An overview of plasmid transfer in the plant microbiome.

Plant microbiomes are pivotal for healthy plant physiological development. Microbes live in complex co-association with plant hosts, and interactions within these microbial communities vary with plant genotype, plant compartment, phenological stage, and soil properties, among others. Plant microbiomes also harbor a substantial and diverse pool of mobile genes encoded on plasmids. Several plasmid functions attributed to plant-associated bacteria are relatively poorly understood. Additionally, the role of plasmids in disseminating genetic traits within plant compartments is not well known. Here, we present the current knowledge on the occurrence, diversity, function, and transfer of plasmids in plant microbiomes, emphasizing the factors that could modulate gene transfer in-planta. We also describe the role of the plant microbiome as a plasmid reservoir and the dissemination of its genetic material. We include a brief discussion on the current methodological limitations in studying plasmid transfer within plant microbiomes. This information could be useful to elucidate the dynamics of the bacterial gene pools, the adaptations different organisms have made, and variations in bacterial populations that might have never been described before, particularly in complex microbial communities associated with plants in natural and anthropogenic impacted environments.

Visual attraction of the European tarnished plant bug Lygus rugulipennis (Hemiptera: Miridae) to a water trap with LED light in chrysanthemum greenhouses and olfactory attraction to novel compounds in Y-tube tests.

BACKGROUND: The European tarnished plant bug Lygus rugulipennis Poppius (Hemiptera: Miridae) can cause several types of damage to crops grown in greenhouses and fields, including flower abortion in eggplant, stem and fruit damage in cucumbers, and splits in chrysanthemums. Studies suggest that both male and female L. rugulipennis may be more attracted to traps based on visual attraction than pheromone-based trap. Therefore, the aim of this study was to evaluate the effectiveness of a water trap with LED lights and semiochemicals in trapping L. rugulipennis in the laboratory and greenhouse. RESULTS: The results showed that water traps equipped with white LED light caught 20 - 30 times more bugs than did the sex pheromone-based traps in greenhouse experiment. During the week of peak flight, the LED water trap caught a total of 29 males and females, whereas the sex pheromone caught only one male. Among the semiochemicals tested in a Y-tube, both males and females were attracted to ß-caryophyllene, but not in the presence of the sex pheromone, whereas both males and females were attracted to pentyl butyrate in the presence of the sex pheromone. The pheromone plus bean plant odor was attractive to the insects, suggesting an interaction between plant odor and pheromone. CONCLUSION: Overall, the findings of the study showed that the water trap with LED light could be an effective method for trapping L. rugulipennis in greenhouses. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Regulation of the antennal transcriptome of the dengue vector, Aedes aegypti, during the first gonotrophic cycle.

BACKGROUND: In the light of dengue being the fastest growing transmissible disease, there is a dire need to identify the mechanisms regulating the behaviour of the main vector Aedes aegypti. Disease transmission requires the female mosquito to acquire the pathogen from a blood meal during one gonotrophic cycle, and to pass it on in the next, and the capacity of the vector to maintain the disease relies on a sustained mosquito population. RESULTS: Using a comprehensive transcriptomic approach, we provide insight into the regulation of the odour-mediated host- and oviposition-seeking behaviours throughout the first gonotrophic cycle. We provide clear evidence that the age and state of the female affects antennal transcription differentially. Notably, the temporal- and state-dependent patterns of differential transcript abundance of chemosensory and neuromodulatory genes extends across families, and appears to be linked to concerted differential modulation by subsets of transcription factors. CONCLUSIONS: By identifying these regulatory pathways, we provide a substrate for future studies targeting subsets of genes across disparate families involved in generating key vector behaviours, with the goal to develop novel vector control tools.

Comparative Studies on the Disease Prevalence and Population Dynamics of Ginger Blotch and Brown Blotch Pathogens of Button Mushrooms.

