scholarly journals An alternative route of bacterial infection associated with a novel resistance locus in the Daphnia–Pasteuria host–parasite system

Heredity ◽  
2020 ◽  
Vol 125 (4) ◽  
pp. 173-183
Author(s):  
Gilberto Bento ◽  
Peter D. Fields ◽  
David Duneau ◽  
Dieter Ebert
Keyword(s):  
Host Resistance ◽  
Natural Populations ◽  
Attachment Site ◽  
Genomic Region ◽  
Infection Process ◽  
Resistance Locus ◽  
Significant Qtls ◽  
Novel Host ◽  
Trait Locus ◽  
Host Parasite

Abstract To understand the mechanisms of antagonistic coevolution, it is crucial to identify the genetics of parasite resistance. In the Daphnia magna–Pasteuria ramosa host–parasite system, the most important step of the infection process is the one in which P. ramosa spores attach to the host’s foregut. A matching-allele model (MAM) describes the host–parasite genetic interactions underlying attachment success. Here we describe a new P. ramosa genotype, P15, which, unlike previously studied genotypes, attaches to the host’s hindgut, not to its foregut. Host resistance to P15 attachment shows great diversity across natural populations. In contrast to P. ramosa genotypes that use foregut attachment, P15 shows some quantitative variation in attachment success and does not always lead to successful infections, suggesting that hindgut attachment represents a less-efficient infection mechanism than foregut attachment. Using a Quantitative Trait Locus (QTL) approach, we detect two significant QTLs in the host genome: one that co-localizes with the previously described D. magna PR locus of resistance to foregut attachment, and a second, major QTL located in an unlinked genomic region. We find no evidence of epistasis. Fine mapping reveals a genomic region, the D locus, of ~13 kb. The discovery of a second P. ramosa attachment site and of a novel host-resistance locus increases the complexity of this system, with implications for both for the coevolutionary dynamics (e.g., Red Queen and the role of recombination), and for the evolution and epidemiology of the infection process.

scholarly journals Quantitative trait locus for resistance to the aphid Rhopalosiphum padi L. in barley (Hordeum vulgare L.) is not linked with a genomic region for gramine concentration

2019 ◽  
Vol 14 (1) ◽  
pp. 57-65
Author(s):  
Malcolm Macaulay ◽  
Luke Ramsay ◽  
Inger Åhman
Keyword(s):  
Hordeum Vulgare ◽  
Rhopalosiphum Padi ◽  
Indole Alkaloid ◽  
Genomic Region ◽  
Grass Species ◽  
Resistance Locus ◽  
Hordeum Vulgare L ◽  
Trait Locus ◽  
Dh Lines ◽  
Do So

Abstract Gramine is an indole alkaloid found in certain grass species. Results of previous studies have diverged as to whether this compound might cause resistance to aphids or not. In a breeding program aiming to introduce resistance to the cereal pest Rhopalosiphum padi L. in barley, a cultivar has been crossed with the progenitor of cultivated barley, Hordeum vulgare ssp. spontaneum, and an F1-derived population of doubled haploid (DH) lines was screened both for seedling gramine concentration and resistance to R. padi. The resistance was measured as individual aphid growth in the laboratory. The present study aims to determine if there is a genetic relationship between aphid growth retardation and gramine concentration. To do so, the lines were genotyped with a 384 SNP oligonucleotide pool assay and QTL analyses were performed for both traits. A previously identified aphid resistance locus on the distal part of chromosome 2HS was thereby confirmed, with resistance inherited from H. v. ssp. spontaneum, whereas one or more QTL for gramine concentration were potentially indicated on chromosome 3H, thus corroborating that the two traits are not linked genetically.

scholarly journals Inferring Linkage Disequilibrium Between a Polymorphic Marker Locus and a Trait Locus in Natural Populations

Genetics ◽  
2000 ◽  
Vol 156 (1) ◽  
pp. 457-467 ◽  
Author(s):  
Z W Luo ◽  
S H Tao ◽  
Z-B Zeng
Keyword(s):  
Linkage Disequilibrium ◽  
Allele Frequency ◽  
Random Mating ◽  
Natural Populations ◽  
Polymorphic Marker ◽  
Marker Locus ◽  
Model Parameters ◽  
Phenotypic Variance ◽  
Wide Range ◽  
Trait Locus

