Silver birch telomeres shorten in tissue culture

Shortening of telomeres has been connected with ageing and loss of cell replication or regeneration capacity. The aim of the present study was to examine potential variation in the length of telomeric repeats in silver birch (Betula pendula Roth) using clonal materials consisting of different-aged outdoor trees and tissue cultures of seven genotypes. The overall average length of telomeres was 13.6 kb (±0.3), the minimum length of repeats in the different genotypes varied from 5.9 kb (±0.5) to 9.6 kb (±0.6), and the maximum length varied from 15.3 kb (±1.1) to 22.8 kb (±0.4). When germinated seeds and leaf and cambium samples from 15- and 80-year-old trees were compared, no correlation of ageing and the length of telomeric repeats was found. Positional variation in the telomere length was, however, observed in the cambium of mature trees, the stem base having longer repeats than the upper parts of the tree. Tissue cultures were found to have shorter telomeres than outdoor trees: prolonged culture, callus culture and stressful conditions were all observed to shorten telomeric repeats and should thus be avoided in birch micropropagation. There were significant differences among the studied silver birch genotypes in their telomere length, and these differences were consistent over the sample types. This is the first report on variation of telomeric repeats in a long-living organism studied with clonal materials.     

Temporal associations between daytime physical activity and sleep in children

Objectives

We examined temporal associations between objectively-measured physical activity (PA) during the day and in the evening, and sleep quantity and quality.

Study Design

PA and sleep were measured by actigraphs for an average of one week in an epidemiological cohort study of 275 eight-year-old children.

Results

For each one standard deviation (SD) unit of increased PA during the day, sleep duration was decreased by 0.30, sleep efficiency by 0.16, and sleep fragmentation increased by 0.08 SD units that night. For each one SD unit increase in sleep duration and efficiency the preceding night, PA the following day decreased by 0.09 and 0.16 SD units, respectively. When we contrasted days with a high amount of moderate to vigorous activity during the day or in the evening to days with a more sedentary profile, the results were essentially similar. However, moderate to vigorous PA in the evening shortened sleep latency.

Conclusions

The relationship between a higher level of PA and poorer sleep is bidirectional. These within-person findings challenge epidemiological findings showing that more active people report better sleep. Since only a few studies using objective measurements of both PA and sleep have been conducted in children, further studies are needed to confirm/refute these results.     

Long-term cryopreservation of Greek fir embryogenic cell lines: recovery, maturation and genetic fidelity

In coniferous species, including Greek fir (Abies cephalonica Loud), the involvement of somatic embryo plants in breeding and reforestation programs is dependent on the success of long-term cryostorage of embryogenic cultures during clonal field testing. In the present study on Greek fir, we assayed the recovery, morphological characteristics and genetic fidelity of embryogenic cell lines 6 and 8 during proliferation and maturation after long-term cryostorage. Our results indicate successful recovery of both cell lines after 6 years in cryostorage. In the maturation phase, both cell lines were capable of producing somatic embryos although some differences were detected among experiments. However, these changes were more dependent on the differences in the components of the maturation media or in the experimental set-up than on the long-term cryostorage. During both proliferation and maturation phases, the morphological fidelity of the embryogenic cultures as well as of the somatic embryos were alike before and after cryopreservation. The genetic fidelity of the cryopreserved cell line 6 that was assayed by random amplified polymorphic DNA (i.e. RAPD) markers demonstrated some changes in the RAPD profiles. The results indicate possible genetic aberrations caused by long-term cryopreservation or somaclonal variation during the proliferation stage. However, in spite of these changes the embryogenic cultures did not lose their proliferation or maturation abilities.     

Production of Norway spruce embryos in a temporary immersion system (TIS)

Somatic embryogenesis has already been used for Norway spruce (Picea abies (L.) Karst) embling production on a laboratory scale, but automation is needed to increase efficiency and reduce costs. One option to scale up production is mass production in bioreactors. In a series of experiments, a pro-embryogenic mass was propagated using Plantform temporary immersion system bioreactors, and the effect of different aeration cycles, support pad materials, and post-maturation treatments (rinsing and desiccation) on the embryo yield and embling survival after 4 to 6 mo in a greenhouse was tested. Three genotypes were used to test each treatment. The best aeration frequency was 20 min every 4 h, while a lower or higher frequency did not generally improve embryo production. Filter paper on plastic netting was the best support pad material in terms of usability and embryo production (varying from 177 ± 20 to 696 ± 109 per g pro-embryogenic mass). The separation of the embryos from the undeveloped cell mass by rinsing with sterile water resulted in reduced survival of the emblings. Desiccation treatment on nested plates with the embryos on the inner plate with or without filter paper improved their survival. Bioreactors were laborious to prepare, load, and clean. Improvements in embryo production can be achieved by optimizing the process, but bioreactors based on the requirements of somatic embryogenesis are needed to enable their use in the mass production of Norway spruce emblings.

