z/E-stereoselective synthesis has always been considered highly attractive in organic synthesis. Herein, we present a >99% (E)-stereoselective one-pot synthetic approach towards β-phosphoroxylated α,β-unsaturated esters via a mild trimethylamine-catalyzed 1,3-hydrogen migration of the corresponding unconjugated intermediates derived from the solvent-free Perkow reaction between low-cost 4-chloroacetoacetates and phosphites. Versatile β,β-disubstituted (E)-α,β-unsaturated esters were thus afforded with full (E)-stereoretentivity by cleavage of the phosphoenol linkage via Negishi cross-coupling. Moreover, a stereoretentive (E)-rich mixture of a α,β-unsaturated ester derived from 2-chloroacetoacetate was obtained and both isomers were easily afforded in one operation.

Aggregation pheromone 4-vinylanisole promotes the synchrony of sexual maturation in female locusts

Reproductive synchrony generally occurs in various group-living animals. However, the underlying mechanisms remain largely unexplored. The migratory locust, Locusta migratoria, a worldwide agricultural pest species, displays synchronous maturation and oviposition when forms huge swarm. The reproductive synchrony among group members is critical for the maintenance of locust swarms and population density of next generation. Here, we showed that gregarious female locusts displayed more synchronous sexual maturation and oviposition than solitarious females and olfactory deficiency mutants. Only the presence of gregarious male adults can stimulate sexual maturation synchrony of female adults. Of the volatiles emitted abundantly by gregarious male adults, the aggregation pheromone, 4-vinylanisole, was identified to play key role in inducing female sexual maturation synchrony. This maturation-accelerating effect of 4-vinylanisole disappeared in the females of Or35^-/- lines, the mutants of 4-vinylanisole receptor. Interestingly, 4-vinylanisole displayed a time window action by which mainly accelerates oocyte maturation of young females aged at middle developmental stages (3–4 days post adult eclosion). We further revealed that juvenile hormone/vitellogenin pathway mediated female sexual maturation triggered by 4-vinylanisole. Our results highlight a ‘catch-up’ strategy by which gregarious females synchronize their oocyte maturation and oviposition by time-dependent endocrinal response to 4-vinylanisole, and provide insight into reproductive synchrony induced by olfactory signal released by heterosexual conspecifics in a given group.

Since 2019, a plague of flying insects known as migratory locusts has been causing extensive damage to crops in East Africa. Migratory locusts sometimes live a solitary lifestyle but, if environmental conditions allow, they form large groups containing millions of individuals known as swarms that are responsible for causing locust plagues.Locusts are able to maintain such large swarms because they can aggregate and synchronize.

When they live in swarms, individual locusts produce odors that are sensed by other individuals in the group. For example, an aggregation pheromone, called 4-vinylanisole, is known to help keep large groups of locusts together. However, it is less clear how odors synchronize the reproductive cycles of the females in a swarm so that they are ready to mate with males and lay their eggs at the same time.

To address this question, Chen et al. examined when female locusts reached sexual maturity after they were exposed to odors produced by other locusts living alone or in groups. The experiments found that only 4-vinylanisole, which was abundantly released by adult male locusts living in groups, stimulated female locusts to reach sexual maturity at the same time. This odor increased the levels of a hormone known as juvenile hormone in less-developed females to help them reach sexual maturity sooner.

These findings demonstrate that when migratory locusts are living in swarms, male locusts promote the female locusts to reach sexual maturity at the same time by promoting less-developed females to ‘catch up’ with other females in the group. A next step will be to investigate the neural and molecular mechanisms underlying the ‘catch up’ effect induced by 4-vinylanisole.

Transcriptomic analysis of Bombyx mori corpora allata with comparison to prothoracic glands in the final instar larvae

The corpus allatum (CA) is an endocrine organ of insects that synthesizes juvenile hormone (JH). Yet little is known regarding the global gene expression profile for the CA, although JH signaling pathway has been well-studied in insects. Here, we report the availability of the transcriptome resource of the isolated CA from the final (fifth) instar larvae of the silkworm, Bombyx mori when the JH titer is low. We also compare it with prothoracic gland (PG) that produces the precursor of 20-hydroxyecdysone (20E), to find some common features in the JH and 20E related genes between the two organs. A total of 17,262 genes were generated using a combination of genome-guided assembly and annotation, in which 10,878 unigenes were enriched in 58 Gene Ontology terms, representing almost all expressed genes in the CA of the 5th instar larvae of B. mori. Transcriptome analysis confirmed that gene for Torso, the receptor of prothoracicotropic hormone (PTTH), is present in the PG but not in the CA. Transcriptome comparison and quantitative real time-PCR indicated that 11 genes related to JH biosynthesis and regulation and six genes for 20E are expressed in both the CA and PG, suggesting that the two organs may cross talk with each other through these genes. The temporal expression profiles of the two genes for the multifunctional neurohormonal factor sericotropin precursor and the uncharacterized protein LOC114249572, the most abundant in the CA and PG transcriptomes respectively, suggested that they might play important roles in the JH and 20E biosynthesis. The present work provides new insights into the CA and PG.

Two Undervalued Functions of the Golgi Apparatus: Removal of Excess Ca2+ and Biosynthesis of Farnesol-Like Sesquiterpenoids, Possibly as Ca2+-Pump Agonists and Membrane "Fluidizers-Plasticizers"

The extensive literature dealing with the Golgi system emphasizes its role in protein secretion and modification, usually without specifying from which evolutionary ancient cell physiological necessity such secretion originated. Neither does it specify which functional requirements the secreted proteins must meet. From a reinterpretation of some classical and recent data gained mainly, but not exclusively, from (insect) endocrinology, the view emerged that the likely primordial function of the rough endoplasmic reticulum (RER)–Golgi complex in all eukaryotes was not the secretion of any type of protein but the removal of toxic excess Ca²⁺ from the cytoplasm. Such activity requires the concurrent secretion of large amounts of Ca²⁺-carrying/transporting proteins acting as a micro-conveyor belt system inside the RER–Golgi. Thus, (fitness increasing) protein secretion is subordinate to Ca²⁺ removal. Milk with its high content of protein and Ca²⁺ (60–90 mM vs. 100 nM in unstimulated mammary gland cells) is an extreme example. The sarco(endo)plasmatic reticulum Ca²⁺-ATPases (SERCAs) and SPCA1a Ca²⁺/Mn²⁺ transport ATPases are major players in Ca²⁺ removal through the Golgi. Both are blocked by the sesquiterpenoid thapsigargin. This strengthens the hypothesis (2014) that endogenous farnesol-like sesquiterpenoids (FLSs) may act as the long sought for but still unidentified agonist(s) for Ca²⁺-pumps in both the ER and Golgi. A second putative function also emerges. The fusion of both the incoming and outgoing transport vesicles, respectively, at the cis- and trans- side of Golgi stacks, with the membrane system requiring high flexibility and fast self-closing of the involved membranes. These properties may—possibly partially—be controlled by endogenous hydrophobic membrane “fluidizers” for which FLSs are prime candidates. A recent reexamination of unexplained classical data suggests that they are likely synthesized by the Golgi itself. This game-changing hypothesis is endorsed by several arguments and data, some of which date from 1964, that the insect corpus allatum (CA), which is the major production site of farnesol-esters, has active Golgi systems. Thus, in addition to secreting FLS, in particular juvenile hormone(s), it also secretes a protein(s) or peptide(s) with thus far unknown function. This paper suggests answers to various open questions in cell physiology and general endocrinology.