Does DNA methylation pattern mark generative development in winter rape?

In this paper we report on changes in DNA methylation pattern in rape apices and leaves during transition from vegetative to reproductive stage due to grafting and/or vernalization. Grafted plants of winter rape (Brassica napus L., var. "Górczański") (stock from vernalized, scion from non-vernalized plants) were used together with vernalized non-grafted plants. In addition, methylation status was determined also in spring rape (var. "M?ochowski") grown under normal and low temperature. The methylation-sensitive amplification polymorphism (MSAP) method with EcoRI/MspI and EcoRII/HpaII restriction enzymes was employed. The majority (ca. 68%) of analyzed loci (566 in winter and 551 in spring rape) were monomorphic, i.e. did not undergo methylation. Both cultivars showed a similar degree of methylation. 188 loci in winter and 176 in spring cultivars expressed changes in the methylation pattern. All differentially amplified fragments resulted from either full methylation of an internal cytosine or from hemi-methylation of an external cytosine. A pair-wise comparison showed that a similar number of loci underwent development-related methylation changes in apices of the winter and spring rape. The majority (80%) of changes were demethylation events in generative (vernalized) apices of the winter cultivar. However, an increased number of demethylated loci was detected in vernalized apices in comparison with generative, non-vernalized ones. In apices of vegetative and generative grafted plants the same number of demethylation events was observed. Overall, 10 MSAP loci were detected that expressed methylation changes in vernalized apices only; among them 7 loci underwent demethylation after vernalization and remained methylated in both vegetative and generative non-vernalized stage. Only 1 locus was demethylated in generative non-vernalized apices. Thus, most of demethylation events can be ascribed to vernalization and not to the generative stage. In leaves of winter rape methylation and demethylation events occurred with similar frequency, while in the spring cultivar more demethylation events were detected. The results show that during vernalization and transition to the generative stage different sets of genes are activated.     

β-Oxidation enzymes in the mitochondria of Arum and oilseed rape

-Oxidation enzymes were detected both in the mitochondria and microbodies of Arum maculatum L. spadices and Brassica napus L. seeds. It is apparent that the mitochondrial membrane barrier, which remains intact after sucrose-density-gradient centrifugation, prevents rapid access of acyl-GoA substrates to matrix oxidation tes. Thus intact mitochondria showed little -oxidation enzyme activity. Rupturing of the mitochondrial membrane allowed rapid access of acyl CoAs to matrix sites. Consequently, in ruptured mitochondria, high -oxidation enzyme activities were measured.C. Masterson thanks the Science and Engineering Research Council for the award of a postgraduate student maintenance grant. D.R. Thomas and C. Wood thank their relatives for continuing financial support. The authors also thank West Cumberland Farmers Ltd., Hexham, UK for their gift of oilseed rape seeds.     

Is hypothermia necessary for the winter survival of the GoldcrestRegulus regulus?

Summary The Goldcrest is an interesting species for studies of physiological and behavioural adaptions to cold, since it is the smallest species present in Europe. Although many small birds have to lower their metabolic rate and enter hypothermia in order to make their energy reserves last throughout the night, our measurements of oxygen consumption of five Goldcrests suggest that these birds may be able to balance their nocturnal energy budget during the winter at normothermic body temperatures, provided that the available food supply is adequate. These results are in agreement with those of another small bird, the Common Bushtit, which, like the Goldcrest, reduce nocturnal heat loss by contact roosting. Since the energy saved by hypothermia decreases with decreasing ambient temperature and also decreasing body weight, this strategy might not be such an advantage for the smallest birds living at very low ambient temperatures.

