Transgenic crops that produce insecticidal proteins from Bacillus thuringiensis (Bt) have provided control of some key pests since 1996. However, the evolution of resistance by pests reduces the ...benefits of Bt crops. Resistance to Bt crops that is not recessively inherited is especially challenging to manage. Here we analyzed nonrecessive resistance to Bt toxin Cry1Ac in eight field populations of Helicoverpa armigera sampled in 2018 from northern China, where this global pest has been exposed to Cry1Ac in Bt cotton since 1997. Bioassays revealed 7.5% of field-derived larvae were resistant to Cry1Ac of which 87% had at least one allele conferring nonrecessive resistance. To analyze this nonrecessive resistance, we developed and applied a variant of a genomic mapping approach called quantitative trait locus (QTL)-seq. This analysis identified a region on chromosome 10 associated with nonrecessive resistance to Cry1Ac in all 21 backcross families derived from field-collected moths. Individual sequencing revealed that all 21 field-collected resistant grandparents of the backcross families had a previously identified dominant point mutation in the tetraspanin gene HaTSPAN1 that occurs in the region of chromosome 10 identified by QTL-seq. QTL-seq also revealed a region on chromosome 26 associated with nonrecessive resistance in at most 14% of the backcross families. Overall, the results imply the point mutation in HaTSPAN1 is the primary genetic basis of nonrecessive resistance to Cry1Ac in field populations of H. armigera from northern China. Moreover, because nonrecessive resistance is predominant, tracking the frequency of this point mutation could facilitate resistance monitoring in the region.
Endophytes live asymptomatically within many cool‐season grasses for at least a portion of their life cycle. Although the leaf endophyte effects on the growth and stress resistance of host grasses ...have been relatively well studied, less attention has been focused on how this relationship may impact soil microbial communities, especially arbuscular mycorrhizal fungi (AMF). We defined endophyte‐infected and endophyte‐free Leymus chinensis as the host grass and neighbouring Stipa krylovii, which was not infected by endophytes, as the non‐host grass. Our objective was to examine the effect of endophyte infection on the colonization rate and composition of AMF communities in both the rhizosphere and bulk soils of their host (L. chinensis) and a neighbouring non‐host (S. krylovii) by a consecutive 2‐year survey. We described AMF communities using high‐throughput DNA sequencing, quantified the proportion of root length colonized by AMF using microscopy, and estimated AMF biomass using a lipid biomarker. Structural equation modelling (SEM) was applied to disentangle the direct and indirect effects (mediated by multiple environmental factors) of an endophyte on AMF. We found that endophyte infection significantly increased colonization rates and rhizosphere soil biomass of AMF but had no significant effect on the bulk soil around the host grass. The endophyte increased the diversity of the rhizosphere soil AMF community by decreasing the abundance of the dominant species Glomus while increasing the abundance of some unidentified AMF. SEM showed that the endophyte effects on AMF biomass in rhizosphere soil were primarily mediated by soil total carbon, total nitrogen and pH. With respect to the non‐host grass, the endophyte infection of host grass did not change the colonization rates or AMF biomass in either the rhizosphere or bulk soil but did cause a shift in the rhizosphere soil AMF community composition, resulting in a decrease in the relative abundance of Septoglomus and an increase in the relative abundance of some unidentified AMF.
Highlights
Effects of endophyte infection on AMF communities in both the rhizosphere and bulk soils were studied.
Endophyte effect was studied not only on the host but also on the non‐host grass.
Endophyte infection significantly increased colonization rates and rhizosphere soil biomass of AMF.
Endophyte effect on AMF biomass in rhizosphere soil was primarily mediated by soil physicochemical properties.
