A PLA2 deletion mutant using CRISPR/Cas9 coupled to RNASeq reveals insect immune genes associated with eicosanoid signaling.

Eicosanoids mediate insect immune responses and synthesized by the catalytic activity of phospholipase A2 (PLA2). A uniquely encoded secretory PLA2 (sPLA2) is associated with immune responses of a lepidopteran insect, Spodoptera exigua. Its deletion mutant was generated using a CRISPR/Cas9 genome editing technology. Both wild and mutant lines were then immune-challenged, and the resulting transcripts were compared with their naïve transcripts by RNASeq using the Illumina-HiSeq platform. In total, 12,878 unigenes were further analyzed by differentially expressed gene tools. Over 69% of the expressed genes in S. exigua larvae are modulated in their expression levels by eicosanoids, recorded from CRISPR/Cas9 mutagenesis against an eicosanoid-synthetic gene, Se-sPLA2. Further, about 36% of the immune-associated genes are controlled by the eicosanoids in S. exigua. Indeed, the deletion mutant suffered significant immunosuppression in both cellular and humoral responses in response to bacterial challenge as well as severely reduced developmental and reproductive potentials.

Evaluating the impact of hot water killing larvae on gene expression using the transformer gene in Cochliomyia macellaria (Diptera: Calliphoridae).

In forensic entomology, determining the age of a larva from a body to estimate time since death is commonly performed through the measurement of a physical trait. Gene expression has been studied as an alternative age estimation approach, but the storage conditions required for these studies are different than those used in forensic entomological casework. Studies analyzing gene expression prioritize the preservation of RNA, which requires fresh tissue and ultra-cold storage. Casework, in contrast, utilizes hot water killing specimens that may not be analyzed for a long period after collection. In the current study, the impact of hot water killing on gene expression was assessed for larval samples of the forensically important blow fly, Cochliomyia macellaria. Successful amplification of the sex-determining gene, transformer, was tested across larvae ranging in size from 3.22 to 16.85 mm in length after storage times of 1-2 weeks, 4-5 weeks, and 8-9 weeks at 4°C in RNAlater. Larvae hot water killed were processed in tandem with larvae stored live to allow for a direct assessment of the impact of boiling on gene expression. As expected, the transformer gene was successfully amplified in all larvae stored live. For the hot water-killed larvae, the success rate was only slightly lower, with 3 out of 75 larvae not generating a sex-specific band pattern. The results show gene expression can be used for hot water-killed samples, though future work across different genes, species, and extending to quantitative gene expression methods is needed.

Reference genes to study the sex-biased expression of genes regulating Drosophila metabolism.

Sex is an important variable in biology. Notable differences have been observed between male and female Drosophila in regulation of metabolism, in response to nutritional challenges, and in phenotypes relevant for obesity and metabolic disorders. The differences between males and females can be expected to result from differences in gene expression. We observed that expression levels of reference genes commonly used for normalization of qRT-PCR results such as GAPDH, ß-actin, and 18SrRNA, show prominent sexual dimorphism. Since this will impact relative expression and conclusions related to that, we performed a systematic analysis of candidate reference genes with the objective of identifying reference genes with stable expression in male and female Drosophila. These reference genes (LamCa, ßTub60D and ßTub97EF) were then used to assess sex-specific differences in expression of metabolism associated genes. Additionally, we evaluated the utility of these reference genes following a nutritional challenge and showed that LamCa and ßtub97EF are stably expressed between sexes and under different nutritional conditions and are thus suitable as reference genes. Our results highlight the importance of evaluating the stability of reference genes when sex-specific differences in gene expression are studied, and identify structural genes as a category worth exploring as reference genes in other species. Finally, we also uncovered hitherto unknown sexually dimorphic expression of a number of metabolism-associated genes, information of interest to others working in the field of metabolic disorders.

Identification of chemosensory genes in the stingless bee Tetragonisca fiebrigi.

