Abstract There is disagreement on whether secondary endosymbionts are found in the major cereal pest aphid, Rhopalosiphum padi . Some papers report a diversity of secondary bacterial endosymbionts while others have failed to find evidence of these bacteria in this species. Here we revisit this issue by summarizing the relevant literature and through additional sampling of the species in Australia, China and Denmark using a combination of molecular approaches. We find a general absence of secondary endosymbionts beyond the obligate endosymbiont Hamiltonella defensa in R. padi . While the inconsistency in survey results may reflect rapid changes in endosymbiont turnover in populations and/or the impact of ecological factors such as host plant type on endosymbiont diversity, we are concerned that technical issues may be at least partly responsible for inconsistencies in the literature. This leads us to emphasize the importance of multiple sources of evidence required to establish and characterize endosymbiont infections, including PCR and qPCR assays, DNA Sanger sequencing and 16SrRNA gene metabarcoding. We note that several major aphid pests show a low incidence of secondary endosymbionts which raises issues about the importance of these endosymbionts in aphids that constitute pests, even though endosymbionts can in some cases increase host fitness and therefore pest impact.

Insects can survive in nutrient-poor environments owing to nutritional symbionts that produce vitamins and essential amino acids (EAAs). Nonetheless, how symbionts actively benefit from this nutritional symbiosis remains incompletely understood. Horizontally transferred genes (HTGs) expressed in bacteriocytes can function autonomously or cooperatively with symbionts to biosynthesize EAAs or B vitamins. We previously demonstrated that the horizontally transferred panBC and the symbiont Portiera cooperatively synthesize vitamin B5 (pantothenate), thereby enhancing whitefly fecundity. Beyond supporting host reproduction, this nutritional symbiosis also confers a fitness advantage on the symbionts. We further showed that induction of autophagy reduces symbiont abundance in bacteriocytes, whereas inhibition of autophagy increases it. Here, we found that silencing panBC reduced Portiera titer, impaired whitefly oogenesis, and disrupted vitellogenin (Vg) localization in ovarioles and bacteriocytes by modulating juvenile hormone biosynthesis. Pantothenate supplementation restored Vg localization in panBC RNAi whiteflies. Furthermore, silencing either Vg or panBC induced autophagy in bacteriocytes, and rapamycin-induced autophagy decreased symbiont titers. Taken together, our findings demonstrate that pantothenate, synthesized cooperatively by the horizontally transferred panBC and Portiera, regulates Vg localization in whiteflies and that Vg, in turn, protects symbionts from autophagic degradation. Our study suggests that horizontally transferred genes and symbionts jointly contribute to an important role of Vg in maintaining and shaping the evolution of insect-symbiont interactions. This study advances our understanding of how HTGs contribute to the persistence of nutritional symbiosis.

BACKGROUND:Symbionts influence the biological and ecological traits of host insects. Regulating the insect-microbe symbiosis represents new strategies for pest control. We previously demonstrated that autophagy induction regulates the abundance of bacteriocyte symbionts in the whitefly Bemisia tabaci MEAM1. RESULTS:This study further investigated whether autophagy induction via silencing the Target of Rapamycin (TOR) pathway genes (LST8 and TOR) using the plant-mediated gene silencing technology can repress the symbiont abundance and fitness of another invasive whitefly B. tabaci MED. We found that whitefly LST8 and TOR genes can be silenced by virus induced gene silencing approach. LST8 and TOR gene silencing significantly up-regulated the expression of autophagy marker gene Atg8 and led to reduction in the abundance of the symbionts Portiera, Hamiltonella, and Rickettsia in whiteflies. This reduction in symbiont titers led to increased mortality and decreased fecundity in whiteflies. CONCLUSION:These findings underscore the potential of manipulating autophagy to disrupt symbiotic abundance as a novel and environmentally friendly strategy for pest management. Our study also suggests that disruption of intracellular symbiosis via insect immunity modulation is feasible for the management of sap-sucking insect pests. © 2026 Society of Chemical Industry.

