Physiological epistasis, ontogenetic conflict and natural selection on physiology and life history

Ontogenetic conflict arises when optima for alleles governingfitness variation differ between juveniles and adults or betweenadult sexes. Loci that govern development of alternative phenotypesin the sexes, hereafter termed morph-determining loci, mediatedevelopment through the endocrine system. Morphotypic selectionis defined to be multivariate selection favoring discrete alternativemorphotypes (e.g., optima). When the optimal combinations ofalleles for alternative morphs differ between the sexes, itgenerates conflicting selection pressure and thus ontogeneticconflict. Selection on morph alleles promotes ontogenetic conflictbecause it perturbs physiological epistasis that governs theexpression of male versus female traits. Expression of physiologicaltraits arises from homeostasis that maintains trait expressionwithin a normal range. The genetic basis of homeostasis is likelyto arise from interactions among several genes (e.g., geneticepistasis) or protein products (e.g., physiological epistasis).For example, endocrine regulation arises from interactions betweengondatropins, which are protein hormones produced by the hypothalamic-pituitaryglands, and steroid hormones, which are produced by the gonads(e.g., HPG axis). The side-blotched lizard system is discussedwith respect to physiological bases of ontogenetic conflict.We also describe a novel molecular marker strategy for uncoveringgenome-wide physiological epistasis in nature. Finally, ontogeneticconflict exerts selection on females to evolve mate selectionor cryptic choice that is reflected in different sires beingchosen for son versus daughter production. We describe how side-blotchedlizard females ameliorate ontogenetic conflict by cryptic choiceof male genotypes to produce sons versus daughters.     

Vitrification, a complementary cryopreservation method for Betula pendula Roth

Cryopreservation--the storage of plant germplasm in liquid nitrogen--provides a modern tool for the conservation of forest genetic resources. It is especially applicable for species in which their micropropagation can be initiated from mature tree buds, e.g., silver birch (Betula pendula Roth), thus enabling the conservation of specific genotypes: endangered elite trees and trees expressing rare, valuable or interesting characteristics. The aim of the present study was to develop a vitrification protocol applicable for the cryostorage of silver birch that avoids the use of expensive sophisticated freezers. The average recovery of vitrified axillary silver birch buds was 71% using a protocol that started with four-week cold hardening of bud-bearing in vitro donor shoots on modified medium under short day conditions. After cold hardening, the excised axillary buds were precultivated on medium containing 0.7 M sucrose for 24 h under the same conditions as during the cold hardening period. Following preculture, the buds were treated with loading solution containing 2M glycerol and 0.4 M sucrose for 20 min at room temperature. Finally, the buds were dehydrated with PVS2 cryoprotectant for 120 min followed by direct immersion in liquid nitrogen. According to the morphology and the RAPD profiles of regenerated plants in the greenhouse, the genetic fidelity of the vitrified birch material seems to have remained unchanged.     

Variation in telomeric repeats of Scots pine (Pinus sylvestris L.)

The shortening of telomeres, the specific structures at the end of the eukaryotic chromosomes, has been associated with ageing and loss of cell replication or regeneration capacity. The aim of this study was to determine the variation in telomeric repeats during the life-span of Scots pine (Pinus sylvestris L.) by studying different tissues and age groups ranging from immature embryos to cambium, buds, and needles of mature, 200-year-old trees. The telomeric repeats in Scots pine including interstitial and centromeric repeats ranged from 0.9 up to 25 kb, and true telomeres were evaluated to have a mean length of 19.3 kb (±SE 0.17). Telomeres were observed to shorten with increasing tissue differentiation, embryonal samples having the longest repeats with an average length of 21.1 (±0.34) to 21.7 kb (±0.42) and the needles having, on average, the shortest repeats of 18.1 kb (±0.24). After germination, ageing per se had no significant effect on the length of telomeric repeats in cambium, bud, or needle tissues. In the older trees (50–200 years of age), the telomeres in stem cambium showed shortening towards the tree top. This is the first observation on such a position-related variation in telomeric repeats. Finally, there was a remarkable genotypic variation in the length of telomeric repeats, and this was consistent over the tissue types. In the small number of tested donor trees, the genotypic differences were not related to regeneration ability in tissue culture.     