Reception of chemical information from the environment is crucial for insects' survival and reproduction. The chemosensory reception mainly occurs by the antennae and mouth parts of the insect, when the stimulus contacts the chemoreceptors located within the sensilla. Chemosensory receptor genes have been well-studied in some social hymenopterans such as ants, honeybees, and wasps. However, although stingless bees are the most representative group of eusocial bees, little is known about their odorant, gustatory, and ionotropic receptor genes. Here, we analyze the transcriptome of the proboscis and antennae of the stingless bee Tetragonisca fiebrigi. We identified and annotated 9 gustatory and 15 ionotropic receptors. Regarding the odorant receptors, we identified 204, and we were able to annotate 161 of them. In addition, we compared the chemosensory receptor genes of T. fiebrigi with those annotated for other species of Hymenoptera. We found that T. fiebrigi showed the largest number of odorant receptors compared with other bees. Genetic expansions were identified in the subfamilies 9-exon, which was also expanded in ants and paper wasps; in G02A, including receptors potentially mediating social behavior; and in GUnC, which has been related to pollen and nectar scent detection. Our study provides the first report of chemosensory receptor genes in T. fiebrigi and represents a resource for future molecular and physiological research in this and other stingless bee species.

Identification and sex expression profiles of candidate chemosensory genes from Atherigona orientalis via the antennae and leg transcriptome analysis.

Atherigona orientalis Schiner (1868) is an acknowledged agricultural pest owing to its feeding habits and breeding locations. This insect is a tropical and subtropical pest in fruits and vegetables, in which >50 varieties of fruits and vegetables in 26 families, such as Capsicum annuum, Lycopersicon esculentum, and Cucumis melo have been attacked. Moreover, A. orientalis may also develop in rotten crops and feces or insect carcasses, which are also considered one kind of sanitary pest and medical insect. At present, the invasion ranges of A. orientalis are still increasing and more preventive and management measures are to be processed. To gain a better understanding of the molecular mechanisms involved in olfactory reception in A. orientalis, the transcriptome of male and female antennae and legs was systematically analyzed. In total, 131 chemosensory-related genes, including 63 odorant receptors (ORs), 20 gustatory receptors (GRs), 18 ionotropic receptors (IRs), 27 odorant binding proteins (OBPs), 1 chemosensory protein (CSP), and 2 sensory neuron membrane proteins (SNMPs), were identified. The analysis focused on obtaining expression information of candidate olfactory genes at the transcriptomic level by examining the differentially expressed genes (DEGs) in all samples. Totally, 41 DEGs were identified between male antennae (MA) and female antennae (FA), including 32 ORs, 5 OBPs, 1 IR, 2 GRs and 1 SNMP. In MA versus male legs (ML), 78 DEGs were identified (45 ORs, 18 OBPs, 6 GRs, 6 IRs, 1 CSP and 2 SNMPs). In FA and female legs (FL), 96 DEGs were identified (51 ORs, 21 OBPs, 9 GRs, 12 IRs, 1 CSP and 2 SNMPs). For ML and FL, 3 DEGs were identified, including 2 ORs and 1 SNMP. Our results supplement valuable insights for future research on the chemoreception mechanisms in A. orientalis.

Adaptive introgression of a visual preference gene.

Visual preferences are important drivers of mate choice and sexual selection, but little is known of how they evolve at the genetic level. In this study, we took advantage of the diversity of bright warning patterns displayed by Heliconius butterflies, which are also used during mate choice. Combining behavioral, population genomic, and expression analyses, we show that two Heliconius species have evolved the same preferences for red patterns by exchanging genetic material through hybridization. Neural expression of regucalcin1 correlates with visual preference across populations, and disruption of regucalcin1 with CRISPR-Cas9 impairs courtship toward conspecific females, providing a direct link between gene and behavior. Our results support a role for hybridization during behavioral evolution and show how visually guided behaviors contributing to adaptation and speciation are encoded within the genome.

The genome of the blind bee louse fly reveals deep convergences with its social host and illuminates Drosophila origins.

