Non-random inheritance of organellar genomes in symmetric and asymmetric somatic hybrids between Lycopersicon esculentum and L. pennellii

Summary The organization of the mitochondrial genome and the genotype of the chloroplast genome was characterized using restriction fragment length polymorphisms in a population (82 individuals) of symmetric and asymmetric somatic hybrids of tomato. The protoplast fusion products were regenerated following the fusion of leaf mesophyll protoplasts of Lycopersicon esculentum (tomato cv UC82) with suspension cell protoplasts of L. pennellii that had been irradiated with 5, 10, 15, 25, 50, or 100 kRads from a gamma source. The chloroplast genome in the somatic hybrids showed a random pattern of inheritance, i.e., either parental genome was present in equal numbers of regenerants, while in asymmetric somatic hybrids, the chloroplast genotype reflected the predominant nuclear genotype, i.e., tomato. The mitochondrial genome in the symmetric somatic hybrids showed a non-random pattern of inheritance, i.e., predominantly from the L. pennellii parent; asymmetric somatic hybrids had more tomato-specific mitochondrial sequences than symmetric somatic hybrids. The non-random inheritance of the chloroplast and mitochondrial DNA in these tomato protoplast fusion products appears to be influenced by the nuclear background of the regenerant.     

When dispersal fails: unexpected genetic separation in Gibraltar macaques (Macaca sylvanus)

Barbary macaques (Macaca sylvanus), now restricted in the wild to a few isolated forested areas of Morocco and Algeria, are present in a free‐ranging colony on Gibraltar. For many decades, the Gibraltar colony was exposed to multiple bottlenecks due to highly nonrandom removal of animals, followed by repeated introductions of animals from North Africa. Moreover, because of complete isolation, Gibraltar's several social groups of macaques provide an ideal system to study the genetic consequences of dispersal in cercopithecines in situ. Predictions of genetic consequences due to male‐biased dispersal in cercopithecines will be different for autosomal and maternally inherited genetic markers, such as the control region of the mitochondrial DNA. We used a panel of 14 highly polymorphic microsatellite loci and part of the hypervariable region I of the mitochondrial control region to estimate genetic structure between five social groups in Gibraltar. Surprisingly, for autosomal markers, both classical summary statistics and an individual‐based method using a Bayesian framework detected significant genetic structure between social groups in Gibraltar, despite much closer proximity than wild Algerian and Moroccan populations. Mitochondrial data support this finding, as a very substantial portion of the total genetic variation (70.2%) was found between social groups. Using two Bayesian approaches, we likewise identified not only a small number of male first‐generation immigrants (albeit less than expected for cercopithecines) but also unexpectedly a few females. We hypothesize that the culling of males that are more likely to disperse might slow down genetic homogenization among neighbouring groups, but may also and more perversely produce selection on certain behavioural traits. This may have important repercussions for conservation, as it could lead to evolutionary changes that are not due to inbreeding or genetic drift.     

Osteogenesis imperfecta: the audiological phenotype lacks correlation with the genotype

Background

Neurofibromatosis 1 (NF1), a common autosomal dominant disorder, was shown in one study to be associated with a 15-year decrease in life expectancy. However, data on mortality in NF1 are limited. Our aim was to evaluate mortality in a large retrospective cohort of NF1 patients seen in France between 1980 and 2006.

Methods

Consecutive NF1 patients referred to the National French Referral Center for Neurofibromatoses were included. The standardized mortality ratio (SMR) with its 95% confidence interval (CI) was calculated as the ratio of observed over expected numbers of deaths. We studied factors associated with death and causes of death.

