Analysis Of F2 Progeny Research Articles

Toxoplasma effector MAF1 mediates recruitment of host mitochondria and impacts the host response.

Author SummaryRecent discoveries have revealed the remarkable functional diversity of mitochondria in roles other than energy production, including an integral role for mitochondria and their dynamics in the regulation of the innate immune response. Interestingly, host mitochondria are recruited to the membranes that surround certain intracellular bacteria and parasites during infection. To date, how and why this phenomenon occurs has been a mystery, although it has been proposed to provide a metabolic benefit to the microbes. Here we identify mitochondrial association factor 1 (MAF1) as the parasite protein that mediates the association between the protozoan pathogen Toxoplasma and host mitochondria during infection. We show that MAF1 is needed to recruit host mitochondria to the Toxoplasma-containing vacuole and that this process is associated with changes in the immune response in infected cells and animals. These findings show that recruitment and association with host mitochondria is an important means by which intracellular pathogens interface with their host. We also find that the cost–benefit outcome of altering mitochondrial function might differ between strains depending on the precise niche in which they evolved; for infectious agents, these differences likely reflect different host organisms.

Physiological differences between lean and siscowet lake trout morphotypes: Are these metabolotypes?

Results of a past study on lean and siscowet lake trout (Salvelinus namaycush) reared under identical conditions from conception indicated that differences in growth and morphometry between these morphotypes have a genetic basis. Using these cultured lake trout, we found that siscowet lake trout had higher lipid levels and lower glycogen levels as compared with lean lake trout in skeletal muscle and liver. Lean lake trout also had higher circulating levels of lipids and glucose compared with siscowet lake trout. Analysis of F1progeny from crosses of the cultured morphotypes showed that progeny of crosses between siscowet females and siscowet males had higher lipid levels than all other crosses. The combined results indicate that the lake trout morphotypes differ substantially in the storage of energy, which may be related to their specific life histories. Siscowets store energy preferentially as lipid and appear to be more efficient in moving lipid from the blood into the muscle and liver. The lipid in siscowets may be adaptive for regulating buoyancy as well as an essential energy reserve for reproduction.

Molecular mapping of black rot resistance locusXca1boon chromosome 3 inIndian cauliflower (Brassica oleraceavar.botrytisL.)

AbstractBlack rot is the most devastating disease of cauliflower worldwide causing severe damage to crop. The identification of markers linked to loci that control resistance can facilitate selection of plants for breeding programmes. In the present investigation,F2population derived from a cross between ‘PusaHimjyoti’, a susceptible genotype, and ‘BR‐161’, a resistant genotype, was phenotyped by artificial inoculation usingXccrace 1. Segregation analysis ofF2progeny indicated that a single dominant locus governed resistance toXccrace 1 in ‘BR‐161’. Bulk segregant analysis in resistant and susceptible bulks ofF2progeny revealed seven differentiating polymorphic markers (threeRAPD, twoISSRand twoSSR) of 102 markers screened. Subsequently, these markers were used to genotype the entire F2population, and a genetic linkage map covering 74.7 cM distance was developed. The major locusXca1bowas mapped in 1.6‐cM interval flanked by the markersRAPD04833andISSR11635. TheXca1bolocus was located on chromosome 3. The linked markers will be useful for marker‐assisted resistance breeding in cauliflower.

Production of a Natural Antibody to the Mouse Polyoma Virus Is a Multigenic Trait

MA/MyJ mice express a natural antibody to the highly oncogenic polyoma virus. C57BR/cdJ mice lack this antibody but mount an adaptive T-cell response to the virus. Analysis of F2 progeny of a cross between these strains reveals a pattern of inheritance of expression of the natural antibody involving two genes in an epistatic relationship.

