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To accurately predict species’ phenology under climate change, we need to gain a detailed mechanistic understanding of how different environmental cues interact to produce the seasonal timing response. In the winter moth (Operophtera brumata), seasonal timing of egg hatching is strongly affected by ambient temperature and has been under strong climate change-induced selection over the past 25 years. However, it is unclear whether photoperiod received at the egg stage also influences timing of egg hatching. Here, we investigated the relative contribution of photoperiod and temperature in regulating winter moth egg development using two split-brood experiments. We experimentally shifted the photoperiod eggs received by 2–4 weeks compared to the actual calendar date and measured the timing of egg hatching, both at a constant temperature and in combination with two naturally changing temperature treatments – mimicking a cold and a warm year. We found an eight-fold larger effect of temperature compared to photoperiod on egg development time. Moreover, the very small photoperiod effects we found were outweighed by both between- and within-clutch variation in egg development time. Thus, we conclude that photoperiod received at the egg stage does likely not play a substantial role in regulating the seasonal timing of egg hatching in the winter moth. These insights into the regulatory mechanism of seasonal timing could have important implications for predicting insect climate change adaptation, as we might expect different targets of selection depending on the relative contribution of different environmental cues.

The photoperiod is the main environmental cue that drives seasonal adaptive responses in reproduction, behavior, and metabolism in seasonal animals. Increasing evidence suggests that (poly)phenols contained in fruits can also modulate seasonal rhythms. (Poly)phenol-rich diets are associated with an improvement in cognitive function and neuroprotection due to their anti-inflammatory and antioxidative properties. However, it is unknown whether cherries affect neuroprotection in a photoperiod-dependent manner. To test this, F344 rats were exposed to L6 (6 h light/day), L12 (12 h light/day) and L18 (18 h light/day) photoperiods and fed a standard chow diet supplemented with either a control, lyophilized cherry 1 or cherry 2 with distinctive phenolic hallmarks. Physiological parameters (body weight, eating pattern index (EPI), testosterone, T4/T3) and hypothalamic key genes (Dio2, Dio3, Raldh1 and Ghrh) were strongly regulated by the photoperiod and/or fruit consumption. Importantly, we show for the first time that neurotrophs (Bdnf, Sod1 and Gpx1) in the hippocampus are also regulated by the photoperiod. Furthermore, the consumption of cherry 2, which was richer in total flavonols, but not cherry 1, which was richer in total anthocyanins and flavanols, enhanced neuroprotection in the hippocampus. Our results show that the seasonal consumption of cherry with a specific phenolic composition plays an important role in the hippocampal activation of neuroprotection in a photoperiod-dependent manner.

Some designs for bioregenerative life support systems to enable human space missions incorporate cyanobacteria for removal of carbon dioxide, generation of oxygen, and treatment of wastewater, as well as providing a source of nutrition. In this study, we examined the effects of the short light-dark (LD) cycle of low-Earth orbit on algal and cyanobacterial growth, approximating conditions on the International Space Station, which orbits Earth roughly every 90 min. We found that growth of green algae was similar in both normal 12 h light:12 h dark (12 h:12 h LD) and 45':45' LD cycles. Three diverse strains of cyanobacteria were not only capable of growth in short 45':45' LD cycles, but actually grew better than in 12 h:12 h LD cycles. We showed that 45':45' LD cycles do not affect the endogenous 24 h circadian rhythms of Synechococcus elongatus. Using a dense library of randomly barcoded transposon mutants, we identified genes whose loss is detrimental for the growth of S. elongatus under 45':45' LD cycles. These include several genes involved in glycogen metabolism and the oxidative pentose phosphate pathway. Notably, 45':45' LD cycles did not affect the fitness of strains that carry mutations in the biological circadian oscillator or the clock input and output regulatory pathways. Overall, this study shows that cultures of cyanobacteria could be grown under natural sunlight of low-Earth orbit and highlights the utility of a functional genomic study in a model organism to better understand key biological processes in conditions that are relevant to space travel.

The relationship between genetic differentiation and phenotypic plasticity can provide information on whether plasticity generally facilitates or hinders adaptation to environmental change. Here, we studied wing shape variation in a damselfly (Lestes sponsa) across a latitudinal gradient in Europe that differed in time constraints mediated by photoperiod and temperature. We reared damselflies from northern and southern populations in the laboratory using a reciprocal transplant experiment that simulated time-constrained (i.e. northern) and unconstrained (southern) photoperiods and temperatures. After emergence, adult wing shape was analysed using geometric morphometrics. Wings from individuals in the northern and southern populations differed significantly in shape when animals were reared in their respective native environment. Comparing wing shape across environments, we found evidence for phenotypic plasticity in wing shape, and this response differed across populations (i.e. G x E interactions). This interaction was driven by a stronger plastic response by individuals from the northern population and differences in the direction of plastic wing shape changes among populations. The alignment between genetic and plastic responses depended on the specific combination of population and rearing environment. For example, there was an alignment between plasticity and genetic differentiation under time-constrained, but not under non-time-constrained conditions for forewings. We thus find mixed support for the hypothesis that environmental plasticity and genetic population differentiation are aligned. Furthermore, although our laboratory treatments mimicked the natural climatic conditions at northern and southern latitudes, the effects of population differences on wing shape were two to four times stronger than plastic effects. We discuss our results in terms of time constraints and the possibility that natural and sexual selection is acting differently on fore- and hind

The relationship between genetic differentiation and phenotypic plasticity can provide information on whether plasticity generally facilitates or hinders adaptation to environmental change. Here, we studied wing shape variation in a damselfly (Lestes sponsa) across a latitudinal gradient in Europe that differed in time constraints mediated by photoperiod and temperature. We reared damselflies from northern and southern populations in the laboratory using a reciprocal transplant experiment that simulated time-constrained (i.e. northern) and unconstrained (southern) photoperiods and temperatures. After emergence, adult wing shape was analysed using geometric morphometrics. Wings from individuals in the northern and southern populations differed significantly in shape when animals were reared in their respective native environment. Comparing wing shape across environments, we found evidence for phenotypic plasticity in wing shape, and this response differed across populations (i.e. G x E interactions). This interaction was driven by a stronger plastic response by individuals from the northern population and differences in the direction of plastic wing shape changes among populations. The alignment between genetic and plastic responses depended on the specific combination of population and rearing environment. For example, there was an alignment between plasticity and genetic differentiation under time-constrained, but not under non-time-constrained conditions for forewings. We thus find mixed support for the hypothesis that environmental plasticity and genetic population differentiation are aligned. Furthermore, although our laboratory treatments mimicked the natural climatic conditions at northern and southern latitudes, the effects of population differences on wing shape were two to four times stronger than plastic effects. We discuss our results in terms of time constraints and the possibility that natural and sexual selection is acting differently on fore- and hind