Defensive symbioses in which beneficial microbes protect hosts from natural enemies are ubiquitous across animals and plants, but the underlying mechanisms remain poorly understood. Field surveys and laboratory assays revealed that infection of the invasive whitefly Bemisia tabaci by the bacterial symbiont Rickettsia and plant begomovirus were positively correlated with each other but each negatively correlated with a parasitic fungal infection (Beauveria bassiana) in the host. We show that begomovirus conferred whitefly's resistance to the parasitic fungus by triggering the expression of chitin synthesis pathway genes in whiteflies, reinforcing the cuticle by promoting chitin production. The facultative symbiont Rickettsia facilitated cuticle formation and thereby induced physical defense against entomopathogenic fungus via metabolic cooperation with the obligate symbiont Portiera for the synthesis of phenylalanine and tyrosine in whiteflies, which is used to generate cuticular proteins and pigments. Mutation of chitinase and protease genes in B. bassiana impaired fungal infection of whiteflies. Inhibiting whitefly cuticle formation by repressing chitin and phenylalanine synthesis facilitated fungal infection. Thus, begomovirus and Rickettsia have convergent effects on cuticle defense in whiteflies by impacting distinct molecular pathways. Such defensive symbioses apparently contribute to B. tabaci fitness in the field and our findings reveal that interactions among the host, beneficial microbes, and pathogens have important implications for insect ecology and evolution. This study suggests avenues for pest management by leveraging defensive microbes and targeting the host cuticle.

Tomato mottle mosaic virus (ToMMV) is a major threat to cultivating tomatoes and other solanaceous plants. Here, an infectious clone of the ToMMV Huludao isolate was constructed, and ToMMV infection significantly reduces soluble sugar, soluble phenolic, and vitamin C contents, while increases titratable acid content in Micro-Tom fruits, thus altering their flavor profile and quality. Integrated transcriptomic and metabolomic analysis indicate that ToMMV infection induced 2090 differentially expressed genes and 709 differentially accumulated metabolites in Micro-Tom fruits. Then, functional analysis using gene silencing validated that bifunctional 3-dehydroquinate dehydratase/shikimate dehydrogenase and glyceraldehyde-3-phosphate dehydrogenase induced by ToMMV in the amino acid biosynthesis pathway play critical roles in tomato fruit quality, while 4-coumarate-CoA ligase, phenylalanine ammonia-lyase and scopoletin glucosyltransferase in the phenylpropanoid biosynthesis pathway were required for host resistance. Our findings elucidate molecular mechanisms of ToMMV-induced fruit quality alteration and highlight metabolic targets for enhanced viral resistance in tomatoes.

Insects have specialized host cells, namely bacteriocytes, to house intracellular symbionts. However, knowledge of the mechanisms underlying regulation of bacteriocyte development and associated symbiont abundance during insect embryogenesis is scarce. One bacteriocyte translocates and divides into two cells, and abundance of bacteriocyte symbionts fluctuates periodically during embryogenesis of whitefly Bemisia tabaci MEAM1. We find that the Akirin gene is highly expressed in bacteriocytes, and its expression level is inversely correlated to symbiont titers during whitefly embryogenesis. Silencing Akirin inhibits the translocation and division of the bacteriocyte in embryos but increases bacteriocyte size and symbiont titers. Akirin controls titers of bacteriocyte symbionts by positively affecting the expression of the antimicrobial peptide gene defensin. Thus, Akirin has a dual function in regulating cell development and symbiont abundance of bacteriocytes in whitefly embryos. This study opens another direction to study mechanisms underlying development regulation of novel cells like bacteriocytes.