Genetic Dissection of Basal Resistance to Pseudomonas syringae pv. phaseolicola in Accessions of Arabidopsis

We have examined the genetics of nonhost resistance in Arabidopsis, using the bean pathogen Pseudomonas syringae pv. phaseolicola race 6 1448A to probe accessions for natural variation in basal defense. Symptoms rarely developed in leaves of Niedersenz (Nd), some yellowing and occasional necrosis developed in Columbia (Col), whereas tissue collapse was observed in Wassilewskija (Ws) after inoculation by infiltration. Analysis of F2 progeny and recombinant inbred lines (RIL) from a cross between Col and Nd revealed a pattern of continuous symptom increase, indicating the operation of quantitative determinants of resistance. By mapping quantitative trait loci (QTL), significant linkage was determined for resistance (low symptom score) to markers on chromosome 4. Segregation in the F2 cross from Nd × Ws indicated the operation of two dominant genes for resistance, one of which was FLS2 encoding the flagellin receptor. The requirement for FLS2 to confer resistance was confirmed by transgenic experiments, and we showed that the response to P. syringae pv. phaseolicola was affected by FLS2 gene dosage. Using RIL, the second locus was mapped as a QTL to a large interval on chromosome 1. Both FLS2 and the QTL on chromosome 1 were required for the highest level of resistance to bacterial colonization and symptom development in Nd.

Susceptibility to astrocytoma in mice mutant for Nf1 and Trp53 is linked to chromosome 11 and subject to epigenetic effects.

Astrocytoma is the most common malignant brain tumor in humans. Loss of the p53 signaling pathway and up-regulation of the ras signaling pathway are common during tumor progression. We have shown previously that mice mutant for Trp53 and Nf1 develop astrocytoma, progressing to glioblastoma, on a C57BL/6J strain background. In contrast, here we present data that mice mutant for Trp53 and Nf1 on a 129S4/SvJae background are highly resistant to developing astrocytoma. Through analysis of F1 progeny, we demonstrate that susceptibility to astrocytoma is linked to chromosome 11, and that the modifier gene(s) responsible for differences in susceptibility is closely linked to Nf1 and Trp53. Furthermore, this modifier of astrocytoma susceptibility is itself epigenetically modified. These data demonstrate that epigenetic effects can have a strong effect on whether cancer develops in the context of mutant ras signaling and mutant p53, and that this mouse model of astrocytoma can be used to identify modifier phenotypes with complex inheritance patterns that would be unidentifiable in humans. Because analysis of gene function in the mouse is often performed on a mixed C57BL/6,129 strain background, these data also provide a powerful example of the potential of these strains to mask interesting gene functions.

SNP-based codominant markers for a recessive gene conferring resistance to corky root rot (Rhizomonas suberifaciens) in lettuce (Lactuca sativa).

The analysis of F2 progeny and derived F3 families of Lactuca sativa segregating for resistance to corky root rot caused by Rhizomonas suberifaciens permitted the identification of restriction fragment length polymorphism (RFLP) and single nucleotide polymorphism (SNP) markers linked to the recessive resistance gene cor. PCR-based markers were identified by bulked segregant analysis (BSA). Allele-specific primers were generally designed with the 3 terminal base coinciding with an SNP, matching one of the alleles and mismatching the other, and with an additional subterminal 3 base mismatching both alleles. Codominant, robust, and inexpensive molecular markers were obtained that used standardized PCR conditions. Some of the markers could be analyzed in multiple Lactuca mapping populations that did not segregate for disease resistance allowing the cor locus to be located on several maps. The consistent low density of markers around cor in these maps suggests that cor may be in an area with an elevated rate of recombination. Evaluation of these markers in a large sample of cultivars and landraces identified pairs of flanking polymorphic markers that can be used for marker-assisted selection of corky root resistance.

Recurrent allelic imbalance at the rat Pten locus in DMBA‐induced fibrosarcomas

The tumor-suppressor gene PTEN (phosphatase and tensin homolog) is frequently inactivated in different types of human tumors. Less is known about the involvement of the homologous gene Pten in animal model systems of cancer. By sequencing one of the introns of rat Pten, we found an informative intragenic PCR marker suitable for genetic studies. Through use of this marker, the position of Pten in the genetic linkage map was localized to the distal part of rat chromosome 1 (RNO1) by analysis of F2 progeny from an intercross between inbred strains BN and LE. Subsequently, 22 markers from this region (including the intragenic Pten marker) were used to study the occurrence of allelic imbalance in distal RNO1 in fibrosarcomas that had been induced by DMBA in F1(BNxLE) rats. The analysis revealed that allelic imbalance was common in the vicinity of Pten, and there was loss or reduction of one of the Pten alleles in more than 60% of the fibrosarcomas. DNA sequencing was preformed to investigate whether the Pten allele remaining in the tumors was inactivated by mutation. However, no mutations were detected in the genomic sequence of Pten exons 5 to 9 in any of the fibrosarcomas, and normal mRNA transcripts were expressed in all tumors. Thus, based on the targeted selection for loss of Pten observed in some of these tumors and the absence of inactivation of the remaining allele, we suggest that haploinsufficiency of Pten may be an important factor in rat DMBA-induced fibrosarcomas.