The relationship between genetic differentiation and phenotypic plasticity can provide information on whether plasticity generally facilitates or hinders adaptation to environmental change. Here, we studied wing shape variation in a damselfly (Lestes sponsa) across a latitudinal gradient in Europe that differed in time constraints mediated by photoperiod and temperature. We reared damselflies from northern and southern populations in the laboratory using a reciprocal transplant experiment that simulated time-constrained (i.e. northern) and unconstrained (southern) photoperiods and temperatures. After emergence, adult wing shape was analysed using geometric morphometrics. Wings from individuals in the northern and southern populations differed significantly in shape when animals were reared in their respective native environment. Comparing wing shape across environments, we found evidence for phenotypic plasticity in wing shape, and this response differed across populations (i.e. G x E interactions). This interaction was driven by a stronger plastic response by individuals from the northern population and differences in the direction of plastic wing shape changes among populations. The alignment between genetic and plastic responses depended on the specific combination of population and rearing environment. For example, there was an alignment between plasticity and genetic differentiation under time-constrained, but not under non-time-constrained conditions for forewings. We thus find mixed support for the hypothesis that environmental plasticity and genetic population differentiation are aligned. Furthermore, although our laboratory treatments mimicked the natural climatic conditions at northern and southern latitudes, the effects of population differences on wing shape were two to four times stronger than plastic effects. We discuss our results in terms of time constraints and the possibility that natural and sexual selection is acting differently on fore- and hind

The relationship between genetic differentiation and phenotypic plasticity can provide information on whether plasticity generally facilitates or hinders adaptation to environmental change. Here, we studied wing shape variation in a damselfly (Lestes sponsa) across a latitudinal gradient in Europe that differed in time constraints mediated by photoperiod and temperature. We reared damselflies from northern and southern populations in the laboratory using a reciprocal transplant experiment that simulated time-constrained (i.e. northern) and unconstrained (southern) photoperiods and temperatures. After emergence, adult wing shape was analysed using geometric morphometrics. Wings from individuals in the northern and southern populations differed significantly in shape when animals were reared in their respective native environment. Comparing wing shape across environments, we found evidence for phenotypic plasticity in wing shape, and this response differed across populations (i.e. G x E interactions). This interaction was driven by a stronger plastic response by individuals from the northern population and differences in the direction of plastic wing shape changes among populations. The alignment between genetic and plastic responses depended on the specific combination of population and rearing environment. For example, there was an alignment between plasticity and genetic differentiation under time-constrained, but not under non-time-constrained conditions for forewings. We thus find mixed support for the hypothesis that environmental plasticity and genetic population differentiation are aligned. Furthermore, although our laboratory treatments mimicked the natural climatic conditions at northern and southern latitudes, the effects of population differences on wing shape were two to four times stronger than plastic effects. We discuss our results in terms of time constraints and the possibility that natural and sexual selection is acting differently on fore- and hind

Photoperiod is a common cue for seasonal plasticity and phenology, but climate change can create cue-environment mismatches for organisms that rely on it. Evolution could potentially correct these mismatches, but phenology often depends on multiple plastic decisions made during different life stages and seasons that may evolve separately. For example, Pararge aegeria (Speckled wood butterfly) has photoperiod-cued seasonal life history plasticity in two different life stages: larval development time and pupal diapause. We tested for climate change-associated evolution of this plasticity by replicating common garden experiments conducted on two Swedish populations 30 years ago. We found evidence for evolutionary change in the contemporary larval reaction norm-although these changes differed between populations-but no evidence for evolution of the pupal reaction norm. This variation in evolution across life stages demonstrates the need to consider how climate change affects the whole life cycle to understand its impacts on phenology.

A new field of research in reproductive biology was heralded by the discovery of melatonin in 1958. The concentration of melatonin follows light-dark cycles with significantly higher concentrations during darkness. The authors present the importance of the melatonin protein hormone by focusing on the reproductive processes in domestic sheep. In their literature review, they report that sheep melatonin levels show daily and seasonal rhythms. In sheep as a seasonal breeder and short-day animal species, seasonal increases in melatonin production stimulate sexual activity. The authors describe innovative possibilities for regulating melatonin levels in sheep production. The use of exogenous melatonin brings forward the expression of the sexual cycle. It increases the fertility rate, the number of lambs born, and the chances of survival of twin lambs. Melatonin is a neuroprotection compound against cerebral hypoxia and the development of inflammatory processes in the growing foetus and the newborn lamb.

The photoperiodic response is critical for plants to adjust their reproductive phase to the most favorable season. Wheat heads earlier under long days (LD) than under short days (SD) and this difference is mainly regulated by the PHOTOPERIOD1 (PPD1) gene. Tetraploid wheat plants carrying the Ppd-A1a allele with a large deletion in the promoter head earlier under SD than plants carrying the wildtype Ppd-A1b allele with an intact promoter. Phytochromes PHYB and PHYC are necessary for the light activation of PPD1, and mutations in either of these genes result in the downregulation of PPD1 and very late heading time. We show here that both effects are reverted when the phyB mutant is combined with loss-of-function mutations in EARLY FLOWERING 3 (ELF3), a component of the Evening Complex (EC) in the circadian clock. We also show that the wheat ELF3 protein interacts with PHYB and PHYC, is rapidly modified by light, and binds to the PPD1 promoter in planta (likely as part of the EC). Deletion of the ELF3 binding region in the Ppd-A1a promoter results in PPD1 upregulation at dawn, similar to PPD1 alleles with intact promoters in the elf3 mutant background. The upregulation of PPD1 is correlated with the upregulation of the florigen gene FLOWERING LOCUS T1 (FT1) and early heading time. Loss-of-function mutations in PPD1 result in the downregulation of FT1 and delayed heading, even when combined with the elf3 mutation. Taken together, these results indicate that ELF3 operates downstream of PHYB as a direct transcriptional repressor of PPD1, and that this repression is relaxed both by light and by the deletion of the ELF3 binding region in the Ppd-A1a promoter. In summary, the regulation of the light mediated activation of PPD1 by ELF3 is critical for the photoperiodic regulation of wheat heading time.