Abstract Three approaches are proposed in this study for detecting or estimating linkage disequilibrium between a polymorphic marker locus and a locus affecting quantitative genetic variation using the sample from random mating populations. It is shown that the disequilibrium over a wide range of circumstances may be detected with a power of 80% by using phenotypic records and marker genotypes of a few hundred individuals. Comparison of ANOVA and regression methods in this article to the transmission disequilibrium test (TDT) shows that, given the genetic variance explained by the trait locus, the power of TDT depends on the trait allele frequency, whereas the power of ANOVA and regression analyses is relatively independent from the allelic frequency. The TDT method is more powerful when the trait allele frequency is low, but much less powerful when it is high. The likelihood analysis provides reliable estimation of the model parameters when the QTL variance is at least 10% of the phenotypic variance and the sample size of a few hundred is used. Potential use of these estimates in mapping the trait locus is also discussed.

scholarly journals Transcriptomic profiling of wheat near-isogenic lines reveals candidate genes on chromosome 3A for pre-harvest sprouting resistance

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Xingyi Wang ◽  
Hui Liu ◽  
Kadambot H. M. Siddique ◽  
Guijun Yan
Keyword(s):  
Candidate Genes ◽  
Quantitative Trait ◽  
Genomic Region ◽  
Nucleotide Polymorphisms ◽  
Near Isogenic Lines ◽  
Gene Effects ◽  
Isogenic Lines ◽  
Trait Locus ◽  
Grain Yield And Quality ◽  
Sprouting Resistance

Abstract Background Pre-harvest sprouting (PHS) in wheat can cause severe damage to both grain yield and quality. Resistance to PHS is a quantitative trait controlled by many genes located across all 21 wheat chromosomes. The study targeted a large-effect quantitative trait locus (QTL) QPhs.ccsu-3A.1 for PHS resistance using several sets previously developed near-isogenic lines (NILs). Two pairs of NILs with highly significant phenotypic differences between the isolines were examined by RNA sequencing for their transcriptomic profiles on developing seeds at 15, 25 and 35 days after pollination (DAP) to identify candidate genes underlying the QTL and elucidate gene effects on PHS resistance. At each DAP, differentially expressed genes (DEGs) between the isolines were investigated. Results Gene ontology and KEGG pathway enrichment analyses of key DEGs suggested that six candidate genes underlie QPhs.ccsu-3A.1 responsible for PHS resistance in wheat. Candidate gene expression was further validated by quantitative RT-PCR. Within the targeted QTL interval, 16 genetic variants including five single nucleotide polymorphisms (SNPs) and 11 indels showed consistent polymorphism between resistant and susceptible isolines. Conclusions The targeted QTL is confirmed to harbor core genes related to hormone signaling pathways that can be exploited as a key genomic region for marker-assisted selection. The candidate genes and SNP/indel markers detected in this study are valuable resources for understanding the mechanism of PHS resistance and for marker-assisted breeding of the trait in wheat.

scholarly journals Genetic Mechanisms Underlying Apimaysin and Maysin Synthesis and Corn Earworm Antibiosis in Maize (Zea mays L.)

Genetics ◽  
1998 ◽  
Vol 149 (4) ◽  
pp. 1997-2006
Author(s):  
E A Lee ◽  
P F Byrne ◽  
M D McMullen ◽  
M E Snook ◽  
B R Wiseman ◽  
...  
Keyword(s):  
Helicoverpa Zea ◽  
Larval Growth ◽  
Corn Earworm ◽  
Phenotypic Variance ◽  
Significant Qtls ◽  
F2 Population ◽  
Genetic Mechanisms ◽  
Trait Locus ◽  
Maize Silks ◽  
Related Compounds

Abstract C-glycosyl flavones in maize silks confer resistance (i.e., antibiosis) to corn earworm (Helicoverpa zea [Boddie]) larvae and are distinguished by their B-ring substitutions, with maysin and apimaysin being the di- and monohydroxy B-ring forms, respectively. Herein, we examine the genetic mechanisms underlying the synthesis of maysin and apimaysin and the corresponding effects on corn earworm larval growth. Using an F2 population, we found a quantitative trait locus (QTL), rem1, which accounted for 55.3% of the phenotypic variance for maysin, and a QTL, pr1, which explained 64.7% of the phenotypic variance for apimaysin. The maysin QTL did not affect apimaysin synthesis, and the apimaysin QTL did not affect maysin synthesis, suggesting that the synthesis of these closely related compounds occurs independently. The two QTLs, rem1 and pr1, were involved in a significant epistatic interaction for total flavones, suggesting that a ceiling exists governing the total possible amount of C-glycosyl flavone. The maysin and apimaysin QTLs were significant QTLs for corn earworm antibiosis, accounting for 14.1% (rem1) and 14.7% (pr1) of the phenotypic variation. An additional QTL, represented by umc85 on the short arm of chromosome 6, affected antibiosis (R2 = 15.2%), but did not affect the synthesis of the C-glycosyl flavones.