     

The seasonal activity and the effect of mechanical bending and wounding on the PtCOMT promoter in Betula pendula Roth

In this study, 900-bp (signed as p including nucleotides –1 to –886) and partly deleted (signed as dp including nucleotides –1 to –414) COMT (caffeate/5-hydroxyferulate O-methyltransferase) promoters from Populus tremuloides Michx. were fused to the GUS reporter gene, and the tissue-specific expression patterns of the promoters were determined in Betula pendula Roth along the growing season, and as a response to mechanical bending and wounding. The main activity of the PtCOMTp- and PtCOMTdp-promoters, determined by the histochemical GUS assay, was found in the developing xylem of stems during the 8th–13th week and in the developing xylem of roots in the 13th week of the growing season. The GUS expression patterns did not differ among the xylem cell types. The PtCOMT promoter-induced GUS expression observed in phloem fibres suggests a need for PtCOMT expression and thus syringyl (S) lignin synthesis in fibre lignification. However, the PtCOMTdp-promoter induced GUS expression in stem trichomes, which may contribute to the biosynthesis of phenylpropanoid pathway-derived compounds other than lignin. Finally, a strong GUS expression was induced by the PtCOMT promoters in response to mechanical stem bending but not to wounding. The lack of major differences between the PtCOMTp- and PtCOMTdp-promoters suggests that the deleted promoter sequence (including nucleotides −415 to −886) did not contain a significant regulatory element contributing to the GUS expression in young B. pendula trees.     

Heritable body size mediates apparent life-history trade-offs in a simultaneous hermaphrodite

Physiological trade-offs between life-history traits can constrain natural selection and maintain genetic variation in the face of selection, thereby shaping evolutionary trajectories. This study examines physiological trade-offs in simultaneously hermaphroditic banana slugs, Ariolimax dolichophallus. These slugs have high heritable variation in body size, which strongly predicts the number of clutches laid, hatching success and progeny growth rate. These fitness components were associated, but only when examined in correlation with body size. Body size mediated these apparent trade-offs in a continuum where small animals produced rapidly growing progeny, intermediate-sized animals laid many clutches and large animals had high hatching success. This study uses a novel statistical method in which the components of fitness are analysed in a mancova and related to a common covariate, body size, which has high heritability. The mancova reveals physiological trade-offs among the components of fitness that were previously masked by high variation in body size.     

Discrete genetic variation in mate choice and a condition-dependent preference function in the side-blotched lizard: implications for the formation and maintenance of coadapted gene complexes

Variation in female preference functions, both genotypic andphenotypic, has been largely ignored in the literature, despiteits implications to the maintenance of genetic variation inpopulations and the resolution of the "Lek paradox." Polymorphicpopulations, such as in the side-blotched lizard, provide idealstudy systems for its investigation, especially in the contextof incipient processes of sympatric speciation. Females of theside blotch lizard exist in 2 genetically distinct morphs, yellowthroated and orange throated, that experience disruptive selectionfor life history traits. Males express 3 throat color morphs,blue, orange, and yellow, that exhibit alternative strategiesin intrasexual competition. We experimentally tested for femalepreference in triadic mate choice trials to identify the presenceof discrete genetic and condition-dependent variation in femalepreference function. We found that females did in fact showgenetic variation in preference for males but that females alsooperate a multicondition preference function dependent uponthe genotype of the female and her state (number of clutcheslaid). Females exhibited positive assortative mating prior tothe first clutch. However, prior to later clutches, orange femalesswitched choice, preferring yellow males. These findings arediscussed in relation to the maintenance of coadapted gene complexeswithin populations and the prevention of divergent directionalselection (population bifurcation) by condition-dependent variationin mate choice.     

Direct fitness correlates and thermal consequences of facultative aggregation in a desert lizard

Social aggregation is a common behavioral phenomenon thought to evolve through adaptive benefits to group living. Comparing fitness differences between aggregated and solitary individuals in nature - necessary to infer an evolutionary benefit to living in groups - has proven difficult because communally-living species tend to be obligately social and behaviorally complex. However, these differences and the mechanisms driving them are critical to understanding how solitary individuals transition to group living, as well as how and why nascent social systems change over time. Here we demonstrate that facultative aggregation in a reptile (the Desert Night Lizard, Xantusia vigilis) confers direct reproductive success and survival advantages and that thermal benefits of winter huddling disproportionately benefit small juveniles, which can favor delayed dispersal of offspring and the formation of kin groups. Using climate projection models, however, we estimate that future aggregation in night lizards could decline more than 50% due to warmer temperatures. Our results support the theory that transitions to group living arise from direct benefits to social individuals and offer a clear mechanism for the origin of kin groups through juvenile philopatry. The temperature dependence of aggregation in this and other taxa suggests that environmental variation may be a powerful but underappreciated force in the rapid transition between social and solitary behavior.     

Mycobacterium tuberculosis Strains Potentially Involved in the TB Epidemic in Sweden a Century Ago

A hundred years ago the prevalence of tuberculosis (TB) in Sweden was one of the highest in the world. In this study we conducted a population-based search for distinct strains of Mycobacterium tuberculosis complex isolated from patients born in Sweden before 1945. Many of these isolates represent the M. tuberculosis complex population that fueled the TB epidemic in Sweden during the first half of the 20^th century.

Methods

Genetic relationships between strains that caused the epidemic and present day strains were studied by spoligotyping and restriction fragment length polymorphism.

Results

The majority of the isolates from the elderly population were evolutionary recent Principal Genetic Group (PGG)2/3 strains (363/409 or 88.8%), and only a low proportion were ancient PGG1 strains (24/409 or 5.9%). Twenty-two were undefined. The isolates demonstrated a population where the Euro-American superlineage dominated; in particular with Haarlem (41.1%) and T (37.7%) spoligotypes and only 21.2% belonged to other spoligotype families. Isolates from the elderly population clustered much less frequently than did isolates from a young control group population.

Conclusions

A closely knit pool of PGG2/3 strains restricted to Sweden and its immediate neighbours appears to have played a role in the epidemic, while PGG1 strains are usually linked to migrants in todaýs Sweden. Further studies of these outbreak strains may give indications of why the epidemic waned.