Bacterial blotch is one of the most economically important diseases of button 'mushroom. Knowledge of mechanisms of disease expression, inoculum thresholds, and disease management is limited to the most well-known pathogen, Pseudomonas tolaasii. Recent outbreaks in Europe have been attributed to 'P. gingeri' and P. salomonii for ginger and brown blotch, respectively. Information about their identity, infection dynamics, and pathogenicity is largely lacking. The disease pressure in an experimental mushroom cultivation facility was evaluated for 'P. gingeri' and P. salomonii over varying inoculation densities, casing soil types, environmental humidity, and cultivation cycles. The pathogen population structures in the casing soils were simultaneously tracked across the cropping cycle using highly specific and sensitive TaqMan-quantitative PCR assays. 'P. gingeri' caused disease outbreaks at lower inoculum thresholds (104 CFU/g) in the soil than P. salomonii (105 CFU/g). Ginger blotch generically declined in later harvest cycles, although brown blotch did not. Casing soils were differentially suppressive to blotch diseases, based on their composition and supplementation. Endemic pathogen populations increased across the cultivation cycle although the inoculated pathogen populations were consistent between the first and second flush. In conclusion, 'P. gingeri' and P. salomonii have unique infection and population dynamics that vary over soil types. Their endemic populations are also differently abundant in peat-based casing soils. This knowledge is essential for interpreting diagnostic results from screening mushroom farms and designing localized disease control strategies.

Molecular characterization of Pseudomonas from Agaricus bisporus caps reveal novel blotch pathogens in Western Europe.

BACKGROUND: Bacterial blotch is a group of economically important diseases affecting the cultivation of common button mushroom, Agaricus bisporus. Despite being studied for more than a century, the identity and nomenclature of blotch-causing Pseudomonas species is still unclear. This study aims to molecularly characterize the phylogenetic and phenotypic diversity of blotch pathogens in Western Europe. METHODS: In this study, blotched mushrooms were sampled from farms across the Netherlands, United Kingdom and Belgium. Bacteria were isolated from symptomatic cap tissue and tested in pathogenicity assays on fresh caps and in pots. Whole genome sequences of pathogenic and non-pathogenic isolates were used to establish phylogeny via multi-locus sequence alignment (MLSA), average nucleotide identity (ANI) and in-silico DNA:DNA hybridization (DDH) analyses. RESULTS: The known pathogens "Pseudomonas gingeri", P. tolaasii, "P. reactans" and P. costantinii were recovered from blotched mushroom caps. Seven novel pathogens were also identified, namely, P. yamanorum, P. edaphica, P. salomonii and strains that clustered with Pseudomonas sp. NC02 in one genomic species, and three non-pseudomonads, i.e. Serratia liquefaciens, S. proteamaculans and a Pantoea sp. Insights on the pathogenicity and symptom severity of these blotch pathogens were also generated. CONCLUSION: A detailed overview of genetic and regional diversity and the virulence of blotch pathogens in Western Europe, was obtained via the phylogenetic and phenotypic analyses. This information has implications in the study of symptomatic disease expression, development of diagnostic tools and design of localized strategies for disease management.

Six Multiplex TaqManTM-qPCR Assays for Quantitative Diagnostics of Pseudomonas Species Causative of Bacterial Blotch Diseases of Mushrooms.

Bacterial blotch is a group of economically important diseases of the common button mushroom (Agaricus bisporus). Once the pathogens are introduced to a farm, mesophilic growing conditions (that are optimum for mushroom production) result in severe and widespread secondary infections. Efficient, timely and quantitative detection of the pathogens is hence critical for the design of localized control strategies and prediction of disease risk. This study describes the development of real-time TaqManTM assays that allow molecular diagnosis of three currently prevalent bacterial blotch pathogens: "Pseudomonas gingeri," Pseudomonas tolaasii and (as yet uncharacterized) Pseudomonas strains (belonging to Pseudomonas salomonii and Pseudomonas edaphica). For each pathogen, assays targeting specific DNA markers on two different loci, were developed for primary detection and secondary verification. All six developed assays showed high diagnostic specificity and sensitivity when tested against a panel of 63 Pseudomonas strains and 40 other plant pathogenic bacteria. The assays demonstrated good analytical performance indicated by linearity across calibration curve (>0.95), amplification efficiency (>90%) and magnitude of amplification signal (>2.1). The limits of detection were optimized for efficient quantification in bacterial cultures, symptomatic tissue, infected casing soil and water samples from mushroom farms. Each target assay was multiplexed with two additional assays. Xanthomonas campestris was detected as an extraction control, to account for loss of DNA during sample processing. And the total Pseudomonas population was detected, to quantify the proportion of pathogenic to beneficial Pseudomonas in the soil. This ratio is speculated to be an indicator for blotch outbreaks. The multiplexed assays were successfully validated and applied by routine testing of diseased mushrooms, peat sources, casing soils, and water from commercial production units.