The genetic basis of floral variation in Senecio jacobaea (Asteraceae).

The self-incompatible composite Senecio jacobaea (ragwort) exhibits geographic variation in the frequency of rayed and discoid (rayless) individuals. Hybrid progenies from within- and between-morph crosses were established in a seminatural (garden) environment to determine whether patterns of segregation conform to single-gene predictions (as found in other Senecio species), whether the direction of dominance is conducive to rapid evolutionary change in ray morphology, and whether geographically distant populations of the discoid morph utilize the same or different genes to suppress ray development. Data from segregating F2 and BC families were consistent with a genetic model involving one major locus and an unknown number of modifiers. Analysis of F1 progenies from different intermorph crosses using the same rayed plant as a seed parent revealed a variable and incomplete pattern of dominance, with a trend toward partial dominance in some crosses. Hybridizations between discoid populations produced a few rayed progeny (4%), but there was no tendency for the frequency of rayed progeny to increase with the geographic distance separating the parent populations. Results of this study indicate that major mutations have been important for the evolution of discoid populations of ragwort, that ray-suppressing mutations should be directly available to selection in most populations, and that the suppression of rays is conditioned by the same or similar gene(s) in Atlantic and Baltic populations of the discoid taxon.

Inheritance of Biomass and Crude Drug Content in Black Henbane (Hyoscyamus niger L.)

ABSTRACT The genetics/inheritance of biomass and crude drug content in terms of gene action, genetic variance components, and allied genetic parameters was determined in black/Indian henbane (Hyoscyamus niger) by dialiel analysis of F1 progenies from six parents. The additive (D) and dominance (H1) components were significant for both biomass and crude drug. Epistasis was almost absent and the degree of dominance was in the range of dominance. Dominant alleles caused low and recessive alleles caused high expression of biomass and crude drug. Because of better breeding value, high per-se performance, and desirable position in the Wr-Vr graph, three parents, Aela, Aekla, and Rb were identified as potential genotypes to be exploited for crop improvement by hybridization followed by selection.

Larval paternity and male reproductive success of a broadcast-spawning gorgonian, Plexaura kuna

Male reproductive success of the broadcast-spawning gorgonian, Plexaura kuna Lasker, Kim and Coffroth, 1996, was measured in June 1994 and June and July 1995 at two sites in the San Blas Islands, Panama in order to determine the environmental and biotic factors affecting individual reproductive success. Developing embryos were collected in the field during natural spawning events, and paternity determined using randomly amplified polymorphic DNA markers. Analyses of F1 progeny from defined laboratory matings established that the markers were inherited in Mendelian fashion, and allowed the determination of the zygosities of the markers. P. kuna is clonal, but male reproductive success was not strictly proportional to clone size. Proximity to females appeared to have a greater effect on male reproductive success than clone size, and on both reefs the most successful male clone was the one closest to the spawning female clone. Current direction and transport of gametes by eddies explained variation in paternity assignments between nights. Clonal propagation allows clones to grow and spread toward each other, and may enhance male reproductive success.

Molecular and genetic analyses of the B type surface protein gene from Paramecium tetraurelia.

The gene encoding the B type variable surface protein from Paramecium tetraurelia stock 51 has been cloned and sequenced. The 7,182 nucleotide open reading frame contains no introns and encodes a cysteine-rich protein that has a periodic structure including three nearly perfect tandem repeats in the central region. Interestingly, the B gene is located near a macronuclear telomere as was shown previously for two other paramecium surface protein genes. In this paper, we characterize four independent mutants with complete macronuclear deletions of the B gene. Previous analysis of different macronuclear deletion mutants of the A surface protein gene demonstrated two types of inheritance: typical Mendelian segregation (as illustrated by d12) and cytoplasmic inheritance (shown by d48). F1 analysis of four B- mutants crossed with wild-type cells reveals heterozygous F1 cell lines derived from both parental cytoplasms contain approximately the same copy number of the B gene, as expected for a recessive Mendelian mutation. Analysis of F2 progeny from three of these four B- mutant crosses indicates that one of the three exhibits a Mendelian 1:1 segregation ratio of B+ and B- cell lines. The other two show a preponderance of B+ cells, but this is not correlated with the parental cytoplasmic type. In addition to having a large number of B+ individuals, the d12.144, A-, B- mutant produced some F2 progeny that stably maintain less than normal macronuclear amounts of the A gene and/or the B gene.