Assessments of bacterial community diversity and dynamics are fundamental for the understanding of microbial ecology as well as biotechnological applications. We show that the choice of PCR primers ...has great impact on the results of analyses of diversity and dynamics using gene libraries and DNA fingerprinting. Two universal primer pairs targeting the 16S rRNA gene, 27F&1492R and 63F&M1387R, were compared and evaluated by analyzing the bacterial community in the activated sludge of a large-scale wastewater treatment plant. The two primer pairs targeted distinct parts of the bacterial community, none encompassing the other, both with similar richness. Had only one primer pair been used, very different conclusions had been drawn regarding dominant phylogenetic and putative functional groups. With 27F&1492R, Betaproteobacteria would have been determined to be the dominating taxa while 63F&M1387R would have described Alphaproteobacteria as the most common taxa. Microscopy and fluorescence in situ hybridization analysis showed that both Alphaproteobacteria and Betaproteobacteria were abundant in the activated sludge, confirming that the two primer pairs target two different fractions of the bacterial community. Furthermore, terminal restriction fragment polymorphism analyses of a series of four activated sludge samples showed that the two primer pairs would have resulted in different conclusions about community stability and the factors contributing to changes in community composition. In conclusion, different PCR primer pairs, although considered universal, target different ranges of bacteria and will thus show the diversity and dynamics of different fractions of the bacterial community in the analyzed sample. We also show that while a database search can serve as an indicator of how universal a primer pair is, an experimental assessment is necessary to evaluate the suitability for a specific environmental sample.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Bouvardia ternifolia
is a medicinal plant considered a source of therapeutic compounds, like the antitumoral cyclohexapeptide bouvardin. It is known that large number of secondary metabolites ...produced by plants results from the interaction of the host and adjacent or embedded microorganisms. Using high-throughput DNA sequencing of V3-16S and V5-18S ribosomal gene libraries, we characterized the endophytic, endophytic + epiphyte bacterial, and fungal communities associated to flowers, leaves, stems, and roots, as well as the rhizosphere. The Proteobacteria (average 80.7%) and Actinobacteria (average 14.7%) were the most abundant bacterial phyla, while Leotiomycetes (average 54.8%) and Dothideomycetes (average 27.4%) were the most abundant fungal classes. Differential abundance for the bacterial endophyte group showed a predominance of
Erwinia
,
Propionibacterium
, and
Microbacterium
genera, while
Sclerotinia
,
Coccomyces
, and
Calycina
genera predominated for fungi. The predictive metagenome analysis for bacteria showed significative abundance of pathways for secondary metabolite production, while a FUNguild analysis revealed the presence of pathotroph, symbiotroph, and saprotrophs in the fungal community. Intra and inter copresence and mutual exclusion interactions were identified for bacterial and fungal kingdoms in the endophyte communities. This work provides a description of the diversity and composition of bacterial and fungal microorganisms living in flowers, leaves, stems, roots, and the rhizosphere of this medicinal plant; thus, it paves the way towards an integral understanding in the production of therapeutic metabolites.
The Lake Tana Labeobarbus species flock represents one of the world's most famous examples of lacustrine species radiations. Previous studies of this group have resulted in the description of at ...least 15 species based on their differences in functional morphology and definition of two clades (lacustrine and riverine spawning clades) based on life history traits. A total of 166 fish representing 14 Labeobarbus species were genotyped using 10 lineage-specific hexaploid microsatellite loci. Six of these loci were developed for this study based on DNA sequence contigs derived from a microsatellite-enriched genomic library of Labeobarbus intermedius from Lake Tana; the remaining four loci were obtained from a previous study. The genotypes of the 10 loci were analyzed to examine genetic diversity and population structure within Lake Tana Labeobarbus. Overall mean allelic richness (NA) was 17.6 alleles per locus and observed (Ho) and expected (He) heterozygosities were 0.84 ± 0.14 and 0.73 ± 0.09, respectively, across all Lake Tana Labeobarbus samples examined. Our analyses reveal that there is little genetic differentiation among species (FST = 0.020-0.099; only 10 of 91 species comparisons were significant), but moderate differentiation (FST = 0.11, p < 0.05) between lacustrine and riverine spawning populations. Relative to previous phylogenetic hypotheses, our phenetic analysis employing the R-based Analysis of Phylogenetics and Evolution (APE) program seems to perform marginally better in revealing lineages within Lake Tana Labeobarbus. Herein, our results are compared to a previous microsatellite-based study of the same populations.
Carpophilus truncatus Murray 1864, is a species of sap beetle which has been recorded from many countries worldwide, and has become recognised as an important pest of nuts. In this study, we present ...a re-description of C. truncatus including diagnostic photographic images of the adults and larvae, and demonstrate that Carpophilus jarijari Powell & Hamilton, 2019 is a junior subjective synonym of C. truncatus. Information about the species' distribution in Australia is updated. DNA barcode sequence data for C. truncatus is reviewed and augmented to enable differentiation from other morphologically similar Carpophilus species that are associated with nuts as hosts, including the cosmopolitan Carpophilus dimidiatus (Fabricius, 1792), for which C. truncatus has sometimes been misidentified. This analysis revealed that existing reference DNA sequences of "C. dimidiatus" consist of three highly genetically divergent lineages, representing three species: the cosmopolitan C. dimidiatus, the widespread C. truncatus, and a newly described species, Carpophilus imitatus sp. nov., known from south-eastern Asia and Australia.