Genome Resource of Two Potato Strains of Ralstonia solanacearum Biovar 2 (Phylotype IIB Sequevar 1) and Biovar 2T (Phylotype IIB Sequevar 25) Isolated from Lowlands in Iran.

Ralstonia solanacearum, the causal agent of bacterial wilt and brown rot disease, is one of the major pathogens of solanaceous crops, including potato, around the globe. Biovar 2T (phylotype II/sequevar 25) of R. solanacearum is adapted to tropical lowlands and is only reported in South America and Iran. Thus far, no genome resource of the biovar 2T of the pathogen has been available. Here, we present the near-complete genome sequences of the biovar 2T strain CFBP 8697 as well as strain CFBP 8695 belonging to biovar 2 race 3, both isolated from potato in Iran. The genomic data of biovar 2T will extend our understanding of the virulence features of R. solanacearum and pave the way for research on biovar 2T functional and interaction genetics.

Blood meal induced regulation of the chemosensory gene repertoire in the southern house mosquito.

BACKGROUND: The southern house mosquito, Culex quinquefasciatus, is one of the most prevalent vectors of lymphatic filariasis and flavivirus-induced encephalitis. Its vectorial capacity is directly affected by its reproductive feeding behaviors, such as host seeking, blood feeding, resting, and egg laying. In mosquitoes, these gonotrophic behaviors are odor-mediated and regulated following blood feeding. Immediately after a blood meal, female mosquitoes show reduced olfactory responsiveness and flight activity, as they enter a resting state. Insights into antennal chemosensory gene regulation at this time period can provide a foundation to identify targets involved in the state switch between host seeking and resting. RESULTS: This study used quantitative gene expression analyses to explore blood meal induced regulation of chemosensory gene families in the antennae of 6 days post-emergence C. quinquefasciatus females. Improved annotations for multiple chemosensory gene families, and a quantitative differential gene expression analysis between host seeking and 24 h post- blood fed females of the same age, allowed for the detection of transcripts that potentially play a role in the switch from host seeking to resting, in C. quinquefasciatus. The expression profiles of chemosensory genes varied significantly between the two treatments. CONCLUSIONS: Annotations for chemosensory gene repertoires in C. quinquefasciatus have been manually curated and corrected for 3' exon choice and transcript length, through sequence and transcriptome analyses. The gene expression analyses identified various molecular components of the peripheral olfactory system in C. quinquefasciatus, including odorant receptors, ionotropic receptors, odorant binding proteins and chemosensory proteins, that are regulated in response to blood feeding, and could be critical for the behavioral switch from host seeking to resting. Functional characterization of these proteins in the future can identify targets essential for the females' gonotrophic behaviors, and can be used to design novel vector control strategies.

Developments and challenges in biodiesel production from microalgae: A review.

The imminent depletion of fossil fuels and the surging global demand for renewable energy have led to the search for nonconventional energy sources. After a few decades of trial and error, the world is now testing the sources of the third generation of fossil fuels, which contain for most parts microalgae. With more than 80% oil content, being adaptable in growth parameters and highly versatile, microalgae are highly promising sources of biofuels in the present time. The present article makes a sweeping attempt to highlight the various methods employed for cultivation of microalgae, techniques to harvest and extract biomass from huge algal cultures, as well as their downstream production and processing procedures. The advantages, limitations, and challenges faced by each of them have been described to some extent. Major concerns pertaining to biofuels are supposed to be their environmental sustainability and economic viability along with their cost effectiveness. This would require a great deal of empirical data on existing systems and a great deal of optimization to generate a more robust one. We have concluded our article with a SWOT analysis of using algae for biodiesel production in a tabulated form.