Mating behavior is essential for sexual reproduction, and it is often modulated by key chemical cues.  In many moth species, males find compatible mates through the reception of sex pheromones which are released by females.  Pheromone receptors (PRs) are key elements in sensing these chemical signals.  Concurrently, male moths emit a complex blend of volatile compounds during courtship; however, the mechanisms for recognizing putative male pheromones remain poorly understood.  Here, we employed gas chromatography coupled with electroantennographic detection and mass spectrometry to analyze the volatile compounds produced by males of the cotton bollworm, Helicoverpa armigera.  Three candidate male sex pheromones were identified, with (Z)-7-dodecen-1-yl acetate (Z7-12:OAc) eliciting the most pronounced electrophysiological response in the male antenna.  The olfactory receptor neuron (ORN) ORN-a in Type A trichoid sensilla was shown to respond to Z7-12:OAc by conducting single sensillum recording (SSR) assays.  Additionally, we found that the OR13s from five Heliothinae species responded to Z7-12:OAc by using the Xenopus oocyte expression system and two-electrode voltage-clamp recording.  Our findings identified a candidate for evaluation in future behavioral studies of the poorly understood chemosensory recognition mechanisms underlying male sex pheromones.  If its relevance is supported by behavioral data, this knowledge may facilitate the design of novel olfactory regulators for effective pest control strategies involving mating disruption.

The trade-off between yield and environmental effects caused by nitrogen fertilizer application is an important issue in wheat production.  A reduction in fertile florets is one of the main reasons for the lower yields under low nitrogen application rates.  Brassinosteroids (BRs) have been found to play a role in nitrogen-induced rice spikelet degeneration.  However, whether BRs play a role in wheat floret development and the mechanisms involved are not clear.  Therefore, a nitrogen gradient experiment and exogenous spraying experiment were conducted to investigate the role and mechanism of BRs in wheat floret development under low nitrogen stress.  The results showed that as the nitrogen application decreased, the endogenous BRs content of the spikes decreased, photosynthesis weakened, and total carbon, soluble sugar and starch in the spikes decreased, leading to a reduction in the number of fertile florets.  Under low nitrogen stress, exogenous spraying of 24-epibrassinolide promoted photosynthesis, and stimulated stem fructan hydrolysis and the utilization and storage of sucrose in spikes, which directed more carbohydrates to the spikes and increased the number of fertile florets.  In conclusion, BRs mediate the effects of nitrogen fertilizer on wheat floret development, and under low nitrogen stress, foliar spraying of 24-epibrassinolide promotes the flow of carbohydrates from the stem to the spikes, alleviating wheat floret degeneration.

Aphis gossypii has become increasingly difficult to manage due to its strong insecticide resistance.  In the laboratory, we established sulfoxaflor-resistant and acetamiprid-resistant strains in two A. gossypii populations with different basal insecticide resistance levels, and evaluated the effects of basal insecticide resistance on the resistance development and cross-resistance, as well as differences in fitness.  Under the same selection pressure, Yarkant A. gossypii (with low basal insecticide resistance) evolved resistance to sulfoxaflor and acetamiprid more quickly than Jinghe A. gossypii (with high basal insecticide resistance), and the evolution of A. gossypii resistance to sulfoxaflor developed faster than acetamiprid in both Yarkant and Jinghe, Xingjiang, China.  The sulfoxaflor-resistant strains selected from Yarkant and Jinghe developed significant cross-resistance to acetamiprid, imidacloprid, thiamethoxam and pymetrozine; while the acetamiprid-resistant strains developed significant cross-resistance to sulfoxaflor, imidacloprid, thiamethoxam, pymetrozine, and chlorpyrifos.  The relative fitness of A. gossypii decreased as the resistance to sulfoxaflor and acetamiprid developed.  The relative fitness levels of the sulfoxaflor-resistant strains (Yarkant-SulR and Jinghe-SulR) were lower than those of the acetamiprid-resistant strains (Yarkant-AceR and Jinghe-AceR).  In addition, the relative fitness levels of sulfoxaflor- and acetamiprid-resistant strains were lower in Jinghe than in Yarkant.  In summary, basal insecticide resistance of A. gossypii and insecticide type affected the evolution of resistance to insecticides in A. gossypii, as well as cross-resistance to other insecticides.  The sulfoxaflor- and acetamiprid-resistant A. gossypii strains had obvious fitness costs.  The results of this work will contribute to the insecticide resistance management and integrated management of A. gossypii.