BACKGROUND:Maternally inherited symbionts can impact the reproduction of their host insects in various ways. The ovary is critical for the successful reproduction of female insects. Such symbionts have strong ovary tropism. Intracellular symbionts depend on host cells for replication and transmission. However, the cellular mechanisms by which symbionts impact insect reproduction through affecting ovary development have seldom been investigated. Our previous work has shown that the facultative symbiont Rickettsia can be vertically transmitted through eggs in the whitefly Bemisia tabaci and Rickettsia increases female fecundity. This study is aimed to explore the cellular mechanisms of Rickettsia symbionts affecting the whitefly fecundity. RESULTS:We found that Rickettsia symbionts are highly concentrated in the tropharium of whitefly ovarioles. We demonstrated that Rickettsia increases whitefly fecundity by promoting ovary development. Moreover, Rickettsia enhances the expression of cell division genes (Cyclin B1 and CDK1) and germ cell mitosis. Furthermore, Cyclin B1 and CDK1 gene silencing or CDK1 inhibitor treatment reduced the germ cell mitosis, delayed ovary development and decreased whitefly fecundity. CONCLUSION:Overall, we revealed that Rickettsia promotes ovary development by regulating germ cell mitosis, which enhances whitefly fecundity. These findings suggest that regulating the host cell cycle by the symbiont is important for the maintenance of the intracellular symbiosis. This study provides new insights into the cellular mechanism of symbionts regulating host reproduction. Our study also provides excellent genetic targets for insect control. © 2025 Society of Chemical Industry.

Weak light threatens crop yield by impairing plant photosynthesis and growth. How to improve crop growth under such circumstances is extremely important for the agriculture and forestry. Photosynthetic bacteria can utilize bacteriochlorophyll to photosynthesize in weak light and anaerobic environments where plants cannot survive. Whether photosynthetic bacteria can be used to improve photosynthesis of plants under weak light environments has not been reported. Here, we found that foliar spraying of photosynthetic Rhodopseudomonas palustris strain CGA009 delayed leaf senescence and enhanced tomato photosynthesis under weak light conditions. Bacteria treatment maintained chlorophyll level by promoting the degradation of the negative regulator SlPIF4, which thereby relieved the repression of cytokinin biosynthesis genes SlIPT6/SlLOG8. Silencing of SlIPT6 and SlLOG8 made tomato plants insensitive to R. palustris treatment under weak light conditions, leading to a decrease in the synthesis of the active cytokinin N6-Isopentenyladenine (iP) and cis-Zeatin (cZ). Our findings demonstrated that R. palustris can rescue the photosynthetic capacity of tomatoes under weak light conditions through transcription regulation. Thus, this study provides an avenue to enhance crop yield under weak light stress by plant photosynthesis improvement mediated via photosynthetic bacteria.

Bacteriocytes are specialized insect cells adapted to harbor symbionts. However, their low number in individual whiteflies makes obtaining enough for transcriptome sequencing challenging. Here, we present a protocol for the isolation of whitefly bacteriocytes. We describe steps for preparing the single bacteriocyte sample, cDNA amplification library construction, sequencing, and data analysis. Our protocol offers convenience and efficiency for conducting single-cell sequencing for bacteriocytes and has the potential to be applied to other insect cells. For complete details on the use and execution of this protocol, please refer to Li et al.1.

With the continuous growth of global agricultural production, pest control has become a critical factor in ensuring crop health and increasing agricultural output. In view of the safety of food and ecology, the development of more environmentally friendly and sustainable approaches for pest management is desirable. All insects are colonized by microorganisms on the insect cuticle or in the body. These resident microorganisms can promote insect fitness, impact the transmission of plant pathogens, or protect insects against natural enemies and adverse environments. Thus, insect‒microbe symbiosis-based strategies provide a new avenue for the management of insect pests and their transmitted pathogens. This review summarizes developments in the field of pest control approaches based on insect‒microbe symbiosis and proposes future directions. First, we introduce insect symbiotic microorganisms and their functions. This review discusses the application of insect-microbe symbiosis-based pest control strategies, including the application of native or engineered symbionts, the utilization of bioactive substances produced by symbiotic microorganisms, and the development of an insect symbiosis disruption strategy. Despite the great potential of this novel pest-control strategy, many challenges remain, such as the stability of symbiotic bacteria, their environmental adaptability, and their impact on non-target organisms. Finally, the review concludes by suggesting future directions, including improving the targeting specificity of symbiotic bacteria, enhancing their environmental adaptability, and developing integrated pest management strategies that combine this means with others to achieve more sustainable and effective pest control.