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Zusammenfassung Am Wintergoldhähnchen als dem kleinsten europäischen Vogel interessieren besonders seine physiologischen und Verhaltens-Anpassungen an niedere Temperaturen. Viele Kleinvögel senken ihre Stoffwechselaktivität und verfallen in Hypothermie, um mit ihren Energie-Reserven während der langen Winternächte auszukommen. Unsere Untersuchungen über den O₂-Verbrauch von 5 Wintergoldhähnchen legen jedoch nahe, daß sich das nächtliche Energie-Budget auch im Tiefwinter auf Normalniveau bewegt und daß sie bei ausreichendem Nahrungsangebot ihre normale Körpertemperatur auch nachts beibehalten. Ähnliche Befunde liegen von den vergleichbaren kleinen amerikanischen Buschmeisen vor, die wie Goldhähnchen den nächtlichen Wärmeverlust durch Schlafen auf engem Gefiederkontakt reduzieren. Es ist anzunehmen, daß die Hypothermie als Überwinterungsstrategie für unsere kleinsten Vögel garnicht so vorteilhaft wäre: Die durch Hypothermie eingesparte Energie geht mit abnehmender Umgebungstemperatur und mit geringerer Körpergröße wieder verloren.

     

Does human scent bias the survival of bird nests?

Human-scent contamination of bird nests and the human-made trails leading to them is suspected to influence nest survival by attracting or deterring predatory mammals. This paper (1) reviews studies in which human-scent contamination was suspected to have biased the survival of real and artificial nests by influencing the behaviour of predatory mammals, (2) summarizes the procedures used in attempts to mitigate human-scent contamination in nest-survival studies, and (3) describes procedures to enhance the design and interpretation of nest-survival experiments. The behaviour of various non-domesticated mammals is confirmed or suspected to be affected by human scent, so similar effects on nest predators are plausible. However, suggestions that human scent affects nest survival by influencing the behaviour of predatory mammals are poorly supported, due to a dearth of appropriately designed experiments. Some studies failed to include measures to reduce human-scent contamination, and the effectiveness of scent-mitigation methods used in other studies has seldom been verified. In addition, volatile compounds arising from soil and vegetation disturbed underfoot by field researchers may have confounded many nest-survival studies. Investigators have routinely inferred human-scent effects from post hoc predation patterns or have simply acknowledged possible human-scent effects among other potential influences of nest fate. Studies are needed of the effects of human scent using uniform methods of scent application and verified methods of scent mitigation, where the fates of different types of nests are examined under a range of field conditions. More fundamentally, studies of naïve and experienced mammals are needed to assess their responses to human scent and clarify its salience in wildlife disturbance.     

Does the use of DM-nitrophen,nitr-5, or diazo-2 interfere with the measurement of indo-1 fluorescence?

Emission spectra of the photolabile Ca2+ chelators DM-nitrophen, nitr-5, and diazo-2 were studied alone, and in the presence of indo-1, to investigate potential interactions that would make the simultaneous manipulation and ratiometric measurement of the intracellular Ca2+ concentration difficult. Neither diazo-2 nor its photoproduct were found to be significantly fluorescent, and consequently concentrations of diazo-2 up to 20 times that of indo-1 did not distort the emission spectra of indo-1. DM-nitrophen was scarcely fluorescent, but its fluorescence did increase upon photolysis. In contrast to diazo-2 and DM-nitrophen, nitr-5 itself was found to be quite fluorescent, and this fluorescence was significantly increased upon photolysis. Thus, combined use of nitr-5 and indo-1 poses the most difficulty. The emission spectra of all the investigated compounds were used to define experimental conditions and calibration procedures that make possible simultaneous measurement and manipulation of the intracellular Ca2+ concentration.     

Does the lack of root hairs alter root system architecture of Zea mays?

Plant and Soil - Root hairs are one root trait among many which enables plants to adapt to environmental conditions. How different traits are coordinated and whether some are mutually exclusive is...     