Daylength sensing in many plants is critical for coordinating the timing of flowering with the appropriate season. Temperate climate-adapted grasses such as Brachypodium distachyon flower during the spring when days are becoming longer. The photoreceptor PHYTOCHROME C is essential for long-day (LD) flowering in B. distachyon. PHYC is required for the LD activation of a suite of genes in the photoperiod pathway including PHOTOPERIOD1 (PPD1) that, in turn, result in the activation of FLOWERING LOCUS T (FT1)/FLORIGEN, which causes flowering. Thus, B. distachyon phyC mutants are extremely delayed in flowering. Here we show that PHYC-mediated activation of PPD1 occurs via EARLY FLOWERING 3 (ELF3), a component of the evening complex in the circadian clock. The extreme delay of flowering of the phyC mutant disappears when combined with an elf3 loss-of-function mutation. Moreover, the dampened PPD1 expression in phyC mutant plants is elevated in phyC/elf3 mutant plants consistent with the rapid flowering of the double mutant. We show that loss of PPD1 function also results in reduced FT1 expression and extremely delayed flowering consistent with results from wheat and barley. Additionally, elf3 mutant plants have elevated expression levels of PPD1, and we show that overexpression of ELF3 results in delayed flowering associated with a reduction of PPD1 and FT1 expression, indicating that ELF3 represses PPD1 transcription consistent with previous studies showing that ELF3 binds to the PPD1 promoter. Indeed, PPD1 is the main target of ELF3-mediated flowering as elf3/ppd1 double mutant plants are delayed flowering. Our results indicate that ELF3 operates downstream from PHYC and acts as a repressor of PPD1 in the photoperiod flowering pathway of B. distachyon.

Colostrum quality is critical to calf health as colostrum provides immunoglobulins (Ig) that are critical for a calf's immune system. Despite close management of factors known to affect colostrum production, 23% of dairy cows are still producing inadequate volume or quality of colostrum, which causes calf death and poor performance. Therefore, the objectives of this dissertation are to investigate factors that affect colostrum production and methods to improve colostrum yield and quality. Based on previous literature showing that photoperiod impacts milk yield post-calving in dry cows and that light intensity and temperature-humidity index (THI) impact colostral Ig content, I hypothesized that photoperiod and THI during the dry period impact colostrum yield and quantity in Holstein and Jersey cows. The first study evaluated the isolated effect of photoperiod on colostrum production. Dry cows were housed in a temperature-controlled barn and exposed to either short-day photoperiod (SDPP) of 8 h of light per day or long-day photoperiod (LDPP) of 16 h of light per day for the entire dry period until calving. Altered photoperiod had no effect on colostrum yield, Ig content or other components of colostrum. However, Jersey cows had a higher Brix score, fat, protein, IgA and IgM. After calving, milk production was not affected by photoperiod treatment, likely due to cows being exposed to an irregular lighting scheme. The second study evaluated the combined effects of photoperiod and THI during the dry period on colostrum production and broke cows into a bottom (1), middle (2) and top (3) third based on their photoperiod exposure. Holstein cows produced more colostrum than Jersey cows in each photoperiod category. For both breeds, photoperiod category 1 cows produced less colostrum than cows in photoperiod category 2 and 3. Brix score did not differ by breed but differed by farm and photoperiod category with farm 1, photoperiod category 3 cows having increased Brix score co

A new field of research in reproductive biology was heralded by the discovery of melatonin in 1958. The concentration of melatonin follows light-dark cycles with significantly higher concentrations during darkness. The authors present the importance of the melatonin protein hormone by focusing on the reproductive processes in domestic sheep. In their literature review, they report that sheep melatonin levels show daily and seasonal rhythms. In sheep as a seasonal breeder and short-day animal species, seasonal increases in melatonin production stimulate sexual activity. The authors describe innovative possibilities for regulating melatonin levels in sheep production. The use of exogenous melatonin brings forward the expression of the sexual cycle. It increases the fertility rate, the number of lambs born, and the chances of survival of twin lambs. Melatonin is a neuroprotection compound against cerebral hypoxia and the development of inflammatory processes in the growing foetus and the newborn lamb.

Many internal (inherent) and environmental (imposed) factors control seed dormancy and germination that we divide into three basic dormancy-release pathways: Maternal structures and embryo physiology control inherent dormancy that is broken by various types of scarification and physiological changes, followed by imposed-dormancy release when the prevailing environment is replaced by certain ‘standard’ conditions that stimulate germination (Pathway 1); imposed dormancy prevails even if inherent dormancy is broken or not applicable that is released when replaced by certain ‘standard’ environmental conditions which stimulate germination (Pathway 2); and release from inherent dormancy by light/dark or cold stratification is contingent on the pre-existence of certain environmental conditions that stimulate germination (Pathway 3). On-plant seed storage (serotiny) and frugivorous seeds are recognized here as representing special types of physical dormancy, as their properties are consistent with those of hard diaspores. Warm stratification does not require seeds to be moist as it is just a physical response. Heat may promote germination of non-hard, as well as hard, seeds as it may increase their permeability further. Levels of germination gauge the net effect of inherent- and imposed-dormancy release so that it is only possible to identify the extent of inherent-dormancy release when conditions for germination are optimal (imposed dormancy has been annulled). While imposed dormancy may be protracted after inherent dormancy is broken by heat or chilling during the dry or cold seasons, release from both states may effectively coincide if smoke chemicals or light are received during the (wet) growing season. We suggest reserving the term secondary dormancy for seeds that return to (inherent or imposed) dormancy due to changed environmental conditions. Under seasonal climates, fluctuations in environmental conditions can lead to secondary dormancy and even dormancy cycling.

Legumes have an important role in European agriculture. They assimilate N2 to sustainably support maximum crop growth, in turn providing high-protein food for human consumption and livestock feed. However, the extent of the area for legume cultivation in Europe has declined due to the lower economic competitiveness of legumes in relation to other crops, particularly of cereals and oilseed. To increase yields, there is a need to increase the genetic diversity of legumes in terms of adaptation to environmental stresses. We attempted to address this by conducting field and controlled experiments under drought vs. nondrought and different photoperiod conditions. The current study identified the physiological and agronomic traits correlated with productivity and quality performance in five economically important grain legume species (Pisum sativum, Phaseolus vulgaris, Cicer arietinum, Lupinus spp., and Vicia faba). In all species, the days to flowering and seed yield were affected by temperature and photoperiod. For cool-season legume species, long-day photoperiods were favorable and days to flowering was negatively correlated with the average air temperature. For the warm-season legumes, short-day photoperiods and warm temperatures were favorable. Under drought stress, the C/N balance, leaf nutrient (Ca, Fe, and K) concentrations, and yield were significantly reduced, contrary to Zn accumulation, and this information may contribute to improving our understanding and ability to develop sustainable growth. Based on our results, we conclude that the drought-tolerant and photoperiod-insensitive legume genotypes identified in this study constitute valuable starting materials for future programs aimed at improvement of legume productivity at a global/regional scale, which helps to strengthen the competitiveness and economic growth of legumes for European farmers.

