Retention of an Endosymbiont for the Production of a Single Molecule.

Sap-feeding insects often maintain two or more nutritional endosymbionts that act in concert to produce compounds essential for insect survival. Many mealybugs have endosymbionts in a nested configuration: one or two bacterial species reside within the cytoplasm of another bacterium, and together, these bacteria have genomes that encode interdependent sets of genes needed to produce key nutritional molecules. Here, we show that the mealybug Pseudococcus viburni has three endosymbionts, one of which contributes only two unique genes that produce the host nutrition-related molecule chorismate. All three bacterial endosymbionts have tiny genomes, suggesting that they have been coevolving inside their insect host for millions of years.

Specifically targeting antimicrobial peptides for inhibition of Candidatus Liberibacter asiaticus.

AIMS: Huanglongbing (citrus greening) is a plant disease putatively caused by the unculturable Gram-negative bacterium Candidatus Liberibacter asiaticus (CLas), and it has caused severe damage to citrus plantations worldwide. There are no definitive treatments for this disease, and conventional disease control techniques have shown limited efficacy. This work presents an in silico evaluation of using specifically targeting anti-microbial peptides (STAMPs) consisting of a targeting segment and an antimicrobial segment to inhibit citrus greening by inhibiting the BamA protein of CLas, which is an outer membrane protein crucial for bacterial viability. METHODS AND RESULTS: Initially, a set of peptides with a high affinity toward BamA protein were screened and evaluated via molecular docking and molecular dynamics simulations and were verified in vitro via bio-layer interferometry (BLI). In silico studies and BLI experiments indicated that two peptides, HASP2 and HASP3, showed stable binding to BamA. Protein structures for STAMPs were created by fusing known anti-microbial peptides (AMPs) with the selected short peptides. The binding of STAMPs to BamA was assessed using molecular docking and binding energy calculations. The attachment of high-affinity short peptides significantly reduced the free energy of binding for AMPs, suggesting that it would make it easier for the STAMPs to bind to BamA. Efficacy testing in vitro using a closely related CLas surrogate bacterium showed that STAMPs had greater inhibitory activity than AMP alone. CONCLUSIONS: In silico and in vitro results indicate that the STAMPs can inhibit CLas surrogate Rhizobium grahamii more effectively compared to AMPs, suggesting that STAMPs can achieve better inhibition of CLas, potentially via enhancing the site specificity of AMPs.

Endosymbiont Tremblaya phenacola influences the reproduction of cotton mealybugs by regulating the mechanistic target of rapamycin pathway.

The intricate evolutionary dynamics of endosymbiotic relationships result in unique characteristics among the genomes of symbionts, which profoundly influence host insect phenotypes. Here, we investigated an endosymbiotic system in Phenacoccus solenopsis, a notorious pest of the subfamily Phenacoccinae. The endosymbiont, "Candidatus Tremblaya phenacola" (T. phenacola PSOL), persisted throughout the complete life cycle of female hosts and was more active during oviposition, whereas there was a significant decline in abundance after pupation in males. Genome sequencing yielded an endosymbiont genome of 221.1 kb in size, comprising seven contigs and originating from a chimeric arrangement between betaproteobacteria and gammaproteobacteria. A comprehensive analysis of amino acid metabolic pathways demonstrated complementarity between the host and endosymbiont metabolism. Elimination of T. phenacola PSOL through antibiotic treatment significantly decreased P. solenopsis fecundity. Weighted gene coexpression network analysis demonstrated a correlation between genes associated with essential amino acid synthesis and those associated with host meiosis and oocyte maturation. Moreover, altering endosymbiont abundance activated the host mechanistic target of rapamycin pathway, suggesting that changes in the amino acid abundance affected the host reproductive capabilities via this signal pathway. Taken together, these findings demonstrate a mechanism by which the endosymbiont T. phenacola PSOL contributed to high fecundity in P. solenopsis and provide new insights into nutritional compensation and coevolution of the endosymbiotic system.

Rickettsia transmission from whitefly to plants benefits herbivore insects but is detrimental to fungal and viral pathogens.