Alveolar echinococcosis (AE), caused by Echinococcus multilocularis, is one of the most important zoonotic diseases. The parasite has a heterogeneous life cycle; more than 40 small mammal species ...have been determined to be potential intermediate hosts worldwide. Turkey is one of the highest endemic countries for AE, but only limited information is available concerning the transmission biology of E. multilocularis. The study aimed to provide data on potential intermediate host species (focus on genus Microtus) across Turkey involved in E. multilocularis transmission to foxes, which is a risk for public health. Trapping sites have been specially selected considering field voles' habitats and ecological requirements. In total, 843 rodents were collected from 141 locations. The metacestodes and lesions of AE were identified as macroscopy and microscopy and confirmed by PCR and DNA sequencing. Seventeen (2.0%) small mammals from 13 (9.2%) locations were found infected with E. multilocularis. Infected individuals were identified as Microtus irani, Microtus mystacinus, Microtus hartingi, Microtus guentheri, Cricetulus migratorius and Mus macedonicus. M. hartingi and M. macedonicus are documented for the first time as intermediate hosts of E. multilocularis. In conclusion, 15 of 17 infected small mammals were found in the Microtus genus. Therefore, the genus Microtus, which inhabits fields near villages and is potential prey for foxes, could be considered an important intermediate host for E. multilocularis across Turkey.
Several economically important pathogens, including species of Chrysoporthe, pose a threat to the rapidly expanding eucalypt plantation industry in Southeast Asia. During 2019 disease surveys in Riau ...and Kalimantan (Indonesia), cankers were observed on eucalypt trees and a collection of fungal isolates was obtained from them. The aim of this study was to confirm the identity of the isolates and to evaluate their relative pathogenicity on different eucalypt clones. Using the DNA sequence data based on the internal transcribed spacer (ITS) region of the ribosomal DNA and two regions of the β-tubulin gene (TUB1 and TUB2), 31 fungal isolates were identified as C. deuterocubensis. Pathogenicity trials showed that C. deuterocubensis isolates differed in their pathogenicity and that different eucalypt genotypes differed in their susceptibility to the pathogen. These results will provide valuable information to reduce the threat of stem canker to future eucalypt plantation development.
Onchocerca volvulus is a filarial parasite that is a major cause of dermatitis and blindness in endemic regions primarily in sub-Saharan Africa. Widespread efforts to control the disease caused by O. ...volvulus infection (onchocerciasis) began in 1974 and in recent years, following successful elimination of transmission in much of the Americas, the focus of efforts in Africa has moved from control to the more challenging goal of elimination of transmission in all endemic countries. Mass drug administration (MDA) with ivermectin has reached more than 150 million people and elimination of transmission has been confirmed in four South American countries, with at least two African countries having now stopped MDA as they approach verification of elimination. It is essential that accurate data for active transmission are used to assist in making the critical decision to stop MDA, since missing low levels of transmission and infection can lead to continued spread or recrudescence of the disease.
Current World Health Organization guidelines for MDA stopping decisions and post-treatment surveillance include screening pools of the Simulium blackfly vector for the presence of O. volvulus larvae using a PCR-ELISA-based molecular technique. In this study, we address the potential of an updated, practical, standardized molecular diagnostic tool with increased sensitivity and species-specificity by comparing several candidate qPCR assays. When paired with heat-stable reagents, a qPCR assay with a mitochondrial DNA target (OvND5) was found to be more sensitive and species-specific than an O150 qPCR, which targets a non-protein coding repetitive DNA sequence. The OvND5 assay detected 19/20 pools of 100 blackfly heads spiked with a single L3, compared to 16/20 for the O150 qPCR assay.
Given the improved sensitivity, species-specificity and resistance to PCR inhibitors, we identified OvND5 as the optimal target for field sample detection. All reagents for this assay can be shipped at room temperature with no loss of activity. The qPCR protocol we propose is also simpler, faster, and more cost-effective than the current end-point molecular assays.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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