Social insects' nests harbor intruders known as inquilines,1 which are usually related to their hosts.2,3 However, distant non-social inquilines may also show convergences with their hosts,4,5 although the underlying genomic changes remain unclear. We analyzed the genome of the wingless and blind bee louse fly Braula coeca, an inquiline kleptoparasite of the western honey bee, Apis mellifera.6,7 Using large phylogenomic data, we confirmed recent accounts that the bee louse fly is a drosophilid8,9 and showed that it had likely evolved from a sap-breeder ancestor associated with honeydew and scale insects' wax. Unlike many parasites, the bee louse fly genome did not show significant erosion or strict reliance on an endosymbiont, likely due to a relatively recent age of inquilinism. However, we observed a horizontal transfer of a transposon and a striking parallel evolution in a set of gene families between the honey bee and the bee louse fly. Convergences included genes potentially involved in metabolism and immunity and the loss of nearly all bitter-tasting gustatory receptors, in agreement with life in a protective nest and a diet of honey, pollen, and beeswax. Vision and odorant receptor genes also exhibited rapid losses. Only genes whose orthologs in the closely related Drosophila melanogaster respond to honey bee pheromone components or floral aroma were retained, whereas the losses included orthologous receptors responsive to the anti-ovarian honey bee queen pheromones. Hence, deep genomic convergences can underlie major phenotypic transitions during the evolution of inquilinism between non-social parasites and their social hosts.

FlyBase: updates to the Drosophila genes and genomes database.

FlyBase (flybase.org) is a model organism database and knowledge base about Drosophila melanogaster, commonly known as the fruit fly. Researchers from around the world rely on the genetic, genomic, and functional information available in FlyBase, as well as its tools to view and interrogate these data. In this article, we describe the latest developments and updates to FlyBase. These include the introduction of single-cell RNA sequencing data, improved content and display of functional information, updated orthology pipelines, new chemical reports, and enhancements to our outreach resources.

Stability evaluation of candidate reference genes for real-time qPCR normalization in Rhyzopertha dominica (Coleoptera: Bostrycidae).

Rhyzopertha dominica is a serious stored grain insect pest around the world. Real-time quantitative polymerase chain reaction (RT-qPCR) is a widely used experimental method in molecular biology for detecting the expression of target genes. As appropriate reference genes are essential for normalizing gene expression, the selection of suitable reference genes is the basis of RT-qPCR experiments. In this study, the expression profiles of 7 candidate reference genes of rps3, rps6, rps13, actin, gadph, tubulin, and 18S rRNA were analyzed under 4 different experimental conditions. The expression stability of candidate genes was evaluated using the ΔCt, GeNorm, BestKeeper, NormFinder, and RefFinder methods. The results revealed that different reference genes were suitable for various experiments. Specifically, rps3 and rps6 were appropriate for the developmental stages and all samples: 18S rRNA and rps13 for temperature-related experiments, actin and rps6 for sex-related experiments, and rps6 and gadph for starvation stress. Our results lay essential groundwork for the normalization of RT-qPCR analyses and contribute to genomic and gene functional research of R. dominica.

[Analyzing the evolution of insect TMED gene and the expression pattern of silkworm TMED gene].

Transmembrane emp24 domain (TMED) gene is closely related to immune response, signal transduction, growth and disease development in mammals. However, only the Drosophila TMED gene has been reported on insects. We identified the TMED family genes of silkworm, Tribolium castaneum, tobacco moth and Italian bee from their genomes, and found that the TMED family gene composition patterns of one α-class, one ß-class, one δ-class and several γ-classes arose in the common ancestor of pre-divergent Hymenoptera insects, while the composition of Drosophila TMED family members has evolved in a unique pattern. Insect TMED family γ-class genes have evolved rapidly, diverging into three separate subclasses, TMED6-like, TMED5-like and TMED3-like. The TMED5-like gene was lost in Hymenoptera, duplicated in the ancestors of Lepidoptera and duplicated in Drosophila. Insect TMED protein not only has typical structural characteristics of TMED, but also has obvious signal peptide. There are seven TMED genes in silkworm, distributed in six chromosomes. One of seven is single exon and others are multi-exons. The complete open reading frame (ORF) sequences of seven TMED genes of silkworm were cloned from larval tissues and registered in GenBank database. BmTMED1, BmTMED2 and BmTMED6 were expressed in all stages and tissues of the silkworm, and all genes were expressed in the 4th and 5th instar and silk gland of the silkworm. The present study revealed the composition pattern of TMED family members, their γ class differentiation and their evolutionary history, providing a basis for further studies on TMED genes in silkworm and other insects.

[Genome-wide identification of the BmAKR gene family in the silkworm (Bombyx mori) and their expression analysis in diapause eggs and nondiapause eggs].