Bacterial endosymbionts play important roles in the life histories of herbivorous insects by impacting their development, survival, reproduction, and stress tolerance. How endosymbionts may affect the interactions between plants and insect herbivores is still largely unclear. Here, we show that endosymbiotic Rickettsia belli can provide mutual benefits also outside of their hosts when the sap-sucking whitefly Bemisia tabaci transmits them to plants. This transmission facilitates the spread of Rickettsia but is shown to also enhance the performance of the whitefly and co-infesting caterpillars. In contrast, Rickettsia infection enhanced plant resistance to several pathogens. Inside the plants, Rickettsia triggers the expression of salicylic acid-related genes and the two pathogen-resistance genes TGA 2.1 and VRP, whereas they repressed genes of the jasmonic acid pathway. Performance experiments using wild type and mutant tomato plants confirmed that Rickettsia enhances the plants' suitability for insect herbivores but makes them more resistant to fungal and viral pathogens. Our results imply that endosymbiotic Rickettsia of phloem-feeding insects affects plant defenses in a manner that facilitates their spread and transmission. This novel insight into how insects can exploit endosymbionts to manipulate plant defenses also opens possibilities to interfere with their ability to do so as a crop protection strategy. IMPORTANCE: Most insects are associated with symbiotic bacteria in nature. These symbionts play important roles in the life histories of herbivorous insects by impacting their development, survival, reproduction as well as stress tolerance. Rickettsia is one important symbiont to the agricultural pest whitefly Bemisia tabaci. Here, for the first time, we revealed that the persistence of Rickettsia symbionts in tomato leaves significantly changed the defense pattern of tomato plants. These changes benefit both sap-feeding and leaf-chewing herbivore insects, such as increasing the fecundity of whitefly adults, enhancing the growth and development of the noctuid Spodoptera litura, but reducing the pathogenicity of Verticillium fungi and TYLCV virus to tomato plants distinctively. Our study unraveled a new horizon for the multiple interaction theories among plant-insect-bacterial symbionts.

Two horizontally acquired bacterial genes steer the exceptionally efficient and flexible nitrogenous waste cycling in whiteflies.

Nitrogen is an essential element for all life on earth. Nitrogen metabolism, including excretion, is essential for growth, development, and survival of plants and animals alike. Several nitrogen metabolic processes have been described, but the underlying molecular mechanisms are unclear. Here, we reveal a unique process of nitrogen metabolism in the whitefly Bemisia tabaci, a global pest. We show that it has acquired two bacterial uricolytic enzyme genes, B. tabaci urea carboxylase (BtUCA) and B. tabaci allophanate hydrolase (BtAtzF), through horizontal gene transfer. These genes operate in conjunction to not only coordinate an efficient way of metabolizing nitrogenous waste but also control B. tabaci's exceptionally flexible nitrogen recycling capacity. Its efficient nitrogen processing explains how this important pest can feed on a vast spectrum of plants. This finding provides insight into how the hijacking of microbial genes has allowed whiteflies to develop a highly economic and stable nitrogen metabolism network and offers clues for pest management strategies.

Morphological and phylogenetic resolution of Conoideocrella luteorostrata (Hypocreales: Clavicipitaceae), a potential biocontrol fungus for Fiorinia externa in United States Christmas tree production areas.