Long Telomeres in Blood Leukocytes Are Associated with a High Risk of Ascending Aortic Aneurysm

Ascending aortic aneurysm is a connective tissue disorder. Even though multiple novel gene mutations have been identified, risk profiling and diagnosis before rupture still represent a challenge. There are studies demonstrating shorter telomere lengths in the blood leukocytes of abdominal aortic aneurysm patients. The aim of this study was to measure whether relative telomere lengths are changed in the blood leukocytes of ascending aortic aneurysm patients. We also studied the expression of telomerase in aortic tissue samples of ascending aortic aneurysms. Relative lengths of leukocyte telomeres were determined from blood samples of patients with ascending aortic aneurysms and compared with healthy controls. Telomerase expression, both at the level of mRNA and protein, was quantified from the aortic tissue samples. Mean relative telomere length was significantly longer in ascending aortic aneurysm blood samples compared with controls (T/S ratio 0.87 vs. 0.61, p<0.001). Expressions of telomerase mRNA and protein were elevated in the aortic aneurysm samples (p<0.05 and p<0.01). Our study reveals a significant difference in the mean length of blood leukocyte telomeres in ascending aortic aneurysm and controls. Furthermore, expression of telomerase, the main compensating factor for telomere loss, is elevated at both the mRNA and protein level in the samples of aneurysmal aorta. Further studies will be needed to confirm if this change in telomere length can serve as a tool for assessing the risk of ascending aortic aneurysm.     

Temperament clusters in a normal population: implications for health and disease

Background

The object of this study was to identify temperament patterns in the Finnish population, and to determine the relationship between these profiles and life habits, socioeconomic status, and health.

Methods/Principal Findings

A cluster analysis of the Temperament and Character Inventory subscales was performed on 3,761 individuals from the Northern Finland Birth Cohort 1966 and replicated on 2,097 individuals from the Cardiovascular Risk in Young Finns study. Clusters were formed using the k-means method and their relationship with 115 variables from the areas of life habits, socioeconomic status and health was examined.

Results

Four clusters were identified for both genders. Individuals from Cluster I are characterized by high persistence, low extravagance and disorderliness. They have healthy life habits, and lowest scores in most of the measures for psychiatric disorders. Cluster II individuals are characterized by low harm avoidance and high novelty seeking. They report the best physical capacity and highest level of income, but also high rate of divorce, smoking, and alcohol consumption. Individuals from Cluster III are not characterized by any extreme characteristic. Individuals from Cluster IV are characterized by high levels of harm avoidance, low levels of exploratory excitability and attachment, and score the lowest in most measures of health and well-being.

Conclusions

This study shows that the temperament subscales do not distribute randomly but have an endogenous structure, and that these patterns have strong associations to health, life events, and well-being.     

Thermal biology of genus Liolaemus: A phylogenetic approach reveals advantages of the genus to survive climate change

The trends of body temperatures in the field (T_b) and preferred body temperatures in the laboratory (T_pref) of the genus Liolaemus relative to reproductive mode, air temperature (T_air), precipitation, latitude, and elevation were studied using phylogenetic comparative analysis. Results were discussed in the framework of the evolution of thermal physiology and vulnerability to global climate change. Reproductive mode affects T_b but not T_pref. Whereas T_b and T_pref showed a significant association with T_air, there was no relationship with latitude or elevation.     

Correlational selection on lay date and life-history traits: experimental manipulations of territory and nest site quality

Abundant evidence suggests that females may engage in mate choice to gain nongenetic (material) benefits from high-quality territories; however, the selective consequences that influence those choices are not well understood. We studied the fitness effects of territory quality and incubation temperature on juvenile lizards in nature. We manipulated territory quality by redistributing rocks between pairs of neighboring home ranges. Rock manipulations set up adjacent plots that were either experimentally improved or reduced in quality. We incubated eggs from field-caught gravid females in each of three temperature treatments in the laboratory (low, medium, and high temperature). Progeny were released in either experimentally improved or reduced-quality plots upon hatching, and the following spring we measured survival as a function of egg size and laying date. We conducted concurrent studies of the thermal environment on experimental territories. Improved territories provided significantly more hours for lizards to behaviorally thermoregulate at their preferred body temperature and also provided nest sites with incubation conditions that were closer to optimal compared with reduced-quality plots. Reduced-quality plots were significantly more variable in quality. Finally, we measured significant correlational selection between egg mass and laying date on manipulated plots in two separate years. Results indicate the influence of environmental variation on correlational selection on life-history traits.     