Although it is widely recognized that nutritional symbionts can manipulate host reproduction, the underlying molecular and cellular mechanisms are largely unclear. The facultative symbiont Hamiltonella in bacteriocyte induces female-biased sex ratio of whiteflies. Here, we demonstrate that a maternal gene tudor (tud) and its encoded protein have lower expression levels in ovaries of Hamiltonella-cured whiteflies. Tud family proteins can interlink the various stages of biosynthesis of PIWI-interacting RNA (piRNA), a class of small noncoding RNAs. We find that Hamiltonella affects the abundance of a piRNA through the maternal gene tud, thereby regulating the expression of the vacuolar (H+)-ATPase H subunit (VATPH), which is the switch of activity of the vacuolar (H+)-ATPase that plays a crucial role in maintaining the homeostasis of intracellular energy and supporting mitochondrial respiration. This regulation adjusts the ATP level in ovaries of whiteflies. The ATP level shapes the F-actin pattern in ovaries and eggs of whiteflies, ultimately manipulating whitefly fertilization. Silencing tud inhibited whitefly fertilization by impairing ATP levels and F-actin patterns in ovaries and eggs. This study reveals that symbiont and maternal protein associations can regulate host fertilization by piRNA biosynthesis.

The metabolic cooperation for the phenylalanine synthesis between the host and its obligate symbiont is widespread in hemipteran insects. However, the mechanisms underlying phenylalanine synthesis and its role in hemipteran insects are largely unknown. Our previous study indicates that the whitefly Bemisia tabaci glutamate–oxaloacetate transaminase gene GOT2 compensates for tyrB missing from Portiera. Here, we found that the whitefly GOT2 and Portiera can cooperate for the synthesis of phenylalanine mainly by silencing GOT2. We further revealed that the phenylalanine synthesized by whitefly–Portiera symbiosis promotes cuticle formation on adult whiteflies. Then, we demonstrated that repression of phenylalanine synthesis by silencing whitefly GOT2 does not significantly increase the whitefly mortality under high temperature and low humidity conditions, but it enhances the whitefly mortality when whiteflies were infected with the entomopathogenic fungi Beauveria bassiana. Our results provide experimental evidence on how symbiosis contributes to adult whitefly cuticle formation, revealing parallel histories of the phenylalanine synthesized by the host and its obligate symbiont facilitated cuticle formation in insects housing the bacteriocyte symbionts. This study indicates that the phenylalanine synthesized by insect–bacteria symbiosis may confer the insect adaptation to entomopathogenic fungi. Our findings will also help us to develop an insect symbiosis disruption strategy for pest control.

Some endosymbionts manipulate host reproduction to enhance transmission, thereby influencing host sex determination. Among reproductive manipulations, parthenogenesis induction represents a highly efficient strategy. This phenomenon is primarily mediated by symbiotic bacteria such as Wolbachia, Cardinium, and Rickettsia. Unlike Wolbachia mechanisms are well-documented, Rickettsia-induced parthenogenesis remains poorly characterized. In this study, we demonstrate for the first time that thelytoky (unfertilized eggs develop into diploid females) in an Eupelmid wasp, Anastatus gansuensis, is induced by Rickettsia, as confirmed through lifetime fecundity analysis, antibiotic treatment, and molecular testing. Gene sequencing and phylogenetic analysis identified a single reproductive symbiont, Rickettsia, belonging to a new species in the R. bellii clade. Fluorescence in situ hybridization (FISH) and qPCR revealed high Rickettsia titers primarily localized in the ovaries, with vertical transmission to offspring. Antibiotic treatment significantly reduced Rickettsia titers, leading to increased male offspring. This study demonstrates that Rickettsia, vertically transmitted via the ovaries, plays a pivotal role in inducing parthenogenesis in its host. These findings establish a foundation for investigating sex determination mechanisms in Anastatus.