1. Many internal (inherent) and environmental (imposed) factors control seed dormancy and germina-tion from which we can derive three basic dormancy-release pathways: Maternal structures and embryo physiology control inherent dormancy that is broken by various types of scarification and physiological changes, followed by imposed-dormancy release when replaced by certain ‘standard’ environmental conditions that stimulate germination (pathway 1); imposed dormancy prevails even if inherent dorman-cy is broken or not applicable that is released when replaced by certain ‘standard’ environmental condi-tions which stimulate germination (pathway 2); release from inherent dormancy by light/dark or cold stratification is contingent on existing presence of certain ‘standard’ environmental conditions that stim-ulate germination (pathway 3). 2. On-plant seed storage (serotiny) and frugivorous seeds are recognized here as representing special types of physical dormancy, as their properties are consistent with those of hard diaspores. Warm stratification does not require seeds to be moist as it is just a physical response. Heat may promote germination of non-hard, as well as hard, seeds as it may also increase their permeability. 3. Levels of germination gauge the net effect of inherent- and imposed-dormancy release so that it only possible to identify the extent of inherent-dormancy release when conditions for germination are optimal (imposed dormancy has been annulled). While imposed dormancy may be protracted after inherent dormancy is broken by heat or chilling during the dry or cold seasons, release from both states may effectively coincide if smoke chemicals or light are received during the (wet) growing sea-son. 4. We suggest reserving the term secondary dormancy for seeds that return to (inherent or imposed) dormancy due to changed environmental conditions. Under seasonal climates, fluctuations in envi-ronmental conditions can lead to secondary dormancy and even dormancy c

The relationship between genetic differentiation and phenotypic plasticity can provide information on whether plasticity generally facilitates or hinders adaptation to environmental change. Here, we studied wing shape variation in a damselfly (Lestes sponsa) across a latitudinal gradient in Europe that differed in time constraints mediated by photoperiod and temperature. We reared damselflies from northern and southern populations in the laboratory using a reciprocal transplant experiment that simulated time-constrained (i.e. northern) and unconstrained (southern) photoperiods and temperatures. After emergence, adult wing shape was analysed using geometric morphometrics. Wings from individuals in the northern and southern populations differed significantly in shape when animals were reared in their respective native environment. Comparing wing shape across environments, we found evidence for phenotypic plasticity in wing shape, and this response differed across populations (i.e. G x E interactions). This interaction was driven by a stronger plastic response by individuals from the northern population and differences in the direction of plastic wing shape changes among populations. The alignment between genetic and plastic responses depended on the specific combination of population and rearing environment. For example, there was an alignment between plasticity and genetic differentiation under time-constrained, but not under non-time-constrained conditions for forewings. We thus find mixed support for the hypothesis that environmental plasticity and genetic population differentiation are aligned. Furthermore, although our laboratory treatments mimicked the natural climatic conditions at northern and southern latitudes, the effects of population differences on wing shape were two to four times stronger than plastic effects. We discuss our results in terms of time constraints and the possibility that natural and sexual selection is acting differently on fore- and hind

[Aims] Shifts in xylem phenology directly determine the forest capacity for carbon sequestration. However, a systematic understanding of the spatial patterns and the underpinning drivers in determining the cessation of wood formation (Ccw) is lacking at a pan-continental scale. Here, we addressed this knowledge gap by compiling a new dataset of multiple xylem phenology timings for northern conifers., [Locations] Sixty-two study sites, Northern Hemisphere (25–55° N)., [Time period] 2003–2018 (16 years)., [Taxa] Thirty-three conifer species., [Methods] A generalized additive model was fitted to characterize the latitudinal pattern in Ccw. Structural equation modelling and a linear mixed-effects model were applied to determine the main drivers underlying the latitudinal pattern in Ccw., [Results] The Ccw followed a flat S-shaped pattern with increasing latitude. Photoperiod was the dominant determinant of the latitudinal pattern of Ccw, and a longer photoperiod was associated with an earlier Ccw. Both mean growing-season temperature and total growing-season precipitation exhibited significantly positive relationships to the cessation of cell elongation and thus the Ccw across all study sites. In arid regions, the pre-growing-season temperature had a significantly negative effect on Ccw. In humid regions, Ccw was positively affected by the mean growing-season temperature. The onset of wood formation showed significantly positive coupling with Ccw at arid sites but not at humid sites. Early successional species were sensitive to hydrothermal variations during the pre-growing season., [Main conclusions] We reveal the dominant role of photoperiod in determining the cessation of wood formation for northern conifers and highlight differentiated interactive effects between photoperiod and seasonal climatic factors and the preceding xylem phenophases in determining Ccw among ecoregions and tree species. These insights provide evidence to reduce uncertainty in prediction of the forest carbon uptake potential and the consequent biophysical feedbacks of northern forests.

Despite growing interest in predicting plant phenological shifts, advanced spring phenology by global climate change remains debated. Evidence documenting either small or large advancement of spring phenology to rising temperature over the spatio-temporal scales implies a potential existence of a thermal threshold in the responses of forests to global warming. We collected a unique data set of xylem cell-wall-thickening onset dates in 20 coniferous species covering a broad mean annual temperature (MAT) gradient (−3.05 to 22.9°C) across the Northern Hemisphere (latitudes 23°–66° N). Along the MAT gradient, we identified a threshold temperature (using segmented regression) of 4.9 ± 1.1°C, above which the response of xylem phenology to rising temperatures significantly decline. This threshold separates the Northern Hemisphere conifers into cold and warm thermal niches, with MAT and spring forcing being the primary drivers for the onset dates (estimated by linear and Bayesian mixed-effect models), respectively. The identified thermal threshold should be integrated into the Earth-System-Models for a better understanding of spring phenology in response to global warming and an improved prediction of global climate-carbon feedbacks.