The aldo-keto reductase super family (AKRs) has a wide range of substrate specificity. However, the systematic identification of insect AKR gene family members has not been reported. In this study, bioinformatics methods were used to predict the phylogenetic evolution, physical and chemical properties, chromosome location, conserved motifs, and gene structure of AKR family members in Bombyx mori (BmAKR). Transcriptome data or quantitative real time polymerase chain reaction (qRT-PCR) were used to analyze the expression level of BmAKR genes during different organizational periods and silkworm eggs in different developmental states. Moreover, Western blotting was used to detect the expression level of the BmAKR in silkworm eggs. The results showed that 11 BmAKR genes were identified. These genes were distributed on 4 chromosomes of the silkworm genome, all of which had the (α/ß) 8-barrel motif, and their physical and chemical characteristics were relatively similar. Phylogenetic analysis showed that the BmAKR genes could be divided into 2 subgroups (AKR1 and AKR2). Transcriptome data analysis showed that the expression of BmAKR genes were quite different in different tissues and periods. Moreover, the expression analysis of BmAKR genes in silkworm eggs showed that some genes were expressed significantly higher in nondiapause eggs than in diapause eggs; but another gene, BmAKR1-1, was expressed significantly higher in diapause eggs than in nondiapause eggs. The detection of protein level found that the difference trend of BmAKR1-1 in diapause eggs and non-diapause eggs was consistent with the results of qRT-PCR. In conclusion, BmAKR1-1 was screened out as candidates through the identification and analysis of the BmAKR genes in silkworm, which may regulate silkworm egg development is worthy of further investigation.

A full repertoire of Hemiptera genomes reveals a multi-step evolutionary trajectory of auto-RNA editing site in insect Adar gene.

Adenosine-to-inosine (A-to-I) RNA editing, mediated by metazoan ADAR enzymes, is a prevalent post-transcriptional modification that diversifies the proteome and promotes adaptive evolution of organisms. The Drosophila Adar gene has an auto-recoding site (termed S>G site) that forms a negative-feedback loop and stabilizes the global editing activity. However, the evolutionary trajectory of Adar S>G site in many other insects remains largely unknown, preventing us from a deeper understanding on the significance of this auto-editing mechanism. In this study, we retrieved the well-annotated genomes of 375 arthropod species including the five major insect orders (Lepidoptera, Diptera, Coleoptera, Hymenoptera and Hemiptera) and several outgroup species. We performed comparative genomic analysis on the Adar auto-recoding S>G site. We found that the ancestral state of insect S>G site was an uneditable serine codon (unSer) and that this state was largely maintained in Hymenoptera. The editable serine codon (edSer) appeared in the common ancestor of Lepidoptera, Diptera and Coleoptera and was almost fixed in the three orders. Interestingly, Hemiptera species possessed comparable numbers of unSer and edSer codons, and a few 'intermediate codons', demonstrating a multi-step evolutionary trace from unSer-to-edSer with non-synchronized mutations at three codon positions. We argue that the evolution of Adar S>G site is the best genomic evidence supporting the 'proteomic diversifying hypothesis' of RNA editing. Our work deepens our understanding on the evolutionary significance of Adar auto-recoding site which stabilizes the global editing activity and controls transcriptomic diversity.

Expression Analysis Reveals Differentially Expressed Genes in BPH and WBPH Associated with Resistance in Rice RILs Derived from a Cross between RP2068 and TN1.

BPH (brown planthopper) and WBPH (white backed planthopper) are significant rice pests that often co-occur as sympatric species and cause substantial yield loss. Despite their genetic similarities, different host-resistance genes confer resistance against these two hoppers. The defense mechanisms in rice against these pests are complex, and the molecular processes regulating their responses remain largely unknown. This study used specific recombinant inbred lines (RILs) derived from a cross between rice varieties RP2068-18-3-5 (BPH- and WBPH-resistant) and TN1 (BPH- and WBPH-susceptible) to investigate the mechanisms of interaction between these planthoppers and their rice hosts. WBPH and BPH were allowed to feed on specific RILs, and RNA-Seq was carried out on WBPH insects. Transcriptome profiling and qRT-PCR results revealed differential expression of genes involved in detoxification, digestion, transportation, cuticle formation, splicing, and RNA processing. A higher expression of sugar transporters was observed in both hoppers feeding on rice with resistance against either hopper. This is the first comparative analysis of gene expressions in these insects fed on genetically similar hosts but with differential resistance to BPH and WBPH. These results complement our earlier findings on the differential gene expression of the same RILs (BPH- or WBPH-infested) utilized in this study. Moreover, identifying insect genes and pathways responsible for countering host defense would augment our understanding of BPH and WBPH interaction with their rice hosts and enable us to develop lasting strategies to control these significant pests.