Does maternal stress influence winter survival of offspring in root voles Microtus oeconomus? A field experiment

Maternal stress can have long‐term adverse consequences on immunocompetence and disease risk of offspring, and winter survival is a crucial demographic parameter in the life‐history of an individual that can substantially affect northern rodent population dynamics. An understanding of the effects of maternal stress on winter survival of offspring may help identify mechanisms driving population fluctuations of northern small mammals. Thus, we assessed the effects of maternal stress, resulting from high population densities, on winter survival of first generation (F₁) and second generation (F₂) in root voles Microtus oeconomus. Replicate high‐ and low‐density enclosed parental populations were established, from which we obtained F₁ generation that were used to establish new enclosed, equal‐density populations. The adults of the high‐density parental populations had higher corticosterone levels, an indication of physiological stress, than did those of the low‐density parental populations. Over‐winter survival of the F₁ generation voles from the low‐density parental populations was greater than that of those from the high‐density parental populations. Over‐winter survival of F₂ generation voles did not differ between the two treatments. Our results suggest that maternal stress affected over‐winter survival of first generations but not second generations. Reduced immunocompetence, resulting from high population density stresses, transferred to offspring may be a factor in annual (winter) population declines. Because the effect is transitory, i.e. immunocompetence of F₂ voles is not affected, reduced immunocompetence resulting from high density stresses would not contribute to lengthy periods of low population densities that are characteristic of multi‐annual population fluctuations.     

Does climate change influence the availability and quality of reindeer forage plants?

The northward and upward movement of the tree line and gradual replacement of lichens with vascular plants associated with increasing temperatures and nutrient availability may change the reindeer pastures in Northern Fennoscandia. The productivity of reindeer forage will most probably increase, but their protein (nitrogen) concentrations may decrease because of higher temperatures and CO₂ concentration. In the long term, the nutritive value of forage will depend on the mineralization rate and nutrient uptake from the soil. Enhanced UV-B is likely to increase the concentration of phenolics, decreasing forage quality and choice, but reindeer may adapt to increased phenolics. Increased winter precipitation, the occurrence of ice layers, deeper snow cover, and the appearance of molds beneath the snow cover may reduce the availability and/or quality of reindeer forage, but prolongation of snowless periods might have the opposite effect. The net balance of negative and positive effects will vary regionally depending on the climate, bedrock, vegetation, reindeer herding systems and socio-political factors. Multidisciplinary research is needed most importantly on the effects of the changing winter climate on reindeer forage, and the effect of modified forage quality on reindeer physiology.

Does lack of available suitable habitat explain the patchy distributions of rare calcicole fern species?

In Canada, as in many countries, a relatively large number of fern species occur in specialized habitats and have low numbers of known populations containing few individuals. It has been suggested that the distribution of ferns is mostly determined by factors of climate and habitat due to relatively low limitations in ferns for dispersal and establishment. Here, we attempt to explain whether the local patchy distribution of three calcicole fern species rare in Canada ( Asplenium ruta-muraria , Pellaea atropurpurea and Woodsia obtusa ) is due to a lack of available habitat. Analyses based on micro-scale differences between sites occupied by the ferns and nearby, unoccupied sites did not reveal any significant differences, thereby indicating that the rarity of these species is not entirely driven by the rarity of their microhabitat at a local scale. Our results suggest that the widely accepted premise that ferns are not limited by dispersal or establishment should be reconsidered, as such limitations are the only likely explanation for empty available and suitable habitat.     

Does colour polymorphism enhance survival of prey populations?

That colour polymorphism may protect prey populations from predation is an old but rarely tested hypothesis. We examine whether colour polymorphic populations of prey exposed to avian predators in an ecologically valid visual context were exposed to increased extinction risk compared with monomorphic populations. We made 2976 artificial pastry prey, resembling Lepidoptera larvae, in four different colours and presented them in 124 monomorphic and 124 tetramorphic populations on tree trunks and branches such that they would be exposed to predation by free-living birds, and monitored their ‘survival’. Among monomorphic populations, there was a significant effect of prey coloration on survival, confirming that coloration influenced susceptibility to visually oriented predators. Survival of polymorphic populations was inferior to that of monomorphic green populations, but did not differ significantly from monomorphic brown, yellow or red populations. Differences in survival within polymorphic populations paralleled those seen among monomorphic populations; the red morph most frequently went extinct first and the green morph most frequently survived the longest. Our findings do not support the traditional protective polymorphism hypothesis and are in conflict with those of earlier studies. As a possible explanation to our findings, we offer a competing ‘giveaway cue’ hypothesis: that polymorphic populations may include one morph that attracts the attention of predators and that polymorphic populations therefore may suffer increased predation compared with some monomorphic populations.     