The entomopathogenic fungus Conoideocrella luteorostrata has recently been implicated in natural epizootics among exotic elongate hemlock scale (EHS) insects in Christmas tree farms in the eastern United States. Since 1913, C. luteorostrata has been reported from various plant feeding Hemiptera in the southeastern United States, but comprehensive morphological and phylogenetic studies of U.S. populations are lacking. The recovery of multiple strains of C. luteorostrata from mycosed EHS in North Carolina provided an opportunity to conduct pathogenicity assays and morphological and phylogenetic studies to investigate genus- and species-level boundaries among the Clavicipitaceae. Pathogenicity assays confirmed that C. luteorostrata causes mortality of EHS crawlers, an essential first step in developing this fungus as a biocontrol. Morphological studies revealed that conidia aligned with previous measurements of the Paecilomyces-like asexual state of C. luteorostrata, with conidiophore morphology consistent with historical observations. Additionally, a Hirsutella-like synanamorph was observed in select C. luteorostrata strains. In both a four-locus, 54-taxon Clavicipitaceae-wide phylogenetic analysis including D1-D2 domains of the nuclear 28S rRNA region (28S), elongation factor 1 alpha (EF1-α), DNA-directed RNA polymerase II subunit 1 (RPB1), and DNA-directed RNA polymerase II subunit 2 (RPB2) and a two-locus, 38-taxon (28S and EF1-α) phylogenetic analysis, all three Conoideocrella species were resolved as strongly supported monophyletic lineages across all loci and both methods (maximum likelihood and Bayesian inference) of phylogenetic inference except for 28S for C. tenuis. Despite the strong support for individual Conoideocrella species, none of the analyses supported the monophyly of Conoideocrella with the inclusion of Dussiella. Due to the paucity of RPB1 and RPB2 sequence data, EF1-α provided superior delimitation of intraspecies groupings for Conoideocrella and should be used in future studies. Further development of C. luteorostrata as a biocontrol against EHS will require additional surveys across diverse Hemiptera and expanded pathogenicity testing to clarify host range and efficacy of this fungus.

Insect Bacteriocytes: Adaptation, Development, and Evolution.

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.

The Hidden Secrets of Psylloidea: Biology, Behavior, Symbionts, and Ecology.

Psyllids constitute a diverse group of sap-feeding Sternorrhyncha that were relatively obscure until it was discovered that a handful of species transmit bacterial plant pathogens. Yet the superfamily Psylloidea is much richer than the sum of its crop-associated vectors, with over 4,000 described species exhibiting diverse life histories and host exploitation strategies. A growing body of research is uncovering fascinating insights into psyllid evolution, biology, behavior, and species interactions. This work has revealed commonalities and differences with better-studied Sternorrhyncha, as well as unique evolutionary patterns of lineage divergence and host use. We are also learning how psyllid evolution and foraging ecology underlie life history traits and the roles of psyllids in communities. At finer scales, we are untangling the web of symbionts across the psyllid family tree, linking symbiont and psyllid lineages, and revealing mechanisms underlying reciprocal exchange between symbiont and host. In this review, we synthesize and summarize key advances within these areas with a focus on free-living (nongalling) Psylloidea.

Fusarium species associated with citrus blackfly (Aleurocanthus woglumi) from an agroecological polyculture in Brazil, including an augmented description of F. volatile.

The objectives of this study were to report Fusarium species associated with Aleurocanthus woglumi (Hemiptera: Aleyrodidae) collected from citrus leaves from an agroecological polyculture in Brazil, assess sexual reproductive mode of the species with unknown sexual stages, and provide an augmented description of F. volatile, for which we discovered a sexual stage. Nineteen Fusarium isolates were recovered from A. woglumi. These fungi belong to three species complexes, i.e., the F. chlamydosporum species complex (FCSC), the F. fujikuroi species complex (FFSC), and the F. incarnatum-equiseti species complex (FIESC). Based on multilocus phylogenetic analyses, the species were identified as F. annulatum, F. chlamydosporum, F. pernambucanum, F. sulawesiense, F. verticillioides, and F. volatile. Our results suggest that three species whose sexual stages are unknown (F. chlamydosporum, F. sulawesiense, and F. volatile) are also heterothallic. Intraspecific crosses of F. sulawesiense and F. volatile produced protoperithecia, whereas 66.7% of F. volatile crosses produced fertile perithecia. We provide an augmented description of the latter species to include characteristics of its sexual morph and those observed in the asexual morph that had not yet been described for the species. This study highlights the potential of researching insect-associated fungi to increase knowledge about the diversity, taxonomy, and versatility of Fusarium in ecosystems.

DC-electrical penetration graph waveforms for Dalbulus maidis (Hemiptera: Cicadellidae) and the effects of entomopathogenic fungi on its probing behavior.