Transcriptional Readthrough Interrupts Boundary Function in Drosophila.

In higher eukaryotes, distance enhancer-promoter interactions are organized by topologically associated domains, tethering elements, and chromatin insulators/boundaries. While insulators/boundaries play a central role in chromosome organization, the mechanisms regulating their functions are largely unknown. In the studies reported here, we have taken advantage of the well-characterized Drosophila bithorax complex (BX-C) to study one potential mechanism for controlling boundary function. The regulatory domains of BX-C are flanked by boundaries, which block crosstalk with their neighboring domains and also support long-distance interactions between the regulatory domains and their target gene. As many lncRNAs have been found in BX-C, we asked whether readthrough transcription (RT) can impact boundary function. For this purpose, we took advantage of two BX-C boundary replacement platforms, Fab-7attP50 and F2attP, in which the Fab-7 and Fub boundaries, respectively, are deleted and replaced with an attP site. We introduced boundary elements, promoters, and polyadenylation signals arranged in different combinations and then assayed for boundary function. Our results show that RT can interfere with boundary activity. Since lncRNAs represent a significant fraction of Pol II transcripts in multicellular eukaryotes, it is therefore possible that RT may be a widely used mechanism to alter boundary function and regulation of gene expression.

Letrasilta, a new genus for the Striatella cernyi Volynkin species-group with description of a new species from Xizang, China, and a replacement name for the genus group name Striatella Volynkin & S.-Y. Huang, 2019 (Lepidoptera: Erebidae: Arctiinae: Lithosiini).

The name Striatochrista nom. n. is introduced as replacement for Striatella Volynkin & S.-Y. Huang, 2019. A new genus, Letrasilta S.-Y. Huang & Volynkin gen. n. is erected to include the Striatella cernyi species-group with the new species, L. ratnasambhava S.-Y. Huang, Volynkin & Yin sp. n. from Xizang, southwestern China designated as the type species. Based on the molecular phylogenetic analysis, the new genus is found to be sister to the clade (Aberrasine + ((Indiania + Idopterum) + Striatochrista nom. n.)) but is distinguished from all the relevant genera by the unique genitalia features. Letrasilta cernyi (Volynkin, 2018) comb. n. is also reported from India for the first time. Adults and genitalia of the aforementioned taxa are illustrated. A checklist of the genus Striatochrista is also provided.

A new species of planthopper from Costa Rica in the genus Herpis (Hemiptera: Derbidae) from palms in the cloud forest.

Recent survey efforts in Costa Rica have documented many new species of planthoppers, primarily in the families Derbidae and Cixiidae, on palms. Recently, a specimen was collected sweeping palms in the Los Angeles cloud forest in Costa Rica and was identified as belonging to the genus Herpis (Derbidae). It was subsequently determined to represent a previously undescribed species. Herein, the new species, Herpis circumsoros Bahder & Bartlett sp. n. is described with supplemental molecular data for the cytochrome c oxidase subunit I (COI) gene and 18S rRNA gene to support placement of the new species in the genus Herpis.

Exploring FlyBase Data Using QuickSearch.

FlyBase (www.flybase.org) is the primary online database of genetic, genomic, and functional information about Drosophila melanogaster. The long and rich history of Drosophila research, combined with recent surges in genomic-scale and high-throughput technologies, means that FlyBase now houses a huge quantity of data. Researchers need to be able to query these data rapidly and intuitively, and the QuickSearch tool has been designed to meet these needs. This tool is conveniently located on the FlyBase homepage and is organized into a series of simple tabbed interfaces that cover the major data and annotation classes within the database. This article describes the functionality of all aspects of the QuickSearch tool. With this knowledge, FlyBase users will be equipped to take full advantage of all QuickSearch features and thereby gain improved access to data relevant to their research. © 2023 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Using the "Search FlyBase" tab of QuickSearch Basic Protocol 2: Using the "Data Class" tab of QuickSearch Basic Protocol 3: Using the "References" tab of QuickSearch Basic Protocol 4: Using the "Gene Groups" tab of QuickSearch Basic Protocol 5: Using the "Pathways" tab of QuickSearch Basic Protocol 6: Using the "GO" tab of QuickSearch Basic Protocol 7: Using the "Protein Domains" tab of QuickSearch Basic Protocol 8: Using the "Expression" tab of QuickSearch Basic Protocol 9: Using the "GAL4 etc" tab of QuickSearch Basic Protocol 10: Using the "Phenotype" tab of QuickSearch Basic Protocol 11: Using the "Human Disease" tab of QuickSearch Basic Protocol 12: Using the "Homologs" tab of QuickSearch Support Protocol 1: Managing FlyBase hit lists.