Does lemming winter grazing impact vegetation in the Canadian Arctic?

In low-productivity environments such as the tundra, it has been proposed that regular, multi-annual population cycles of lemmings could be driven by winter food depletion in years of peak abundance. If lemming population dynamics is controlled by food resources, we predict that (1) winter grazing should negatively impact the abundance of food plants, (2) this impact should be proportional to lemming density and (3) high lemming winter grazing pressure should result in reduced plant growth during the following summer. We tested these predictions on Bylot Island, Nunavut, Canada, where two species of lemmings are present: the brown (Lemmus trimucronatus) and collared lemming (Dicrostonyx groenlandicus). We installed 16 exclosures in their preferred wintering habitat (snowbeds) and annually sampled plant biomass inside and outside exclosures at snow melt and at peak growth during the summers of 2009–2012, covering a full population cycle. Winter grazing had no impact on total vascular plant or moss biomass at snow melt in all years. Among plant families, only Caryophyllaceae, which was uncommon, showed a decline. In moss taxa, a negative effect was found on Polytrichum in only 1 year out of three. Overall, plant regrowth during the subsequent summer showed annual variation and tended to be reduced in the 2 years of high lemming abundance. However, this could be a consequence of summer grazing. Overall, the impact of lemming winter grazing on plants was weak and short-lived, even in years of high lemming abundance. Therefore, our results are not consistent with the hypothesis that food depletion during winter was the cause of the lemming decline following peak abundance at our study site. Other factors may limit lemming populations and prevent them from reaching densities high enough to exhaust their food resources.     

IS male-sterility in plants related to lack of cyanide-resistant respiration in tissues?

Cyanide-resistant (alternative) respiration by tissues of 7 male-sterile lines from 4 species (Glycine max (L.), Helenium amarum (Raf.) H. Rock., Plantago lanceolata L. and Zea mays L.) was compared with that of fertile tissues. Six of the 7 male-sterile lines lacked alternative respiration in the tissue assayed (leaf or root), while the corresponding fertile tissue displayed a typical alternative pathway equivalent to about 20% of the uninhibited respiratory rate. The exception to this pattern was the male-sterile maize line cytoplasmic male sterile (cms)-T, which had an alternative pathway equivalent to that of the fertile line. Mitochondria isolated from male-sterile cms-C maize were found to have an alternative pathway, but the capacity of this pathway was only one-half to two-thirds as large as that found in mitochondria from the male-fertile N line. Thus while no alternative pathway could be detected in intact cms-C tissue, it was found in the isolated mitochondria, suggesting that the pathway is somehow suppressed in the intact tissue. Since cytokinins are known to both inhibit the alternative pathway and affect floral development, they represent potential candidates for the suppressing agent involved. The lack of alternative respiration in the male-sterile lines might also serve to explain the commonly observed higher productivity and vigor of male-sterile plants compared to fertile ones.     

Interactions of elevated carbon dioxide and temperature with aphid feeding on transgenic oilseed rape: Are Bacillus thuringiensis (Bt) plants more susceptible to nontarget herbivores in future climate?