Results

Between 1980 and 2006, 1895 NF1 patients were seen. Median follow-up was 6.8 years (range, 0.4-20.6). Vital status was available for 1226 (65%) patients, of whom 1159 (94.5%) survived and 67 (5.5%) died. Overall mortality was significantly increased in the NF1 cohort (SMR, 2.02; CI, 1.6-2.6; P < 10^-4). The excess mortality occurred among patients aged 10 to 20 years (SMR, 5.2; CI, 2.6-9.3; P < 10^-4) and 20 to 40 years (SMR, 4.1; 2.8-5.8; P < 10^-4). Significant excess mortality was found in both males and females. In the 10-20 year age group, females had a significant increase in mortality compared to males (SMR, 12.6; CI, 5.7-23.9; and SMR, 1.8; CI, 0.2-6.4; respectively). The cause of death was available for 58 (86.6%) patients; malignant nerve sheath tumor was the main cause of death (60%).

Conclusions

We found significantly increased SMRs indicating excess mortality in NF1 patients compared to the general population. The definitive diagnosis of NF1 in all patients is a strength of our study, and the high rate of death related to malignant transformation is consistent with previous work. The retrospective design and hospital-based recruitment are limitations of our study. Mortality was significantly increased in NF1 patients aged 10 to 40 years and tended to be higher in females than in males.     

Tomato chromosome 1: high resolution genetic and physical mapping of the short arm in an interspecific Lycopersicon esculentum × L. peruvianum cross

 A detailed map of part of the short arm of chromosome 1 proximal to the Cf-4/Cf-9 gene cluster was generated by using an F₂ population of 314 plants obtained from the cross between the remotely related species Lycopersicon esculentum and L. peruvianum. Six markers that cosegregate in an L. esculentum×L. pennellii F₂ population showed high recombination frequencies in the present interspecific population, spanning an interval of approximately 13 cM. Physical distances between RFLP markers were estimated by pulsed field gel electrophoresis of high-molecular-weight DNA and by identifying YACs that recognized more than one RFLP marker. In this region 1 cM corresponded to 55–110 kb. In comparsion with the value of 730 kb per cM averaged over the entire genome, this reflects the remarkably high recombination frequencies in this region in the hybrid L. esculentum×L. peruvianum progeny population. The present data underline the fact that recombination is not a process that occurs randomly over the entire genome, but can vary dramatically in intensity between chromosomal regions and among populations. Received: 20 May 1996 / Accepted: 10 September 1996     

Morphology,Carbohydrate Composition and Vernalization Response in a Genetically Diverse Collection of Asian and European Turnips (Brassica rapa subsp. rapa)

Brassica rapa displays enormous morphological diversity, with leafy vegetables, turnips and oil crops. Turnips (Brassica rapa subsp. rapa) represent one of the morphotypes, which form tubers and can be used to study the genetics underlying storage organ formation. In the present study we investigated several characteristics of an extensive turnip collection comprising 56 accessions from both Asia (mainly Japanese origin) and Europe. Population structure was calculated using data from 280 evenly distributed SNP markers over 56 turnip accessions. We studied the anatomy of turnip tubers and measured carbohydrate composition of the mature turnip tubers of a subset of the collection. The variation in 16 leaf traits, 12 tuber traits and flowering time was evaluated in five independent experiments for the entire collection. The effect of vernalization on flowering and tuber formation was also investigated. SNP marker profiling basically divided the turnip accessions into two subpopulations, with admixture, generally corresponding with geographical origin (Europe or Asia). The enlarged turnip tuber consists of both hypocotyl and root tissue, but the proportion of the two tissues differs between accessions. The ratio of sucrose to fructose and glucose differed among accessions, while generally starch content was low. The evaluated traits segregated in both subpopulations, with leaf shape, tuber colour and number of shoots per tuber explaining most variation between the two subpopulations. Vernalization resulted in reduced flowering time and smaller tubers for the Asian turnips whereas the European turnips were less affected by vernalization.     