The corn leafhopper Dalbulus maidis is an important transmitter of viruses and bacteria to maize plants. Data on the stylet probing and ingestion behavior of D. maidis, gathered using the DC-electrical penetration graph (DC-EPG) technique, are limited. The increasing prevalence of this pest and the diseases that it transmits in maize crops heighten the importance of studying how control tools affect the probing behavior of these insects, to reduce or prevent the chances of pathogen transmission and the damage from feeding. Our study recorded stylet activities of D. maidis, using a DC-EPG system and compared the appearances of waveforms with those from published AC and AC-DC EPG studies. All types of systems produced similar waveform appearances; therefore, we used the waveform nomenclature previously published. We also determined the effects of the entomopathogenic fungus Cordyceps javanica on the probing behavior of D. maidis at different time points after the fungus was applied by spraying. Forty-eight hours after the insects were sprayed, the effects were pronounced, with significant disruption of the stylet activities in phloem and non-phloem phases. Our study indicated that this commercial microbiological product, with the active ingredient C. javanica, can alter the probing behavior of D. maidis and may be helpful in management of the vector.

Diaphorin, a polyketide produced by a bacterial endosymbiont of the Asian citrus psyllid, adversely affects the in vitro gene expression with ribosomes from Escherichia coli and Bacillus subtilis.

Diaphorin is a polyketide produced by "Candidatus Profftella armatura" (Gammaproteobacteria), an obligate mutualist of an important agricultural pest, the Asian citrus psyllid Diaphorina citri (Hemiptera). Our previous study demonstrated that diaphorin, at physiological concentrations in D. citri, inhibits the growth and cell division of Bacillus subtilis (Firmicutes) but promotes the growth and metabolic activity of Escherichia coli (Gammaproteobacteria). This unique property of diaphorin may aid microbial mutualism in D. citri, potentially affecting the transmission of "Candidatus Liberibacter spp." (Alphaproteobacteria), the pathogens of the most destructive citrus disease Huanglongbing. Moreover, this property may be exploited to promote microbes' efficiency in producing industrial materials. However, the mechanism underlying this activity is unknown. Diaphorin belongs to the family of pederin-type compounds, which inhibit protein synthesis in eukaryotes by binding to eukaryotic ribosomes. Therefore, as a first step to assess diaphorin's direct influence on bacterial gene expression, this study examined the effect of diaphorin on the in vitro translation using ribosomes of B. subtilis and E. coli, quantifying the production of the green fluorescent protein. The results showed that the gene expression involving B. subtilis and E. coli ribosomes along with five millimolar diaphorin was 29.6% and 13.1%, respectively, less active than the control. This suggests that the diaphorin's adverse effects on B. subtilis are attributed to, at least partly, its inhibitory effects on gene expression. Moreover, as ingredients of the translation system were common other than ribosomes, the greater inhibitory effects observed with the B. subtilis ribosome imply that the ribosome is among the potential targets of diaphorin. On the other hand, the results also imply that diaphorin's positive effects on E. coli are due to targets other than the core machinery of transcription and translation. This study demonstrated for the first time that a pederin congener affects bacterial gene expression.

Candidatus Kirkpatrickella diaphorinae gen. nov., sp. nov., an uncultured endosymbiont identified in a population of Diaphorina citri from Hawaii.

Diaphorina citri is the hemipteran pest and vector of a devastating bacterial pathogen of citrus worldwide. In addition to the two core bacterial endosymbionts of D. citri, Candidatus Carsonella ruddii and Candidatus Profftella armatura, the genome of a novel endosymbiont and as of yet undescribed microbe was discovered in a Hawaiian D. citri population through deep sequencing of multiple D. citri populations. Found to be closely related to the genus Asaia in the family Acetobacteraceae by 16S rRNA gene sequence analysis, it forms a sister clade along with other insect-associated 16S rRNA gene sequences from uncultured bacterium found associated with Aedes koreicus and Sogatella furcifera. Multilocus sequence analysis confirmed the phylogenetic placement sister to the Asaia clade. Despite the culturable Asaia clade being the closest phylogenetic neighbour, attempts to culture this newly identified bacterial endosymbiont were unsuccessful. On the basis of these distinct genetic differences, the novel endosymbiont is proposed to be classified into a candidate genus and species 'Candidatus Kirkpatrickella diaphorinae'. The full genome was deposited in GenBank (accession number CP107052; prokaryotic 16S rRNA OP600170).

