Vegetative incompatibility in Neurospora: its effect on horizontal transfer of mitochondrial plasmids and senescence in natural populations

1994 ◽  
Vol 26 (2) ◽  
pp. 113-119 ◽  
Author(s):  
Fons Debets ◽  
Xiao Yang ◽  
Anthony J.F. Griffiths
Keyword(s):  
Horizontal Transfer ◽  
Natural Populations ◽  
Vegetative Incompatibility ◽  
Mitochondrial Plasmids

scholarly journals Establishment and maintenance of aphid endosymbionts after horizontal transfer is dependent on host genotype

2017 ◽  
Vol 13 (5) ◽  
pp. 20170016 ◽  
Author(s):  
Benjamin J. Parker ◽  
Ailsa H. C. McLean ◽  
Jan Hrček ◽  
Nicole M. Gerardo ◽  
H. Charles J. Godfray
Keyword(s):  
Natural Selection ◽  
Microbial Communities ◽  
Host Plant ◽  
Intraspecific Variation ◽  
Horizontal Transfer ◽  
Natural Populations ◽  
Host Genotype ◽  
Pea Aphids

Animal-associated microbial communities have important effects on host phenotypes. Individuals within and among species differ in the strains and species of microbes that they harbour, but how natural selection shapes the distribution and abundance of symbionts in natural populations is not well understood. Symbionts can be beneficial in certain environments but also impose costs on their hosts. Consequently, individuals that can or cannot associate with symbionts will be favoured under different ecological circumstances. As a result, we predict that individuals within a species vary in terms of how well they accept and maintain symbionts. In pea aphids, the frequency of endosymbionts varies among host-plant-associated populations (‘biotypes’). We show that aphid genotypes from different biotypes vary in how well they accept and maintain symbionts after horizontal transfer. We find that aphids from biotypes that frequently harbour symbionts are better able to associate with novel symbionts than those from biotypes that less frequently harbour symbionts. Intraspecific variation in the ability of hosts to interact with symbionts is an understudied factor explaining patterns of host–symbiont association.

scholarly journals Evidence for horizontal transmission of the P transposable element between Drosophila species.

Genetics ◽  
1990 ◽  
Vol 124 (2) ◽  
pp. 339-355 ◽  
Author(s):  
S B Daniels ◽  
K R Peterson ◽  
L D Strausbaugh ◽  
M G Kidwell ◽  
A Chovnick
Keyword(s):  
Horizontal Transfer ◽  
Horizontal Transmission ◽  
Natural Populations ◽  
P Element ◽  
Base Substitution ◽  
Potential Donor ◽  
Transfer Event ◽  
P Elements ◽  
Autonomous Element ◽  
Group A

Abstract Several studies have suggested that P elements have rapidly spread through natural populations of Drosophila melanogaster within the last four decades. This observation, together with the observation that P elements are absent in the other species of the melanogaster subgroup, has lead to the suggestion that P elements may have entered the D. melanogaster genome by horizontal transmission from some more distantly related species. In an effort to identify the potential donor in the horizontal transfer event, we have undertaken an extensive survey of the genus Drosophila using Southern blot analysis. The results showed that P-homologous sequences are essentially confined to the subgenus Sophophora. The strongest P hybridization occurs in species from the closely related willistoni group. A wild-derived strain of D. willistoni was subsequently selected for a more comprehensive molecular examination. As part of the analysis, a complete P element was cloned and sequenced from this line. Its nucleotide sequence was found to be identical to the D. melanogaster canonical P, with the exception of a single base substitution at position 32. When the cloned element was injected into D. melanogaster embryos, it was able to both promote transposition of a coinjected marked transposon and induce singed-weak mutability, thus demonstrating its ability to function as an autonomous element. The results of this study suggest that D. willistoni may have served as the donor species in the horizontal transfer of P elements to D. melanogaster.

scholarly journals Genetic Control of Horizontal Virus Transmission in the Chestnut Blight Fungus, Cryphonectria parasitica

Genetics ◽  
2001 ◽  
Vol 159 (1) ◽  
pp. 107-118 ◽  
Author(s):  
Paolo Cortesi ◽  
Charles E McCulloch ◽  
Haiyue Song ◽  
Haiqun Lin ◽  
Michael G Milgroom
Keyword(s):  
Logistic Regression ◽  
Regression Model ◽  
Logistic Regression Model ◽  
Horizontal Transmission ◽  
Natural Populations ◽  
Virus Transmission ◽  
Cryphonectria Parasitica ◽  
Chestnut Blight ◽  
Vegetative Incompatibility ◽  
Chestnut Blight Fungus