The beneficial health effects of (poly)phenol-rich foods such as red grapes mainly depend on both the type and concentration of (poly)phenols. Since fruit (poly)phenol content is influenced by growing conditions, the study examines the seasonal effects of red grapes (Vitis vinifera L.), grown under various cultivation conditions, on metabolic markers of adipose tissue in healthy rats.For this purpose, Fischer 344 rats are exposed into three different light-dark cycles and daily supplemented with 100 mg kg-1 of either conventionally or organically grown red grapes for 10 weeks (n = 6). Seasonal consumption of organic grapes (OGs), which are richer in anthocyanins, increases energy expenditure (EE) of animals exposed to long photoperiod and enhances uncoupling protein 1 (UCP1) protein expression in brown adipose tissue of animals under standard photoperiod. Additionally, red grape consumption affects the gene expression profile of white adipose tissue (WAT), upregulating browning markers of subcutaneous WAT in 12 h light (L12) and 18 h light (L18) photoperiods, and downregulating adipogenic and lipolytic markers of visceral WAT in 6 h light (L6) and L12 photoperiods.These results clearly show that bioactive compounds of grapes can modulate the metabolic markers of white and brown adipose tissues in a photoperiod and depot-dependent manner, partly affecting EE when consumed out of season.© 2023 The Authors. Molecular Nutrition & Food Research published by Wiley-VCH GmbH.

Energy homeostasis and metabolism in mammals are strongly influenced by seasonal changes. Variations in photoperiod patterns drive adaptations in body weight and adiposity, reflecting changes in the regulation of food intake and energy expenditure. Humans also show distinct patterns of energy balance depending on the season, being more susceptible to gaining weight during a specific time of the year. Changes in body weight are mainly reflected by the adipose tissue, which is a key metabolic tissue and is highly affected by circannual rhythms. Mostly, in summer-like (long-active) photoperiod, adipocytes adopt a rather anabolic profile, more predisposed to store energy, while food intake increases and energy expenditure is reduced. These metabolic adaptations involve molecular modifications, some of which have been studied during the last years and are summarized in this review. In addition, there is a bidirectional relation between obesity and the seasonal responses, with obesity disrupting some of the seasonal responses observed in healthy mammals, and altered seasonality being highly associated with increased risk of developing obesity. This suggests that changes in photoperiod produce important metabolic alterations in healthy organisms. Biological rhythms impact the regulation of metabolism to different extents, some of which are already known, but further research is needed to fully understand the relationship between energy balance and seasonality.

Plants possess regulatory mechanisms that allow them to flower under conditions that maximize reproductive success. Selection of natural variants affecting those mechanisms has been critical in agriculture to modulate the flowering response of crops to specific environments and to increase yield. In the temperate cereals, wheat and barley, the photoperiod and vernalization pathways explain most of the natural variation in flowering time. However, other pathways also participate in fine-tuning the flowering response. In this work, we integrate the conserved microRNA miR172 and its targets APETALA2-like (AP2L) genes into the temperate grass flowering network involving VERNALIZATION 1 (VRN1), VRN2 and FLOWERING LOCUS T 1 (FT1 = VRN3) genes. Using mutants, transgenics and different growing conditions, we show that miR172 promotes flowering in wheat, while its target genes AP2L1 (TaTOE1) and AP2L5 (Q) act as flowering repressors. Moreover, we reveal that the miR172-AP2L pathway regulates FT1 expression in the leaves, and that this regulation is independent of VRN2 and VRN1. In addition, we show that the miR172-AP2L module and flowering are both controlled by plant age through miR156 in spring cultivars. However, in winter cultivars, flowering and the regulation of AP2L1 expression are decoupled from miR156 downregulation with age, and induction of VRN1 by vernalization is required to repress AP2L1 in the leaves and promote flowering. Interestingly, the levels of miR172 and both AP2L genes modulate the flowering response to different vernalization treatments in winter cultivars. In summary, our results show that conserved and grass specific gene networks interact to modulate the flowering response, and that natural or induced mutations in AP2L genes are useful tools for fine-tuning wheat flowering time in a changing environment.

Unidad de excelencia María de Maeztu CEX2019-000940-M, Fluctuations in environmental conditions greatly influence life on earth. Plants, as sessile organisms, have developed molecular mechanisms to adapt their development to changes in daylength, or photoperiod. One of the first plant features that comes to mind as affected by the duration of the day is flowering time; we all bring up a clear image of spring blossom. However, for many plants flowering happens at other times of the year, and many other developmental aspects are also affected by changes in daylength, which range from hypocotyl elongation in Arabidopsis thaliana to tuberization in potato or autumn growth cessation in trees. Strikingly, many of the processes affected by photoperiod employ similar gene networks to respond to changes in the length of light/dark cycles. In this review, we have focused on developmental processes affected by photoperiod that share similar genes and gene regulatory networks.

In perennial fruit and berry crops of the Rosaceae family, flower initiation occurs in late summer or autumn after downregulation of a strong repressor TERMINAL FLOWER1 (TFL1), and flowering and fruiting takes place the following growing season. Rosaceous fruit trees typically form two types of axillary shoots, short flower-bearing shoots called spurs and long shoots that are, respectively, analogous to branch crowns and stolons in strawberry. However, regulation of flowering and shoot architecture differs between species, and environmental and endogenous controlling mechanisms have just started to emerge. In woodland strawberry (Fragaria vesca L.), long days maintain vegetative meristems and promote stolon formation by activating TFL1 and GIBBERELLIN 20-OXIDASE4 (GA20ox4), respectively, while silencing of these factors by short days and cool temperatures induces flowering and branch crown formation. We characterized flowering responses of 14 accessions of seven diploid Fragaria species native to diverse habitats in the northern hemisphere and selected two species with contrasting environmental responses, Fragaria bucharica Losinsk. and Fragaria nilgerrensis Schlecht. ex J. Gay for detailed studies together with Fragaria vesca. Similar to F. vesca, short days at 18°C promoted flowering in F. bucharica, and the species was induced to flower regardless of photoperiod at 11°C after silencing of TFL1. F. nilgerrensis maintained higher TFL1 expression level and likely required cooler temperatures or longer exposure to inductive treatments to flower. We also found that high expression of GA20ox4 was associated with stolon formation in all three species, and its downregulation by short days and cool temperature coincided with branch crown formation in F. vesca and F. nilgerrensis, although the latter did not flower. F. bucharica, in contrast, rarely formed branch crowns, regardless of flowering or GA20ox4 expression level. Our findings highlighted diploid Fragaria species, Peer Reviewed