Spodoptera frugiperda is a highly destructive pest that has become a global problem due to its robust reproductive and migratory capabilities.  Transient receptor potential (TRP) channels, which constitute a vast ion channel family, play pivotal roles in sensing the external environment and maintaining internal homeostasis in insects.  TRP channels have been widely investigated for their critical roles in regulating various insect behaviors in recent years.  In this study, we identified 15 TRP gene loci encoding 26 transcripts in the genome of S. frugiperda and analyzed their expression profiles at different developmental stages.  The results revealed that S. frugiperda possesses four TRPC genes, six TRPA genes, one TRPM gene, two TRPV genes, one TRPN gene, and one TRPML gene, while a canonical TRPP is absent.  Moreover, the SfruTRPA1 was functionally characterized using the Xenopus oocyte expression system.  The results showed that SfruTRPA1 is activated by temperature increases from 20 to 45°C, and there is no significant desensitization after repeated stimuli within the same temperature range.  Additionally, SfruTRPA1 is activated by certain natural chemicals, including allyl isothiocyanate (AITC) and cinnamaldehyde (CA).  These findings provide valuable insights to the TRP genes in S. frugiperda.

The Janus kinase/signal transducers and activators of transcription (JAK/STAT) signaling pathway play a pivotal role in innate immunity.  Among invertebrates, Domeless receptors serve as the key upstream regulators of this pathway.  In our study on Bactrocera dorsalis, we identified three cytokine receptors: BdDomeless1, BdDomeless2, and BdDomeless3.  Each receptor encompasses five fibronectin-type-III-like (FN III) extracellular domains and a transmembrane domain.  Furthermore, these receptors exhibit the increased responsiveness to diverse pathogenic challenges.  Notably, only BdDomeless3 is upregulated during symbiont-like viral infections.  Moreover, silencing BdDomeless3 enhanced the infectivity of Bactrocera dorsalis cripavirus (BdCV) and B. dorsalis picorna-like virus (BdPLV), underscoring BdDomeless3’s crucial role in antiviral defense of B. dorsalis.  Following the suppression of Domeless3 expression, six antimicrobial peptide genes displayed decreased expression, potentially correlating with the rise in viral infectivity.  To our knowledge, this is the first study identifying cytokine receptors associated with the JAK/STAT pathway in tephritid flies, shedding light on the immune mechanisms of B. dorsalis.

Natural products have long been a crucial source of, or provided inspiration for new agrochemical discovery.  Naturally occurring 18β-glycyrrhetinic acid shows broad-spectrum bioactivities and is a potential skeleton for novel drug discovery.  To extend the utility of 18β-glycyrrhetinic acid for agricultural uses, a series of novel 18β-glycyrrhetinic acid amide derivatives were prepared and evaluated for their antibacterial potency.  Notably, compound 5k showed good antibacterial activity in vitro against Xanthomonas oryzae pv. oryzae (Xoo, EC₅₀=3.64 mg L^–1), and excellent protective activity (54.68%) against Xoo in vivo.  Compound 5k induced excessive production and accumulation of reactive oxygen species in the tested pathogens, resulting in damaging the bacterial cell envelope.  More interestingly, compound 5k could increase the activities of plant defense enzymes including catalase, superoxide dismutase, peroxidase, and phenylalanine ammonia lyase.  Taken together, these enjoyable results suggested that designed compounds derived from 18β-glycyrrhetinic acid showed potential for controlling intractable plant bacterial diseases by disturbing the balance of the phytopathogen’s redox system and activating the plant defense system