Abstract Vegetative incompatibility in fungi has long been known to reduce the transmission of viruses between individuals, but the barrier to transmission is incomplete. In replicated laboratory assays, we showed conclusively that the transmission of viruses between individuals of the chestnut blight fungus Cryphonectria parasitica is controlled primarily by vegetative incompatibility (vic) genes. By replicating vic genotypes in independent fungal isolates, we quantified the effect of heteroallelism at each of six vic loci on virus transmission. Transmission occurs with 100% frequency when donor and recipient isolates have the same vic genotypes, but heteroallelism at one or more vic loci generally reduces virus transmission. Transmission was variable among single heteroallelic loci. At the extremes, heteroallelism at vic4 had no effect on virus transmission, but transmission occurred in only 21% of pairings that were heteroallelic at vic2. Intermediate frequencies of transmission were observed when vic3 and vic6 were heteroallelic (76 and 32%, respectively). When vic1, vic2, and vic7 were heteroallelic, the frequency of transmission depended on which alleles were present in the donor and the recipient. The effect of heteroallelism at two vic loci was mostly additive, although small but statistically significant interactions (epistasis) were observed in four pairs of vic loci. A logistic regression model was developed to predict the probability of virus transmission between vic genotypes. Heteroallelism at vic loci, asymmetry, and epistasis were the dominant factors controlling transmission, but host genetic background also was statistically significant, indicating that vic genes alone cannot explain all the variation in virus transmission. Predictions from the logistic regression model were highly correlated to independent transmission tests with field isolates. Our model can be used to estimate horizontal transmission rates as a function of host genetics in natural populations of C. parasitica.

scholarly journals Plasmid suppressors active in the sexual cycle of Neurospora intermedia.

Genetics ◽  
1993 ◽  
Vol 135 (4) ◽  
pp. 993-1002
Author(s):  
X Yang ◽  
A J Griffiths
Keyword(s):  
Specific Interaction ◽  
Natural Populations ◽  
Sexual Cycle ◽  
Maternal Transmission ◽  
Interaction Type ◽  
Linear Plasmids ◽  
Mitochondrial Plasmids ◽  
Maternal Parent ◽  
Neurospora Intermedia ◽  
Natural Isolates

Abstract We have discovered that, in certain crosses of natural isolates of Neurospora intermedia, linear and circular mitochondrial plasmids of the maternal parent are not transmitted to the progeny. This contrasts with the maternal transmission of organellar genetic elements generally observed in crosses between laboratory strains and between other natural isolates. Formally, failure of plasmid transmission is a type of plasmid suppression. The present cases represent the first report of plasmid suppressors in natural populations of fungi. Strains used as female parents can transmit or not transmit plasmids depending on the strain used as male parent. Males that act to suppress in one cross fail to suppress in others. Therefore, the suppression of plasmids depends on a strain-specific interaction and is not determined exclusively by the males. Since suppression is a specific interaction we inferred that it must be genetically based and tested this hypothesis by seeking segregation of suppressed and nonsuppressed phenotypes in octads. Segregation of the original full suppression of all plasmids was indeed observed in each of the three sets of testcrosses examined. The interaction type of suppression must be initiated in ascogenous tissue during the sexual cycle. It is a nonautonomous type of suppression, affecting all descendent cells. In any one case of suppression, either one, several, or all plasmids can be lost. Both linear and circular plasmids can be eliminated by the same suppressor genotype. In addition, several strains were found to contain suppressors that act after ascospore delineation. This autonomous type of suppression has been observed previously in laboratory strains, but not in natural isolates. All the cases of plasmid suppression identified in this study involved a range of apparently neutral circular and linear plasmids. Using one senescent Kalilo strain of N. intermedia, we did not detect any case of suppression of the senescence-determining linear plasmid kalDNA.

scholarly journals Evidence for “inter- and intraspecific horizontal genetic transfers” between anciently asexual bdelloid rotifers is explained by cross-contamination