The hoverfly Sphaerophoria rueppellii is currently one of the most effective predators commercially available for aphid pest control. However, knowledge of the reproductive system of males and females of this syrphid is limited. The present article aims to report how changes in the temperature and photoperiod may affect development of the gonads (ovaries and testes), oviposition, and fecundity during the lifespan of S. rueppellii. Four environmental conditions (14L:10D, T: 20 ± 1 °C; 12L:12D, T: 20 ± 1 °C; 14L:10D, T: 25 ± 1 °C; and 12L:12D, T: 25 ± 1 °C) were used to determine oviposition, hatching percentage, and lifespan during a period of 30 days after the adult emergence. The maturation of the ovaries was done under three treatments (barley leaves with aphids always available; barley leaves two days per week with aphids available; no barley leaves available), and in the same environmental conditions noted above. Males at 14L:10D, 20 ± 1 °C; and 14L:10D, 25 ± 1 °C; were used to analyze and study the maturation of the testes. Females at 14L:10D; T: 25 ± 1 °C showed a significant difference in oviposition, percentage of hatching, and rate of eggs. A detailed description of the male and female gonads was undertaken, and it was determined that the conditions in which males sexually mature early are at 14L:10D, 25 ± 1 °C. These results will improve the application of S. rueppellii in crops, for the control of aphid pests.

This study examines whether the photostimulation of sexual activity in young bucks improves the reproductive performance of the "male effect" in comparison to adult males. The experimental design was a 2 × 2 with to variables: age of bucks and photoperiodic treatment of bucks. Ninety-three anoestrous does were distributed into four groups depending on the kind of male used: young bucks (1.26 years old, n = 6) or old bucks (5.15 years old, n = 6). Half of each group of males were subjected to a photoperiodic treatment or a natural photoperiod. After the males were introduced, the sexual behaviour of the bucks was assessed for 10 days, and doe oestrous behaviour was recorded. Ovulation was confirmed from plasma progesterone concentration, and ovulation rate was assessed by transrectal ultrasonography. Fecundity, fertility, prolificacy and productivity were also determined. The females in contact with young bucks showed a higher percentage of ovulation (100% vs 81%, P < 0.01) and oestrous (82% vs 64%, P < 0.05) than females in contact with old bucks. The females in contact with photostimulated bucks showed higher percentages of oestrous (88% vs 60%, P < 0.01), fertility (78% vs 44%, P < 0.01) and productivity (1.08 ± 0.10 vs 0.60 ± 0.12 P < 0.01) than females in contact with control bucks. No interaction between both factors (age and photoperiod treatment) on any studied variable was observed. In conclusion, the response to the "male effect" was higher when using young bucks or photostimulated bucks. These photostimulated bucks produced 48 additional kids for every 100 females in the mating group compared to does exposed to untreated bucks.

Two experiments were carried out. Firstly, 54 anestrous females were placed in contact with photostimulated males (Photo; n = 27) or with no photostimulated males (Natural; n = 27). Moreover, a group of bucks treated with artificial photoperiod and a group of bucks subjected to natural photoperiod without contact with females was used (Photo Isolated and Natural Isolated, respectively). In the Natural groups, the testosterone concentrations were similar except for three days after the introduction of the bucks to the does (19.72 ± 4.11 vs. 2.05 ± 0.25 ng/mL for Natural and Natural isolated bucks, respectively, p < 0.05). However, no differences were observed in the Photo groups during the entire experiment. The percentage of females showing estrous was higher in the group of females in contact with photostimulated bucks (96 vs. 74%, respectively, p < 0.05). In the second experiment, a GnRH agonist, deslorelin, was used to regulate the testosterone concentrations of the bucks. Seventy anestrous females were divided into five groups depending on the treatment received by the bucks to which they were exposed: photostimulated bucks (Photo group, n = 14); photostimulated bucks but treated with the agonist at the onset of the photoperiod treatment (Photo-Ago Long group, n = 13); photostimulated bucks but treated with the agonist at the end of the photoperiod treatment (Photo-Ago Short group, n = 15); bucks receiving no photostimulation but treated with the agonist at the end of the photoperiod treatment period (Natural-Ago Short group, n = 13) and bucks receiving no photostimulation nor agonist (Natural group, n = 15). The agonist treatment increased testosterone concentrations after the injection, which remained high for the entire experiment (p < 0.05). Six days after the introduction of the bucks to the does, the testosterone concentrations increased only in the Natural group reaching similar concentrations to the other groups (12.17 ± 6.55, 16.69 ± 4.53, 8.70 ± 0.61

Using a perennial model plant allows the study of reoccurring seasonal events in a way that is not possible using a fast-growing annual such as A. thaliana (Arabidopsis). In this study, we present a hybrid aspen (Populus tremula × P. tremuloides) as our perennial model plant. These plants can be grown in growth chambers to shorten growth periods and manipulate day length and temperature in ways that would be impossible under natural conditions. In addition, the use of growth chambers allows easy monitoring of height and diameter expansion, accelerating the collection of data from new strategies that allow evaluation of promoters or inhibitors of growth. Here, we describe how to study and quantify responses to seasonal changes (mainly using P. tremula × P. tremuloides) by measuring growth rate and key events under different photoperiodic cycles.

The vagus nerve is considered to play a key role in the circadian rhythm. Chronic continuous analysis of the vagus nerve activity could contribute to a better understanding of the role of the vagus nerve in light-dark modulations. This paper presents a continuous analysis of spontaneous vagus nerve activity performed in four rats.We analyzed the vagus electroneurogram (VENG) and electroencephalogram (EEG) over a recording period of 28 d. Spike activity and heart rate estimation were derived from the VENG, and slow-wave activity was derived from the EEG. The presence of repetitive patterns was investigated with periodograms, cosinor fitting, autocorrelation, and statistical tests. The light-dark variations derived from the VENG spikes were compared with EEG slow waves, an established metric in circadian studies.Our results demonstrate that light-dark variations can be detected in long-term vagus nerve activity monitoring. A recording period of about 7 d is required to characterize accurately the VENG light-dark variations.As a major outcome of this study, vagus nerve recordings hold the promise to help understand circadian regulation.

Animals adapt their seasonal physiology by measuring photoperiodic changes over the calendar year. A new study in PLOS Biology uncovers changes in glutamate dynamics in the bean bug that are dependent on photoperiod and a clock gene.