Transcript map of the temperate Lactobacillus gasseri bacteriophage ϕadh

Microbiology ◽  
2003 ◽  
Vol 149 (10) ◽  
pp. 2987-2999 ◽  
Author(s):  
Eric Altermann ◽  
Bernhard Henrich
Keyword(s):  
Replication Origin ◽  
Phage Genome ◽  
Attachment Site ◽  
Genomic Region ◽  
Dna Packaging ◽  
Middle Region ◽  
Late Transcription ◽  
Early Transcription ◽  
Transcript Map ◽  
Overlapping Transcripts

Temporal transcription of phage ϕadh was analysed during lytic reproduction. Based on Northern hybridizations the phage genome was divided into regions of early, middle and late transcription. Eight groups of overlapping transcripts, probably originating from common precursors, were distinguished. Early transcription of a 10·9 kb region adjacent to the lytic/lysogenic switch started within the first 10 min of infection and produced three groups of mRNAs mostly related to DNA replication. Four middle transcripts were observed 30 min after infection, corresponding to an 8·5 kb genomic region, which started at the replication origin (ori) and encompassed a DNA packaging function and the cos site. Three groups of late transcripts were first observed 50 min after infection, corresponding to a 21·1 kb region between the middle region and the attachment site (attP), encoding functions for capsid morphogenesis and host cell lysis. A fourth group of late-appearing mRNAs was divergently transcribed from the 3·2 kb section between attP and the lytic/lysogenic switch, including the repressor and integrase genes. Except for one set of early mRNAs, all the transcripts persisted until the end of the reproduction cycle. Two confirmed and two predicted promoters were assigned to transcript 5′ ends in the early region.

scholarly journals Schistosoma mansonicercariae experience influx of macromolecules during skin penetration

Parasitology ◽  
2009 ◽  
Vol 136 (11) ◽  
pp. 1257-1267 ◽  
Author(s):  
J. THORNHILL ◽  
P. M. Z. COELHO ◽  
P. McVEIGH ◽  
A. MAULE ◽  
A. D. JURBERG ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Lucifer Yellow ◽  
Surface Membrane ◽  
Skin Penetration ◽  
Pharyngeal Muscle ◽  
Novel Host ◽  
Host Parasite ◽  
Fluorescent Molecules ◽  
Germinal Mass

SUMMARYWe have observed that when cercariae penetrate the skin of mice, there is influx into their tissues of Lucifer Yellow and certain labelled molecules of up to 20 kDa molecular weight. This observation was made using a variety of fluorescent membrane-impermeant compounds injected into the skin before the application of cercariae. This unexpected phenomenon was investigated further by transforming cercariaein vitroin the presence of the membrane-impermeant compounds and examining the distribution by microscopy. In schistosomula derived from this procedure, the nephridiopore and surface membrane were labelled while the pre- and post-acetabular glands were not labelled. The region associated with the oesophagus within the pharyngeal muscle clearly contained the fluorescent molecules, as did the region adjacent to the excretory tubules and the germinal mass. We used cercariae stained with carmine to aid identification of regions labelled with Lucifer Yellow. Although the mechanism of this influx is unclear, the observation is significant. From it, we can suggest an hypothesis that, during skin penetration, exposure of internal tissues of the parasite to external macromolecules represents a novel host-parasite interface.

Endoparasitism in colonial hosts: patterns and processes

Parasitology ◽  
2007 ◽  
Vol 134 (6) ◽  
pp. 841-852 ◽  
Author(s):  
S. L. L. HILL ◽  
B. OKAMURA
Keyword(s):  
Vertical Transmission ◽  
Environmental Conditions ◽  
Negative Effects ◽  
Temporal Sampling ◽  
Colony Fission ◽  
High Prevalence ◽  
Novel Host ◽  
Patterns And Processes ◽  
Host Parasite ◽  
Lack Of Knowledge

SUMMARYThis study begins to redress our lack of knowledge of the interactions between colonial hosts and their parasites by focusing on a novel host-parasite system. Investigations of freshwater bryozoan populations revealed that infection by myxozoan parasites is widespread. Covert infections were detected in all 5 populations studied and were often at high prevalence while overt infections were observed in only 1. Infections were persistent in populations subject to temporal sampling. Negative effects of infection were identified but virulence was low. Infection did not induce mortality in the environmental conditions studied. However, the production of statoblasts (dormant propagules) was greatly reduced in bryozoans with overt infections in comparison to uninfected bryozoans. Overtly-infected bryozoans also grew more slowly and had low fission rates relative to colonies lacking overt infection. Bryozoans with covert infections were smaller than uninfected bryozoans. High levels of vertical transmission were achieved through colony fission and the infection of statoblasts. Increased fission rates may be a strategy for hosts to escape from parasites but the parasite can also exploit the fragmentation of colonial hosts to gain vertical transmission and dispersal. Our study provides evidence that opportunities and constraints for host-parasite co-evolution can be highly dependent on organismal body plans and that low virulence may be associated with exploitation of colonial hosts by endoparasites.