Design and implementation of a qualitative simulation model of lambda phage infection

MOTIVATION: Molecular biology databases hold a large number of empirical facts about many different aspects of biological entities. That data is static in the sense that one cannot ask a database 'What effect has protein A on gene B?' or 'Do gene A and gene B interact, and if so, how?'. Those questions require an explicit model of the target organism. Traditionally, biochemical systems are modelled using kinetics and differential equations in a quantitative simulator. For many biological processes however, detailed quantitative information is not available, only qualitative or fuzzy statements about the nature of interactions. RESULTS: We designed and implemented a qualitative simulation model of lambda phage growth control in Escherichia coli based on the existing simulation environment QSim. Qualitative reasoning can serve as the basis for automatic transformation of contents of genomic databases into interactive modelling systems that can reason about the relations and interactions of biological entities.      

Inhibitory effects of some esters of 2- and 3-substituted alkoxyphenylcarbamic acids on photosynthetic characteristics

The inhibitory effect of 23N-alkyl-4-piperidylesters (alkyl = ethyl-butyl) (APEA) and 8N-ethyl-2-pyrrolidinylmethylesters (EPMEA) of 2- and 3-substituted alkoxyphenylcarbamic acids (alkoxy = butoxy-heptyloxy-) on photosynthetic Hill reaction activity of spinach chloroplasts and on chlorophyll (Chl) synthesis in green algaeChlorella vulgaris was investigated. Inhibitory activities of these compounds were strongly connected with the lipophilicity of the whole molecule. A lower inhibitory activity of 2-alkoxy-substituted derivatives in relation to the corresponding 3-substituted ones was confirmed. Electron spin resonance (ESR) spectra of spinach chloroplasts demonstrated that the studied compounds affected the structure of photosystem (PS) 2 with the release of Mn²⁺ ions into interior of thylakoid membranes.     

Quantitative trait loci analysis of phytate and phosphate concentrations in seeds and leaves of Brassica rapa

Phytate, being the major storage form of phosphorus in plants, is considered to be an anti-nutritional substance for human, because of its ability to complex essential micronutrients. In the present study, we describe the genetic analysis of phytate and phosphate concentrations in Brassica rapa using five segregating populations, involving eight parental accessions representing different cultivar groups. A total of 25 quantitative trait loci (QTL) affecting phytate and phosphate concentrations in seeds and leaves were detected, most of them located in linkage groups R01, R03, R06 and R07. Two QTL affecting seed phytate (SPHY), two QTL affecting seed phosphate (SPHO), one QTL affecting leaf phosphate and one major QTL affecting leaf phytate (LPHY) were detected in at least two populations. Co-localization of QTL suggested single or linked loci to be involved in the accumulation of phytate or phosphate in seeds or leaves. Some co-localizing QTL for SPHY and SPHO had parental alleles with effects in the same direction suggesting that they control the total phosphorus concentration. For other QTL, the allelic effect was opposite for phosphate and phytate, suggesting that these QTL are specific for the phytate pathway.     

Hyaluronic acid of high molecular weight inhibits proliferation and induces cell death in U937 macrophage cells

Hyaluronic acid (HA), a major glycosaminoglycan component of the extracellular matrix, has regulatory influences on cells and cellular activities. To explore the effects of a high concentration (1 mg/mL) of high molecular weight HA (500-730 kD) on U937 macrophage growth dynamics, three factors that influence overall cellular growth, namely proliferation, apoptosis, and cell death, were examined. Cells were cultured with HA and were analyzed by flow cytometry every 24 hours during a 168-hour period for proliferation and the presence of apoptotic and dead cells. These analyses demonstrated that HA inhibits U937 macrophage proliferation in a time-dependent manner. Through the first 72 hours, cells exhibited slowed proliferation. However, no evidence of cell division arrest or reduced cell viability was observed. Thereafter, HA continued to diminish proliferation, but induced apoptosis. This data is consistent with regulatory influences secondary to HA binding to CD44 and/or RHAMM cell surface receptors, both of which were shown to be expressed on U937 macrophages. This study demonstrates that a high concentration of high molecular weight HA greatly inhibits macrophage population growth by the dual actions of impeding cell proliferation and inducing apoptosis.