DNA degradation in Haplaxius crudus (Hemiptera: Cixiidae) and Diaphorina citri (Hemiptera: Liviidae) on yellow sticky traps in Florida.

Lethal bronzing (LB) and huanglongbing (HLB) are harmful plant diseases causing significant economic losses in Florida agriculture. Both diseases are caused by bacteria that are transmitted by Hemipteran insect vectors. Accurate detection of pathogens within insect vectors can help provide a better understanding of disease epidemiology. Monitoring of the vector of LB is done primarily using sticky traps within palm canopies. However, it is unknown how long pathogen and vector DNA remain intact under field conditions. If significant DNA degradation takes place over the course of days or weeks, there is a possibility of false negatives occurring when detecting pathogens from these surveys. This study determined how long Haplaxius crudus Van Duzee (Hemiptera: Cixiidae) and LB DNA could remain detectable on sticky traps under field conditions in Florida in winter and summer, using PCR and qPCR. Additionally, this study compared the DNA degradation of Diaphorina citri Kuwayama (Hemiptera: Liviidae) and Candidatus Liberibacter asiaticus (CLas), the causal agent of HLB. The results showed that DNA concentration and amplification rate declined as time on sticky traps increased. Degradation varied between different target genes. The amplification rate of insect genes from sticky trap samples suggests that sticky traps should be changed weekly in summer, and every 2 wk in winter for accurate H. crudus detection. Traps should be changed every 4 days for phytoplasma detection. Traps can be changed monthly for accurate D. citri and CLas detection. Based on these results, standard monitoring protocols can be implemented to more accurately detect vectors and pathogens.

The most polyphagous insect herbivore? Host plant associations of the Meadow spittlebug, Philaenus spumarius (L.).

A comprehensive list of all known host plant species utilised by the Meadow Spittlebug (Philaenus spumarius (L.)) is presented, compiled from published and unpublished sources. P. spumarius feeds on 1311 host plants in 631 genera and 117 families. This appears, by a large margin, to be the greatest number of host species exploited by any herbivorous insect. The Asteraceae (222 species) and Rosaceae (110) together account for 25% of all host species. The Fabaceae (76) and Poaceae (73), are nearly tied for third and fourth place and these four families, combined with the Lamiaceae (62), Apiaceae (50), Brassicaceae (43) and Caprifoliaceae (34), comprise about half of all host species. Hosts are concentrated among herbaceous dicots but range from ferns and grasses to shrubs and trees. Philaenus spumarius is an "extreme polyphage", which appears to have evolved from a monophage ancestor in the past 3.7 to 7.9 million years. It is also the primary European vector of the emerging plant pathogen Xylella fastidiosa. Its vast host range suggests that it has the potential to spread X. fastidiosa among multiple hosts in any environment in which both the spittlebug and bacterium are present. Fully 47.9% of all known hosts were recorded in the Xylella-inspired BRIGIT citizen science P. spumarius host survey, including 358 hosts new to the documentary record, 27.3% of the 1311 total. This is a strong demonstration of the power of organized amateur observers to contribute to scientific knowledge.

Geographical survey of the mycobiome and microbiome of Southern California glassy-winged sharpshooters.