scholarly journals Relationship between Yield Components and Partial Resistance to Lecanicillium fungicola in the Button Mushroom, Agaricus bisporus, Assessed by Quantitative Trait Locus Mapping

2012 ◽  
Vol 78 (7) ◽  
pp. 2435-2442 ◽  
Author(s):  
Marie Foulongne-Oriol ◽  
Anne Rodier ◽  
Jean-Michel Savoie
Keyword(s):  
Quantitative Trait ◽  
Wild Strain ◽  
Genomic Region ◽  
Yield Component ◽  
Phenotypic Variance ◽  
Button Mushroom ◽  
Content Type ◽  
Dry Bubble ◽  
Trait Locus ◽  
Genomic Regions

ABSTRACTDry bubble, caused byLecanicillium fungicola, is one of the most detrimental diseases affecting button mushroom cultivation. In a previous study, we demonstrated that breeding for resistance to this pathogen is quite challenging due to its quantitative inheritance. A second-generation hybrid progeny derived from an intervarietal cross between a wild strain and a commercial cultivar was characterized forL. fungicolaresistance under artificial inoculation in three independent experiments. Analysis of quantitative trait loci (QTL) was used to determine the locations, numbers, and effects of genomic regions associated with dry-bubble resistance. Four traits related to resistance were analyzed. Two to four QTL were detected per trait, depending on the experiment. Two genomic regions, on linkage group X (LGX) and LGVIII, were consistently detected in the three experiments. The genomic region on LGX was detected for three of the four variables studied. The total phenotypic variance accounted for by all QTL ranged from 19.3% to 42.1% over all traits in all experiments. For most of the QTL, the favorable allele for resistance came from the wild parent, but for some QTL, the allele that contributed to a higher level of resistance was carried by the cultivar. Comparative mapping with QTL for yield-related traits revealed five colocations between resistance and yield component loci, suggesting that the resistance results from both genetic factors and fitness expression. The consequences for mushroom breeding programs are discussed.

scholarly journals Characterization of three soybean landraces resistant to Asian soybean rust disease

2020 ◽  
Vol 40 (6) ◽  
Author(s):  
Luciano Nobuhiro Aoyagi ◽  
Yukie Muraki ◽  
Naoki Yamanaka
Keyword(s):  
Susceptible Variety ◽  
Soybean Rust ◽  
Resistance Locus ◽  
Chromosome 6 ◽  
Phakopsora Pachyrhizi ◽  
Rust Disease ◽  
Asian Soybean Rust ◽  
The World ◽  
Trait Locus

Abstract Phakopsora pachyrhizi is an obligatory biotrophic fungus that causes Asian soybean rust (ASR) disease. ASR control primarily involves chemical control and the use of resistant soybean cultivars carrying an Rpp (resistance to P. pachyrhizi) gene. This study aimed to characterize the ASR resistance of three soybean Asian landraces. By screening the world core collection (WC) of soybean, which consists of 80 varieties, three landraces were identified in Southeast Asia as resistant to ASR. Genetic mapping using the F2 population derived from a cross with an ASR-susceptible variety, BRS 184, indicated that KS 1034 (WC2) has ASR resistance conferred by a single dominant resistance gene, mapped on chromosome 18, in the same region where Rpp1 was mapped previously. The BRS 184 × WC61 (COL/THAI/1986/THAI-80) F2 population, on the other hand, showed an ASR resistance locus mapped by quantitative trait locus analysis on chromosome 6, in the region where the resistance conferred by PI 416764 Rpp3 resides, with a logarithm of the odds score peak at the same position as the marker, Satt079, while the BRS 184 × WC51 (HM 39) population showed the resistance to ASR allocated between Satt079 and Sat_263 markers, also in the region where Rpp3 was mapped previously. Both WC51 and WC61 have the same infection profile as FT-2 and PI 462312 when tested against the same ASR isolate panel. These three WCs can be used in MAS programs for introgression of Rpp1 and Rpp3 and the development of ASR-resistant cultivars in the breeding program.

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