2017 ◽  
Author(s):  
Christopher G. Wilson ◽  
Reuben W. Nowell ◽  
Timothy G. Barraclough
Keyword(s):  
Sequence Homology ◽  
Horizontal Transfer ◽  
Natural Populations ◽  
Cross Contamination ◽  
Genetic Transfer ◽  
Genomic Features ◽  
Bdelloid Rotifers ◽  
Maintenance Of Sex ◽  
Nuclear Loci ◽  
Donor Species

SummaryBdelloid rotifers are microscopic invertebrates thought to have evolved for millions of years without sexual reproduction. They have attracted the attention of biologists puzzled by the maintenance of sex among nearly all other eukaryotes. Bdelloid genomes have an unusually high proportion of horizontally acquired non-metazoan genes. This well-substantiated finding has invited speculation that homologous horizontal transfer between rotifers also may occur, perhaps even 'replacing' sex. A 2016 study in Current Biology claimed to supply evidence for this hypothesis. The authors sampled rotifers of the genus Adineta from natural populations and sequenced one mitochondrial and four nuclear loci. For several samples, species assignments were incongruent among loci, which the authors interpreted as evidence of "interspecific genetic exchanges". Here, we use sequencing chromatograms supplied by the authors to demonstrate that samples treated as individuals actually contained two or more divergent mitochondrial and ribosomal sequences, indicating contamination with DNA from additional animals belonging to the supposed “donor species”. We also show that “exchanged” molecules share only 75% sequence homology, a degree of divergence incompatible with established mechanisms of recombination and genomic features of Adineta. These findings are parsimoniously explained by cross-contamination of tubes with animals or DNA from different species. Given the proportion of tubes contaminated in this way, we show by calculation that evidence for "intraspecific horizontal exchange" in the same dataset is explained by contamination with conspecific DNA. On the clear evidence of these analyses, the 2016 study provides no reliable support for the hypothesis of horizontal genetic transfer between or within these bdelloid species.

High-voltage electron microscopy of maxillary gland of spirochete-infected brine shrimp: lesion of efferent tubule

1988 ◽  
Vol 46 ◽  
pp. 362-363
Author(s):  
G. E. Tyson ◽  
M. J. Song
Keyword(s):  
Electron Microscopy ◽  
High Voltage ◽  
Brine Shrimp ◽  
Natural Populations ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron ◽  
High Voltage Electron ◽  
Infected Adult

Natural populations of the brine shrimp, Artemia, may possess spirochete- infected animals in low numbers. The ultrastructure of Artemia's spirochete has been described by conventional transmission electron microscopy. In infected shrimp, spirochetal cells were abundant in the blood and also occurred intra- and extracellularly in the three organs examined, i.e. the maxillary gland (segmental excretory organ), the integument, and certain muscles The efferent-tubule region of the maxillary gland possessed a distinctive lesion comprised of a group of spirochetes, together with numerous small vesicles, situated in a cave-like indentation of the base of the tubule epithelium. in some instances the basal lamina at a lesion site was clearly discontinuous. High-voltage electron microscopy has now been used to study lesions of the efferent tubule, with the aim of understanding better their three-dimensional structure.Tissue from one maxillary gland of an infected, adult, female brine shrimp was used for HVEM study.

Effect of acid deposition on trichome morphology and dogwood anthracnose biology

1992 ◽  
Vol 50 (1) ◽  
pp. 840-841
Author(s):  
Kyle T. Thornham ◽  
R. Jay Stipes ◽  
Randolph L. Grayson
Keyword(s):  
Acid Deposition ◽  
Disease Incidence ◽  
Natural Populations ◽  
Tree Disease ◽  
Flowering Dogwood ◽  
Discula Destructiva ◽  
Disease Induction ◽  
Dogwood Anthracnose ◽  
Trichome Morphology ◽  
Precipitation Events

Dogwood anthracnose, caused by Discula destructiva (1), is another new catastrophic tree disease that has ravaged natural populations of the flowering dogwood (Cornus florida) in the Appalachians over the past 15 years, and the epidemic is prognosticated to continue (2). An estimated 9.5 million acres have been affected, primarily in the Appalachian Mountains, from VA southwards, alone, and an estimated 50% of all dogwoods in PA have been killed. Since acid deposition has been linked experimentally with disease induction, and since the disease incidence and severity are more pronounced at higher elevations where lower pH precipitation events occur, we investigated the effect of acidic foliar sprays on moiphologic changes in the foliar cuticle and trichomes (3), the initial sites of infection and foci of Discula sporulation.

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