The glassy-winged sharpshooter, Homalodisca vitripennis Germar, is an invasive xylem-feeding leafhopper with a devastating economic impact on California agriculture through transmission of the plant pathogen, Xylella fastidiosa. While studies have focused on X. fastidiosa or known symbionts of H. vitripennis, little work has been done at the scale of the microbiome (the bacterial community) or mycobiome (the fungal community). Here, we characterize the mycobiome and the microbiome of H. vitripennis across Southern California and explore correlations with captivity and host insecticide resistance status. Using high-throughput sequencing of the ribosomal internal transcribed spacer 1 region and the 16S rRNA gene to profile the mycobiome and microbiome, respectively, we found that while the H. vitripennis mycobiome significantly varied across Southern California, the microbiome did not. We also observed a significant difference in both the mycobiome and microbiome between captive and wild H. vitripennis. Finally, we found that the mycobiome, but not the microbiome, was correlated with insecticide resistance status in wild H. vitripennis. This study serves as a foundational look at the H. vitripennis mycobiome and microbiome across Southern California. Future work should explore the putative link between microbes and insecticide resistance status and investigate whether microbial communities should be considered in H. vitripennis management practices. IMPORTANCE The glassy-winged sharpshooter is an invasive leafhopper that feeds on the xylem of plants and transmits the devastating pathogen, Xylella fastidiosa, resulting in significant economic damage to California's agricultural system. While studies have focused on this pathogen or obligate symbionts of the glassy-winged sharpshooter, there is limited knowledge of the bacterial and fungal communities that make up its microbiome and mycobiome. To address this knowledge gap, we explored the composition of the mycobiome and the microbiome of the glassy-winged sharpshooter across Southern California and identified differences associated with geography, captivity, and host insecticide resistance status. Understanding sources of variation in the microbial communities associated with the glassy-winged sharpshooter is an important consideration for developing management strategies to control this invasive insect. This study is a first step toward understanding the role microbes may play in the glassy-winged sharpshooter's resistance to insecticides.

Edible and Medicinal Progress of Cryptotympana atrata (Fabricius) in China.

As an important resource insect, the Cryptotympana atrata is widely distributed in the eastern and central parts of China. The cicada slough is one of the traditional crude drugs in East Asia, and the main component is polysaccharide, which has the functions of anti-convulsion, relieving asthma and improving lipid metabolism. The parasitoid fungus Cordyceps cicadae, which grows inside the cicada nymphs and forms the fruiting bodies on the surface of the host's carcass, is also known as the "cicada flower" in China. The Cordyceps cicadae is another old, traditional Chinese medicine, which has been used as a tonic and medicine to nourish and regulate human immunity for centuries. For the further development and utilization of the golden cicada, this paper summarized the C. atrata from the aspects of their biological characteristics, distribution area, life cycle, history of edible and medicinal use, edible methods and nutritional compositions; emphatically introduced the edible and potential medicinal value of the C. atrata; and specifically expounded the research progress of its application. As one popular insect food, the prospects for the development of C. atrata have also been put forward, especially in artificial breeding technology, food safety risk assessment and medicinal value utilization.

Nutrient supplementation by genome-eroded Burkholderia symbionts of scale insects.

Hemipterans are known as hosts to bacterial or fungal symbionts that supplement their unbalanced diet with essential nutrients. Among them, scale insects (Coccomorpha) are characterized by a particularly large diversity of symbiotic systems. Here, using microscopic and genomic approaches, we functionally characterized the symbionts of two scale insects belonging to the Eriococcidae family, Acanthococcus aceris and Gossyparia spuria. These species host Burkholderia bacteria that are localized in the cytoplasm of the fat body cells. Metagenome sequencing revealed very similar and highly reduced genomes (<900KBp) with a low GC content (~38%), making them the smallest and most AT-biased Burkholderia genomes yet sequenced. In their eroded genomes, both symbionts retain biosynthetic pathways for the essential amino acids leucine, isoleucine, valine, threonine, lysine, arginine, histidine, phenylalanine, and precursors for the semi-essential amino acid tyrosine, as well as the cobalamin-dependent methionine synthase MetH. A tryptophan biosynthesis pathway is conserved in the symbiont of G. spuria, but appeared pseudogenized in A. aceris, suggesting differential availability of tryptophan in the two host species' diets. In addition to the pathways for essential amino acid biosynthesis, both symbionts maintain biosynthetic pathways for multiple cofactors, including riboflavin, cobalamin, thiamine, and folate. The localization of Burkholderia symbionts and their genome traits indicate that the symbiosis between Burkholderia and eriococcids is younger than other hemipteran symbioses, but is functionally convergent. Our results add to the emerging picture of dynamic symbiont replacements in sap-sucking Hemiptera and highlight Burkholderia as widespread and versatile intra- and extracellular symbionts of animals, plants, and fungi.