Circadian alignment of rest-activity rhythms is an essential biological process that may be vulnerable to misalignment in critically ill patients. We evaluated circadian rest-activity rhythms in critically ill patients and their association with baseline (e.g. age) and clinical (e.g. mechanical ventilation status) variables, along with intensive care unit light-dark cycles. Using wrist actigraphy, we collected 48-hr activity and light exposure data from critically ill patients in a tertiary care medical intensive care unit. We evaluated circadian rest-activity rhythms using COSINOR and non-parametric circadian rhythm analysis models, and stratified these data across baseline and clinical variables. We used linear regression to evaluate the association of circadian rest-activity and light-dark exposure rhythms. In COSINOR and non-parametric circadian rhythm analysis analyses, the 34 medical intensive care unit patients completing 48-hr actigraphy recordings exhibited mean MESOR (mean activity levels of a fitted curve) and amplitudes of 0.50 ± 0.32 and 0.20 ± 0.19 movements per 30-s epoch, with high interdaily variability. Patients who were older, mechanically ventilated, sedated, restrained and with higher organ failure scores tended to exhibit greater circadian rest-activity misalignment, with three of 34 (9%) patients exhibiting no circadian rhythmicity. Circadian light-dark exposure misalignment was observed as well and was associated with rest-activity misalignment (p = 0.03). Critically ill patients in our MICU experienced profound circadian rest-activity misalignment, with mostly weak or absent rhythms, along with circadian light-dark exposure misalignment. Potentially modifiable factors contributing to rest-activity misalignment (i.e. mechanical ventilation, restraints, low daytime light levels) highlight possible targets for future improvement efforts.

Plants possess regulatory mechanisms that allow them to flower under conditions that maximize reproductive success. Selection of natural variants affecting those mechanisms has been critical in agriculture to modulate the flowering response of crops to specific environments and to increase yield. In the temperate cereals, wheat and barley, the photoperiod and vernalization pathways explain most of the natural variation in flowering time. However, other pathways also participate in fine-tuning the flowering response. In this work, we integrate the conserved microRNA miR172 and its targets APETALA2-like (AP2L) genes into the temperate grass flowering network involving VERNALIZATION 1 (VRN1), VRN2 and FLOWERING LOCUS T 1 (FT1 = VRN3) genes. Using mutants, transgenics and different growing conditions, we show that miR172 promotes flowering in wheat, while its target genes AP2L1 (TaTOE1) and AP2L5 (Q) act as flowering repressors. Moreover, we reveal that the miR172-AP2L pathway regulates FT1 expression in the leaves, and that this regulation is independent of VRN2 and VRN1. In addition, we show that the miR172-AP2L module and flowering are both controlled by plant age through miR156 in spring cultivars. However, in winter cultivars, flowering and the regulation of AP2L1 expression are decoupled from miR156 downregulation with age, and induction of VRN1 by vernalization is required to repress AP2L1 in the leaves and promote flowering. Interestingly, the levels of miR172 and both AP2L genes modulate the flowering response to different vernalization treatments in winter cultivars. In summary, our results show that conserved and grass specific gene networks interact to modulate the flowering response, and that natural or induced mutations in AP2L genes are useful tools for fine-tuning wheat flowering time in a changing environment.

Two experiments were carried out. Firstly, 54 anestrous females were placed in contact with photostimulated males (Photo; n = 27) or with no photostimulated males (Natural; n = 27). Moreover, a group of bucks treated with artificial photoperiod and a group of bucks subjected to natural photoperiod without contact with females was used (Photo Isolated and Natural Isolated, respectively). In the Natural groups, the testosterone concentrations were similar except for three days after the introduction of the bucks to the does (19.72 ± 4.11 vs. 2.05 ± 0.25 ng/mL for Natural and Natural isolated bucks, respectively, p < 0.05). However, no differences were observed in the Photo groups during the entire experiment. The percentage of females showing estrous was higher in the group of females in contact with photostimulated bucks (96 vs. 74%, respectively, p < 0.05). In the second experiment, a GnRH agonist, deslorelin, was used to regulate the testosterone concentrations of the bucks. Seventy anestrous females were divided into five groups depending on the treatment received by the bucks to which they were exposed: photostimulated bucks (Photo group, n = 14); photostimulated bucks but treated with the agonist at the onset of the photoperiod treatment (Photo-Ago Long group, n = 13); photostimulated bucks but treated with the agonist at the end of the photoperiod treatment (Photo-Ago Short group, n = 15); bucks receiving no photostimulation but treated with the agonist at the end of the photoperiod treatment period (Natural-Ago Short group, n = 13) and bucks receiving no photostimulation nor agonist (Natural group, n = 15). The agonist treatment increased testosterone concentrations after the injection, which remained high for the entire experiment (p < 0.05). Six days after the introduction of the bucks to the does, the testosterone concentrations increased only in the Natural group reaching similar concentrations to the other groups (12.17 ± 6.55, 16.69 ± 4.53, 8.70 ± 0.61

This study examines whether the photostimulation of sexual activity in young bucks improves the reproductive performance of the "male effect" in comparison to adult males. The experimental design was a 2 × 2 with to variables: age of bucks and photoperiodic treatment of bucks. Ninety-three anoestrous does were distributed into four groups depending on the kind of male used: young bucks (1.26 years old, n = 6) or old bucks (5.15 years old, n = 6). Half of each group of males were subjected to a photoperiodic treatment or a natural photoperiod. After the males were introduced, the sexual behaviour of the bucks was assessed for 10 days, and doe oestrous behaviour was recorded. Ovulation was confirmed from plasma progesterone concentration, and ovulation rate was assessed by transrectal ultrasonography. Fecundity, fertility, prolificacy and productivity were also determined. The females in contact with young bucks showed a higher percentage of ovulation (100% vs 81%, P < 0.01) and oestrous (82% vs 64%, P < 0.05) than females in contact with old bucks. The females in contact with photostimulated bucks showed higher percentages of oestrous (88% vs 60%, P < 0.01), fertility (78% vs 44%, P < 0.01) and productivity (1.08 ± 0.10 vs 0.60 ± 0.12 P < 0.01) than females in contact with control bucks. No interaction between both factors (age and photoperiod treatment) on any studied variable was observed. In conclusion, the response to the "male effect" was higher when using young bucks or photostimulated bucks. These photostimulated bucks produced 48 additional kids for every 100 females in the mating group compared to does exposed to untreated bucks.