RELP markers linked to two Hessian fly-resistance genes in wheat (Triticum aestivum L.) from Triticum tauschii (coss.) Schmal

Restriction fragment length polymorphism (RFLP) markers linked to genes controlling Hessian fly resistance from Triticum tauschii (Coss.) Schmal. were identified for two wheat (Triticum aestivum L.) germ plasm lines KS89WGRC3 (C3) and KS89WGRC6 (C6). Forty-six clones with loci on chromosomes of homoeologous group 3 and 28 clones on those of group 6 were surveyed for polymorphisms. Eleven and 12 clones detected T. tauschii loci in the two lines, respectively. Analysis of F2 progenies indicated that the Hessian fly resistance gene H23 identified in C3 is linked to XksuH4 (6.9 cM) and XksuG48 (A) (15.6 cM), located on 6D. The resistance gene H24 in C6 is linked to XcnlBCD451 (5.9 cM), XcnlCD0482 (5.9 cM) and XksuG48 (B) (12.9 cM), located on 3DL.

Genetic analysis of recessive primordiumless mutants in the basidiomyceteCoprinus cinereus

Four recessive primordiumless mutants from anAmut Bmut strain ofCoprinus cinereus were crossed with wild-type strain. Segregation analysis of F1-progeny and complementation test showed that these mutations were controlled by 4 single recessive genes. All these genes were unlinked to both theA andB factors.

MHC and non-MHC genes regulate elimination of lymphocytic choriomeningitis virus and antiviral cytotoxic T lymphocyte and delayed-type hypersensitivity mediating T lymphocyte activity in parallel.

The course of systemic infection with lymphocytic choriomeningitis virus was studied in mouse strains differing in the MHC or non-MHC background. Virus clearance rates differed significantly between H-2 identical strains as well as between congenic strains differing in the H-2L subregion, indicating that both H-2 and non-H-2 genes may influence the elimination of this virus. Differences in virus spread prior to appearance of the immune response could not explain the observed differences in clearance rate. On the other hand, inefficient clearance always correlated with low T cell responsiveness measured in terms of virus-specific cytotoxicity and delayed-type hypersensitivity, whereas no correlation was found with regard to NK cell activity and antiviral antibody response. Analysis of F1 progeny between H-2 identical high and low responder strains showed that low responsiveness with regard to all three parameters was recessive, indicating that natural tolerance is not the mechanism explaining non-MHC dependent low responsiveness in this system. The implications of these findings are discussed with specific reference to the role of MHC genes in controlling resistance to infectious diseases.

Biochemical Characterization of Itchgrass (Rottboellia exaltata) Biotypes

Polyacrylamide electrophoresis and spectroscopic methods were used to characterize biotypes A and B itchgrass [Rottboellia exaltataL.f. # ROOEX] and their F2progeny. Electrophoretic analyses of F2progeny showed that differences between these two biotypes are multiallelic. Spectrophotometric data indicated differences between the photosynthetic apparatus of the two biotypes. These differences may reflect different abilities to adapt to varying light conditions and infer that these biotypes promote survival of the species by increasing the number of environmental nitches thatR. exaltatacan occupy.

Heritable variation in the phaseolin protein of nondomesticated common bean, Phaseolus vulgaris L.

Crude protein extracts from single seeds of nondomesticated Mexican bean accessions were analysed by SDS polyacrylamide gel electrophoresis for variability in phaseolin protein. Six new phaseolin types; 'M1', 'M2', 'M3', 'M4', 'M5', 'M6', which contained polypeptides within the same range of molecular weights (51,000 to 45,000 daltons) as occur in the 'S', 'T' and 'C' phaseolin types of cultivated beans were identified. No 'T' and 'C' types were found among the non-domesticated Mexican accessions, and the 'S' type occurred in less than 7% of the seeds screened. Genetic analyses of F2 progenies from crosses between 'Sanilac' ('S'), and five of the 'M' types showed that each 'M' phaseolin phenotype was allelic to the 'S' type and expressed codominantly.