Bacteriocytes are host cells specialized to harbor symbionts in certain insect taxa. The adaptation, development, and evolution of bacteriocytes underlie insect symbiosis maintenance. Bacteriocytes carry enriched host genes of insect and bacterial origin whose transcription can be regulated by microRNAs, which are involved in host-symbiont metabolic interactions. Recognition proteins of peptidoglycan, the bacterial cell wall component, and autophagy regulate symbiont abundance in bacteriocytes. Horizontally transferred genes expressed in bacteriocytes influence the metabolism of symbiont peptidoglycan, which may affect the bacteriocyte immune response against symbionts. Bacteriocytes release or transport symbionts into ovaries for symbiont vertical transmission. Bacteriocyte development and death, regulated by transcriptional factors, are variable in different insect species. The evolutionary origin of insect bacteriocytes remains unclear. Future research should elucidate bacteriocyte cell biology, the molecular interplay between bacteriocyte metabolic and immune functions, the genetic basis of bacteriocyte origin, and the coordination between bacteriocyte function and host biology in diverse symbioses.

Heritable symbionts are common among animals in nature, but the molecular mechanisms underpinning symbiont invasions of host populations have been elusive. In this study, we demonstrate the spread ofRickettsiain an invasive agricultural pest, the whiteflyBemisia tabaciMediterranean (MED), across northeastern China from 2018 to 2023. Here, we show that the beneficial symbiontRickettsiaspreads by manipulating host hormone signals. Our analyses suggest thatRickettsiahave been horizontally acquired byB. tabaciMED from another invasive whiteflyB. tabaciMiddle East-Asia Minor 1 during periods of coexistence.Rickettsiais transmitted maternally and horizontally from femaleB. tabaciMED individuals.Rickettsiainfection enhances fecundity and results in female bias among whiteflies. Our findings reveal thatRickettsiainfection stimulates juvenile hormone (JH) synthesis, in turn enhancing fecundity, copulation events, and the female ratio of the offspring. Consequently,Rickettsiainfection results in increased whitefly fecundity and female bias by modulating the JH pathway. More female progeny facilitates the transmission ofRickettsia. This study illustrates that the spread ofRickettsiaamong invasive whiteflies in northeastern China is propelled by host hormone regulation. Such symbiont invasions lead to rapid physiological and molecular evolution in the host, influencing the biology and ecology of an invasive species.

Host reproduction can be manipulated by bacterial symbionts in various ways. Parthenogenesis induction is the most effective type of reproduction manipulation by symbionts for their transmission. Insect sex is determined by regulation of doublesex (dsx) splicing through transformer2 (tra2) and transformer (tra) interaction. Although parthenogenesis induction by symbionts has been studied since the 1970s, its underlying molecular mechanism is unknown. Here we identify a Wolbachia parthenogenesis-induction feminization factor gene (piff) that targets sex-determining genes and causes female-producing parthenogenesis in the haplodiploid parasitoid Encarsia formosa. We found that Wolbachia elimination repressed expression of female-specific dsx and enhanced expression of male-specific dsx, which led to the production of wasp haploid male offspring. Furthermore, we found that E. formosa tra is truncated and non-functional, and Wolbachia has a functional tra homolog, termed piff, with an insect origin. Wolbachia PIFF can colocalize and interact with wasp TRA2. Moreover, Wolbachia piff has coordinated expression with tra2 and dsx of E. formosa. Our results demonstrate the bacterial symbiont Wolbachia has acquired an insect gene to manipulate the host sex determination cascade and induce parthenogenesis in wasps. This study reveals insect-to-bacteria horizontal gene transfer drives the evolution of animal sex determination systems, elucidating a striking mechanism of insect-microbe symbiosis.