Passion fruit (Passiflora edulis Sims) is a vine of the Passiflora genus in the Passifloraceae family.  The extracted components include flavonoids and terpenoids, which have good anti-anxiety and anti-inflammatory effects in humans.  In this study, we analyzed the transcriptomes of four tissues of the ‘Zixiang’ cultivar using RNA-Seq, which provided a dataset for functional gene mining.  The de novo assembly of these reads generated 96 883 unigenes, among which 61 022 unigenes were annotated (62.99% yield).  In addition to its edible value, another important application of passion fruit is its medicinal value.  The flavonoids and terpenoids are mainly derivatives of luteolin, apigenin, cycloartane triterpenoid saponins and other active substances in leaf extracts.  A series of candidate unigenes in the transcriptome data that are potentially involved in the flavonoid and terpenoid synthesis pathways were screened using homology-based BLAST and phylogenetic analysis.  The results showed that the biosynthesis of triterpenoids in passion fruit comes from the branches of the mevalonate (MVA) and 2-C-methyl-D-erythritol 4-phosphate/1-deoxy-D-xylulose 5-phosphate (MEP/DOXP) pathways, which is different from the MVA pathway that is used in other fruit trees.  Most of the candidate genes were found to be highly expressed in the leaves and/or flowers.  Quantitative real-time PCR (qRT-PCR) verification was carried out and confirmed the reliability of the RNA-Seq data.  Further amplification and functional analysis of these putative unigenes will provide additional insight into the biosynthesis of flavonoids and terpenoids in passion fruit.

Identifying and selecting high-quality seeds is crucial for improving crop yield.  The purpose of this study was to improve the selection of crop seeds based on separating vital seeds from dead seeds, by predicting the potential germination ability of each seed, and thus improving seed quality.  The methods of oxygen consumption (Q) of seeds and the headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) were evaluated for identifying the viability of individual seeds.  Firstly, the oxygen consumption technique showed clear differences among the values related to respiratory characteristics for seeds that were either vital or not, and the discrimination ability of final oxygen consumption (Q₁₂₀) was achieved not only in sweet corn seeds but also in pepper and wheat seeds.  Besides, Q_t was established as a new variable to shorten the measuring process in the Q2 (oxygen sensor) procedure, which was significantly related to the viability of individual seeds.  To minimize seed damage during measurement, the timing for viability evaluation was pinpointed at the 12, 6 and 9 h for pepper, sweet corn, and wheat seeds based on the new variables concerning oxygen consumption (i.e., Q₁₂, Q₆ and Q₉, respectively).  The accuracies of viability prediction were 91.9, 97.7 and 96.2%, respectively.  Dead seeds were identified and hence discarded, leading to an enhancement in the quality of the seed lot as indicated by an increase in germination percentage, from 86.6, 90.9, and 53.8% to all at 100%.  We then used the HS-GC-IMS to determine the viability of individual sweet corn seeds, noting that corn seed has a heavier weight so the volatile gas components are more likely to be detected.  A total of 48 chromatographic peaks were identified, among which 38 target compounds were characterized, including alcohols, aldehydes, acids and esters.  However, there were no significant differences between the vital and dead seeds, due to the trace amount volatile composition differences among the individual seeds.  Furthermore, a PCA based on the signal intensities of the target volatile compounds obtained was found to lose its effectiveness, as it was unable to distinguish those two types of sweet corn seeds.  These strategies can provide a reference for the rapid detection of single seed viability.

Flesh firmness (FF) is an important and complex trait for melon breeders and consumers.  However, the genetic mechanism underlying FF is unclear.  Here, a soft fruit melon (P5) and a hard fruit melon (P10) were crossed to generate F₂, and the FF and fruit-related traits were recorded for two years.  By performing quantitative trait locus (QTL) specific-locus amplified fragment (SLAF) (QTL-SLAF) sequencing and molecular marker-linkage analysis, 112 844 SLAF markers were identified, and 5 919 SNPs were used to construct a genetic linkage map with a total genetic distance of 1 356.49 cM.  Ten FF- and fruit-related QTLs were identified.  Consistent QTLs were detected for fruit length (FL) and fruit diameter (FD) in both years, and QTLs for single fruit weight (SFW) were detected on two separate chromosomes in both years.  For FF, the consistent major locus (ff2.1) was located in a 0.17-Mb candidate region on chromosome 2.  Using 429 F₂ individuals derived from a cross between P5 and P10, we refined the ff2.1 locus to a 28.3-kb region harboring three functional genes.  These results provide not only a new candidate QTL for melon FF breeding but also a theoretical foundation for research on the mechanism underlying melon gene function.