A 'Candidatus Liberibacter solanacearum' Haplotype B-Specific Family of Candidate Bacterial Effectors.

'Candidatus Liberibacter solanacearum' (Lso) is a phloem-limited pathogen associated with devastating diseases in members of the Solanaceae and Apiaceae and vectored by several psyllid species. Different Lso haplotypes have been identified, and LsoA and LsoB are responsible for diseases in Solanaceae crops. Our efforts are aimed at identifying pathogenicity factors used by this bacterium to thrive in different hosts. Bacterial secreted proteins can play a role in host colonization or the manipulation of the host immune responses; these proteins are called effectors. In this study, we identified six LsoB-specific proteins with a conserved secretion motif as well as a conserved N-terminal domain in the mature protein. These proteins had different expression and secretion patterns but a similar subcellular localization in Nicotiana benthamiana leaves, suggesting that they play different roles regardless of their conserved secretion motif. One of these proteins, CKC_04425, was expressed at high levels in the insect vector and the host plant, indicating that it could play a role in both the plant and insect hosts, whereas the others were mainly expressed in the plant. One protein, CKC_05701, was able to efficiently suppress programmed cell death and reactive oxygen species production, suggesting that it may have a virulence role in LsoB-specific pathogenesis.

Seasonal wild dance of dual endosymbionts in the pear psyllid Cacopsylla pyricola (Hemiptera: Psylloidea).

Most sap-feeding insects maintain obligate relationships with endosymbiotic bacteria that provide their hosts with essential nutrients. However, knowledge about the dynamics of endosymbiont titers across seasons in natural host populations is scarce. Here, we used quantitative PCR to investigate the seasonal dynamics of the dual endosymbionts "Candidatus Carsonella ruddii" and "Ca. Psyllophila symbiotica" in a natural population of the pear psyllid Cacopsylla pyricola (Hemiptera: Psylloidea: Psyllidae). Psyllid individuals were collected across an entire year, covering both summer and overwintering generations. Immatures harboured the highest titers of both endosymbionts, while the lowest endosymbiont density was observed in males. The density of Carsonella remained high and relatively stable across the vegetative period of the pear trees, but significantly dropped during the non-vegetative period, overlapping with C. pyricola's reproductive diapause. In contrast, the titer of Psyllophila was consistently higher than Carsonella's and exhibited fluctuations throughout the sampling year, which might be related to host age. Despite a tightly integrated metabolic complementarity between Carsonella and Psyllophila, our findings highlight differences in their density dynamics throughout the year, that might be linked to their metabolic roles at different life stages of the host.

Coupled Oscillators in an Agroecosystem: Integrating Direct and Indirect Effects.

AbstractAgricultural pests are increasingly appreciated as subjects of ecology. One particular case, a pest in coffee production, is analyzed here using the conceptual framework of complex systems, increasingly acknowledged as having an obvious home in the field of ecology, notorious for its complex structures. The particular case analyzed here arguably falls under the control of the complexity of the ecological system rather than of a simple magic bullet of population regulation. The system, which has been under study in southern Mexico for the past quarter century, is analyzed through the lens of neutral oscillations of the classical nondissipative Lotka-Volterra system. Based on three consumer/resource pairs (populations of [1] an ant, [2] a scale insect, [3] a beetle predator of the scale insect, [4] a fungal pathogen of the scale insect, and [5] a fly parasitoid of the ant), this five-dimensional system is well known qualitatively. Coupling all agents through both direct effects and trait-mediated indirect effects, the behavior of the neutral oscillation form of the system reveals a complex set of behaviors, including harmonized invariant sets, chaos, and/or quasiperiodicity. Such behaviors are well-known subjects in the science of complex systems and, it is argued, are ultimately sufficient to effect a degree of regulation on the pest, independent of explicit density-dependent feedback. Control of the system is thus seen as arguably actuated through its complexity, independent of any classic dissipative force.