Nutritional symbionts influence host reproduction, but the underlying molecular mechanisms are largely unclear. We previously found that the bacteriocyte symbiont Hamiltonella impacts the sex ratio of the whitefly Bemisia tabaci. Hamiltonella synthesizes folate by cooperation with the whitefly. Folate deficiency by Hamiltonella elimination or whitefly gene silencing distorted whitefly sex ratio, and folate supplementation restored the sex ratio. Hamiltonella deficiency or gene silencing altered histone H3 lysine 9 trimethylation (H3K9me3) level, which was restored by folate supplementation. Genome-wide chromatin immunoprecipitation-seq analysis of H3K9me3 indicated mitochondrial dysfunction in symbiont-deficient whiteflies. Hamiltonella deficiency compromised mitochondrial quality of whitefly ovaries. Repressing ovary mitochondrial function led to distorted whitefly sex ratio. These findings indicate that the symbiont-derived folate regulates host histone methylation modifications, which thereby impacts ovary mitochondrial function, and finally determines host sex ratio. Our study suggests that a nutritional symbiont can regulate animal reproduction in a way that differs from reproductive manipulators.

近5年来,我国在害虫变态发育与生殖调控、害虫滞育调控、害虫迁飞、害虫与共生微生物互作、害虫对杀虫剂的抗性、害虫与寄主植物的化学通讯、害虫对植物抗虫性的适应、害虫对作物种植结构调整的响应、害虫对全球气候变化的响应等农业害虫发生新规律新机制解析方面取得了系列重要进展,同时推进了抗虫作物、RNA农药、行为调控和生态调控等害虫防控新技术与新产品的研发;提出迁飞性草地贪夜蛾分区治理、多食性盲蝽区域防控、地下害虫韭蛆绿色防控和抗性麦蚜精准化学防控等害虫绿色防控新模式新体系.根据国内外农业害虫综合防治科技发展趋势和中国农业高质量发展现实需求,我国需进一步重视农业昆虫交叉学科前沿和新兴技术领域,以产业需求为导向,强化害虫防控基础理论创新,创制智能监测预警和绿色防控新技术、新产品,创新集成区域绿色防控和跨区协同治理技术体系,为保障国家粮食安全、助力乡村全面振兴提供强有力的植保科技支撑.

Hymenoptera is an order accounting for a large proportion of species in Insecta, among which Chalcidoidea contains many parasitoid species of biocontrol significance. Currently, some species genomes in Chalcidoidea have been assembled, but the chromosome-level genomes of Aphelinidae are not yet available. Using Illumina, PacBio HiFi and Hi-C technologies, we assembled a genome assembly of Eretmocerus hayati (Aphelinidae, Hymenoptera), a worldwide biocontrol agent of whiteflies, at the chromosome level. The assembled genome size is 692.1 Mb with a contig N50 of 7.96 Mb. After Hi-C scaffolding, the contigs was assembled onto four chromosomes with a mapping rate of > 98%. The scaffold N50 length is 192.5 Mb, and Benchmarking Universal Single-Copy Orthologues (BUSCO) value is 95.9%. The genome contains 370.8 Mb repeat sequences and total of 24471 protein coding genes. P450 gene families were identified and analyzed. In conclusion, our chromosome-level genome assembly provides valuable support for future research on the evolution of parasitoid wasps and the interaction between hosts and parasitoid wasps.

Intracellular heritable symbionts have been incorporated into insect reproductive and developmental biology by various mechanisms. All Bemisia tabaci species harbor the obligate symbiont Portiera in specialized insect cells called bacteriocytes. We report that the whitefly juvenile hormone and Portiera determined vitellogenin (Vg) localization in bacteriocytes of whiteflies.