Integrating ecophysiological models into species distribution projections of European reptile range shifts in response to climate change

Uncertainty in projections of global change impacts on biodiversity over the 21st century is high. Improved predictive accuracy is needed, highlighting the importance of using different types of models when predicting species range shifts. However, this is still rarely done. Our approach integrates the outputs of a spatially‐explicit physiologically inspired model of extinction and correlative species distribution models to assess climate‐change induced range shifts of three European reptile species (Lacerta lepida, Iberolacerta monticola, and Hemidactylus turcicus) in the coming decades. We integrated the two types of models by mapping and quantifying agreement and disagreement between their projections. We analyzed the relationships between climate change and projected range shifts. Agreement between model projections varied greatly between species and depended on whether or not they consider dispersal ability. Under our approach, the reliability of predictions is greatest where the predictions of these different types of models converge, and in this way uncertainty is reduced; sites where this convergence occurs are characterized by both current high temperatures and significant future temperature increase, suggesting they may become hotspots of local extinctions. Moreover, this approach can be readily implemented with other types of models.     

Exploring Causality between TV Viewing and Weight Change in Young and Middle-Aged Adults. The Cardiovascular Risk in Young Finns Study

Background

Television viewing time (TV time) is associated with increased weight and obesity, but it is unclear whether this relation is causal.

Methods and Results

We evaluated changes in TV time, waist circumference (waist) and body mass index (BMI) in participants of the population-based Cardiovascular Risk in Young Finns study (761 women, 626 men aged 33–50 years in 2011). Waist and BMI were measured, and TV time was self-reported in 2001, 2007, and 2011. Changes in waist and BMI between 2001 and 2011 were studied a) for the whole group, b) in groups with constantly low (≤1 h/d), moderate (1–3 h/d), or high (≥3 h/d) TV time, and c) in groups with ≥1 hour in-/decrease in daily TV time between 2001 and 2011. BMIs in 1986 were also evaluated. We explored the causal relationship of TV time with waist and BMI by classical temporality criterion and recently introduced causal-discovery algorithms (pairwise causality measures). Both methods supported the hypothesis that TV time is causative to weight gain, and no evidence was found for reverse or bidirectional causality. Constantly low TV time was associated with less pronounced increase in waist and BMI, and waist and BMI increase was lower with decreased TV time (P<0.05). The increase in waist and BMI was at least 2-fold in the high TV time group compared to the low TV time group (P<0.05). Adjustment for age, sex, BMI/waist in 2001, physical activity, energy intake, or smoking did not change the results.

Conclusions

In young and middle-aged adults, constantly high TV time is temporally antecedent to BMI and waist increase.     

Expression of Vitreoscilla haemoglobin in hybrid aspen (Populus tremula x tremuloides)

We describe the first ever expression of Vitreoscilla haemoglobin (VHb) in an economically important boreal woody plant hybrid aspen (Populus tremula x tremuloides). VHb has mainly been expressed in biotechnologically important unicellular organisms of both prokaryotic and eukaryotic origin. VHb expression, in this study, was analysed under different greenhouse cultivation conditions and under elevated UV-B illumination. Microscope analyses of leaves grown under optimized conditions revealed significant differences both in cell structure and size when the transgenic VHb lines were compared with the control lines. VHb lines displayed a higher relative volume of mitochondria and a significantly enhanced accumulation of starch in chloroplasts, all of which pointed towards changes in cellular energy production. Under elevated UV-B illumination, the differences between VHb lines became evident. Some specific VHb lines had elevated levels of total flavonoids, individual quercetin, kaempferol- and myricetin-derivatives relative to controls and other transgenic lines. This observation may reflect the availability of extra energy resources for secondary metabolite production and possibly an enhanced protection ability of these transgenic lines against UV-B illumination. Thus, all these findings point to changes in the energy metabolism of VHb lines. In the cultivation conditions tested this observation did not, however, result in a general improvement of elongation growth.