The role of Dnmt1 in oocyte development.

The whitefly Bemisia tabaci is a globally important crop pest that is difficult to manage through current commercially available methods. While RNA interference (RNAi) is a promising strategy for managing this pest, effective target genes remain unclear. We suggest DNA methyltransferase 1 (Dnmt1) as a potential target gene due to its effect on fecundity in females in other taxa of insects. We investigated the role of Dnmt1 in B. tabaci using RNAi and immunohistochemistry to confirm its potential conserved function in insect reproduction, which will define its usefulness as a target gene. Using RNAi to downregulate Dnmt1 in female B. tabaci, we show that Dnmt1 indeed has a conserved role in reproduction, as knockdown interfered with oocyte development. Females in which Dnmt1 was knocked down had greatly reduced fecundity and fertility; this supports Dnmt1 as a suitable target gene for RNAi-mediated pest management of B. tabaci.

Evaluation of suitable reference genes for expression analysis using quantitative real-time polymerase chain reaction in the parasitoid Exorista sorbillans (Diptera: Tachinidae).

The parasitoid Exorista sorbillans (Diptera: Tachinidae) is a larval endoparasitoid of the silkworm Bombyx mori, causing severe damage to silkworm cocoon industry. It is also an important natural enemy resource of insect pests in agriculture and forestry. Despite their roles in biocontrol and pest status on sericulture, there has been limited research on the functional studies of dipteran parasitoids. Quantitative real-time polymerase chain reaction (qRT-PCR) is the most commonly used to address gene functions. Using qRT-PCR, stably expressed reference genes under different experimental conditions are required to normalize the expression of target genes. However, no information regarding suitable qRT-PCR reference genes in dipteran parasitoids has been reported. In this study, we evaluate the expression stability of nine commonly used reference genes in insects including eukaryotic translation elongation factor 1δ (eEF1δ), elongation factor 2, 18S ribosomal RNA (18S rRNA), tubulin 3, actin87, ribosomal protein 49 (RP49), ribosomal protein S15, glyceraldehyde-3-phosphate dehydrogenase, and TATA-box binding protein (TBP) in E. sorbillans under different treatments, including tissues, developmental stages, genders, feeding density and pesticide stress, using ∆Ct , BestKeeper, geNorm, Normfinder and RefFinder, respectively. The results showed that the genes RP49, eEF1δ and 18S rRNA were recommended as the most suitable reference genes in E. sorbillans across all experimental conditions. This finding provides the necessary foundation for future functional studies in E. sorbillans and its effective use in both sericulture and pest control.

The Effect of Developmental Pleiotropy on the Evolution of Insect Immune Genes.

The pressure to survive ever-changing pathogen exposure explains the frequent observation that immune genes are among the fastest evolving in the genomes of many taxa, but an intriguing proportion of immune genes also appear to be under purifying selection. Though variance in evolutionary signatures of immune genes is often attributed to differences in gene-specific interactions with microbes, this explanation neglects the possibility that immune genes participate in other biological processes that could pleiotropically constrain adaptive selection. In this study, we analyzed available transcriptomic and genomic data from Drosophila melanogaster and related species to test the hypothesis that there is substantial pleiotropic overlap in the developmental and immunological functions of genes involved in immune signaling and that pleiotropy would be associated with stronger signatures of evolutionary constraint. Our results suggest that pleiotropic immune genes do evolve more slowly than those having no known developmental functions and that signatures of constraint are particularly strong for pleiotropic immune genes that are broadly expressed across life stages. These results support the general yet untested hypothesis that pleiotropy can constrain immune system evolution, raising new fundamental questions about the benefits of maintaining pleiotropy in systems that need to rapidly adapt to changing pathogen pressures.