Climate change factors such as elevated carbon dioxide (CO₂) and temperature typically affect carbon (C) and nitrogen (N) dynamics of crop plants and the performance of insect herbivores. Insect‐resistant transgenic plants invest some nutrients to the production of specific toxic proteins [i.e. endotoxins from Bacillus thuringiensis (Bt)], which could alter the C–N balance of these plants, especially under changed abiotic conditions. Aphids are nonsusceptible to Lepidoptera‐targeted Bt Cry1Ac toxin and they typically show response to abiotic conditions, and here we sought to discover whether they might perform differently on compositionally changed Bt oilseed rape. Bt oilseed rape had increased N content in the leaves coupled with reduced total C compared with its nontransgenic counterpart, but in general the C : N responses of both plant types to elevated CO₂ and temperature were similar. Elevated CO₂ decreased N content and increased C : N ratio of both plant types. Elevated temperature increased C and N contents, total chlorophyll and carotenoid concentrations under ambient CO₂, but decreased these under elevated CO₂. In addition, soluble sugars were increased and starch decreased by elevated temperature under ambient but not under elevated CO₂, whereas photosynthesis was decreased in plants grown under elevated temperature in both CO₂ levels. Myzus persicae, a generalist aphid species, responded directly to elevated temperature with reduced developmental time and decreased adult and progeny weights, whereas the development of the Brassica specialist Brevicoryne brassicae was less affected. Feeding by M. persicae resulted in an increase in the N content of oilseed rape leaves under ambient CO₂, indicating the potential of herbivore feeding itself to cause allocation changes. The aphids performed equally well on both plant types despite the differences between C–N ratios of Bt and non‐Bt oilseed rape, revealing the absence of plant composition‐related effects on these pests under elevated CO₂, elevated temperature or combined elevated CO₂ and temperature conditions.     

Does water stress promote the proteome-wide adjustment of intrinsically disordered proteins in plants?

Plant response to water stress involves the activation of mechanisms expected to help them cope with water scarcity. Among these mechanisms, proteome-wide adjustment is well known. This includes actions to save energy, protect cellular and molecular components, and maintain vital functions of the cell. Intrinsically disordered proteins, which are proteins without a rigid three-dimensional structure, are seen as emerging multifunctional cellular components of proteomes. They are highly abundant in eukaryotic proteomes, and numerous functions for these proteins have been proposed. Here, we discuss several reasons why the collection of intrinsically disordered proteins in a proteome (disordome) could be subjected to an active regulation during conditions of water scarcity in plants. We also discuss the potential misinterpretations of disordome content estimations made so far due to bias-prone data and the need for reliable analysis based on experimental data in order to acknowledge the plasticity nature of the disordome.     

Nonlinear effects of winter sea ice on the survival probabilities of Adélie penguins

The population dynamics of Antarctic seabirds are influenced by variations in winter sea ice extent and persistence; however, the type of relationship differs according to the region and the demographic parameter considered. We used annual presence/absence data obtained from 1,138 individually marked birds to study the influence of environmental and individual characteristics on the survival of Adélie penguins Pygoscelis adeliae at Edmonson Point (Ross Sea, Antarctica) between 1994 and 2005. About 25% of 600 birds marked as chicks were reobserved at the natal colony. The capture and survival rates of Adélie penguins at this colony increased with the age of individuals, and five age classes were identified for both parameters. Mean adult survival was 0.85 (SE = 0.01), and no effect of sex on survival was evident. Breeding propensity, as measured by adult capture rates, was close to one, indicating a constant breeding effort through time. Temporal variations in survival were best explained by a quadratic relationship with winter sea ice extent anomalies in the Ross Sea, suggesting that for this region optimal conditions are intermediate between too much and too little winter sea ice. This is likely the result of a balance between suitable wintering habitat and food availability. Survival rates were not correlated with the Southern Oscillation Index. Low adult survival after a season characterized by severe environmental conditions at breeding but favorable conditions during winter suggested an additional mortality mediated by the reproductive effort. Adélie penguins are sensitive indicators of environmental changes in the Antarctic, and the results from this study provide insights into regional responses of this species to variability in winter sea ice habitat.