Advancing spring phenology due to climate change can result in different behavioural responses in long-distance migratory birds, such advancement in their spring arrival date. However, the degree to which timing is flexible to environmental change and the underlying mechanisms require further investigation. To investigate timekeeping systems in free-living long-distance migratory birds (purple martin Progne subis) in a natural ecosystem, this thesis used the ‘wild clock’ approach, which is the combination of chronobiology and ecology. Birds may flexibly respond to advancing springs if earlier first egg dates expose hatched birds to different environmental cues, such as photoperiod, which they may use to synchronize their internal clock time (ontogenetic effect). I found that nest timing (first egg date) was an influential factor on the post-breeding movement timing (fledge date and colony departure date) in a wild population of purple martins. I used an experimental approach to further explore the phenotypic plasticity of young purple martins to photoperiod experienced in the nest. With a simulated, early photoperiod I found that exposed nestlings had a longer nesting period and later fledge and autumn departure dates than birds that experienced natural day length. I also found that an anthropogenic light at night (ALAN) treatment changed the timing of post-breeding movements, where nestlings exposed to white light had higher weight and later colony departure date than young who experienced green light and natural darkness. Lastly, I investigated the impact of aging on timing. Using data for 1-5 year old birds, I found that spring migration timing and the timing of nesting advanced as birds age, which may reflect the effects of experience or that optimal time is under different time selection pressures as birds age. Overall, this study contributes to our understanding of the synchronization of internal clock time during nestling development with one of the most impo

The pullets of Indian Rhode Island Red (RIR) breed of domestic fowl were reared under a step-down photoperiod of LD 18:6 (long photoperiod; LP) from day 1 to day 90 post-hatch, and then shifted to LD 12:12 (NLD), to assess its effect on growth kinetics of lymphoid and reproductive organs, and serum hormone profiles, the observations were made at 30,60 and 90 days and the results were compared with pullets reared under NLD alone. The weights of thyroid and ovary in LP chicks showed significant increment, whereas the weights of liver and lymphoid organs were identical to that of NLD chicks. The weights of adrenal and oviduct decreased significantly. In general, serum levels of T3, T4, corticosterone and progesterone tended to show a gradual decrement with age in NLD chicks, but the LP chicks showed a differential change marked by high T3 and T4 levels throughout and, increased corticosterone and decreased progesterone levels at 30 and 60 days. Long photoperiod seems to have an initial depressive, but later stimulatory effect on growth of thyroid, while it has an Inhibitory effect on adrenal. The histometric data of ovary suggest a stimulatory effect of light, indicated by increased number of follicles and decreased degree of follicular atresia. It is concluded from the present observations that exposure of chicks to LP has differential effects on growth kinetics and, a favourable influence on reproductive hormones suggesting inherent photosensitivity and, no setting in of photorefractoriness during this period.

Plant phenology, i. e. the timing of life cycle events, is related to individual fitness and species distributionranges. Temperature is one of the most important drivers of plant phenology together with day length.The adaptation of their phenology may be important for the success of invasive plant species. The presentstudy aims at understanding how the performance and the phenology of the invasive legume Lupinuspolyphyllus vary with latitude. We sampled data across a >2000 km latitudinal gradient from Centralto Northern Europe. We quantified variation in phenology of flowering and fruiting of L. polyphyllususing >1600 digital photos of inflorescences from 220 individual plants observed weekly at 22 sites. Theday of the year at which different phenological phases were reached, increased 1.3–1.8 days per degreelatitude, whereas the growing degree days (gdd) required for these phenological phases decreased 5–16 gddper degree latitude. However, this difference disappeared, when the day length of each day included inthe calculation of gdd was considered. The day of the year of the earliest and the latest climatic zone toreach any of the three studied phenological phases differed by 23–30 days and temperature requirementsto reach these stages differed between 62 and 236 gdd. Probably, the invasion of this species will furtherincrease in the northern part of Europe over the next decades due to climate warming. For invasive speciescontrol, our results suggest that in countries with a large latitudinal extent, the mowing date should shiftby ca. one week per 500 km at sites with similar elevations.

The pullets of Indian Rhode Island Red (RIR) breed of domestic fowl were reared under a step-down photoperiod of LD 18:6 (long photoperiod; LP) from day 1 to day 90 post-hatch, and then shifted to LD 12:12 (NLD), to assess its effect on growth kinetics of lymphoid and reproductive organs, and serum hormone profiles, the observations were made at 30,60 and 90 days and the results were compared with pullets reared under NLD alone. The weights of thyroid and ovary in LP chicks showed significant increment, whereas the weights of liver and lymphoid organs were identical to that of NLD chicks. The weights of adrenal and oviduct decreased significantly. In general, serum levels of T3, T4, corticosterone and progesterone tended to show a gradual decrement with age in NLD chicks, but the LP chicks showed a differential change marked by high T3 and T4 levels throughout and, increased corticosterone and decreased progesterone levels at 30 and 60 days. Long photoperiod seems to have an initial depressive, but later stimulatory effect on growth of thyroid, while it has an Inhibitory effect on adrenal. The histometric data of ovary suggest a stimulatory effect of light, indicated by increased number of follicles and decreased degree of follicular atresia. It is concluded from the present observations that exposure of chicks to LP has differential effects on growth kinetics and, a favourable influence on reproductive hormones suggesting inherent photosensitivity and, no setting in of photorefractoriness during this period.

Genetically encoded biological clocks are found broadly throughout life on Earth, where they generate circadian (about a day) rhythms that synchronize physiology and behavior with the daily light/dark cycle. Although the genetic networks that give rise to circadian timing are now fairly well established, our understanding of how the proteins that constitute the molecular 'cogs' of this biological clock regulate the intrinsic timing, or period, of circadian rhythms has lagged behind. New studies probing the biochemical and structural basis of clock protein function are beginning to reveal how assemblies of dedicated clock proteins form and evolve through post-translational regulation to generate circadian rhythms. This review will highlight some recent advances providing important insight into the molecular mechanisms of period control in mammalian clocks with an emphasis on structural analyses related to CK1-dependent control of PER stability.

The field of neuropsychopharmacology relies on behavioral assays to quantify behavioral processes related to mental illness and substance use disorders. Although these assays have been highly informative, sometimes laboratories have unpublished datasets from experiments that "didn't work". Often this is because expected outcomes were not observed in positive or negative control groups. While this can be due to experimenter error, an important alternative is that under-appreciated environmental factors can have a major impact on results. "Hidden variables" such as circadian cycles, husbandry, and social environments are often omitted in methods sections, even though there is a strong body of literature documenting their impact on physiological and behavioral outcomes. Applying this knowledge in a more critical manner could provide behavioral neuroscientists with tools to develop better testing methods, improve the external validity of behavioral techniques, and make better comparisons of experimental data across institutions. Here we review the potential impact of "hidden variables" that are commonly overlooked such as light-dark cycles, transport stress, cage ventilation, and social housing structure. While some of these conditions may not be under direct control of investigators, it does not diminish the potential impact of these variables on experimental results. We provide recommendations to investigators on which variables to report in publications and how to address "hidden variables" that impact their experimental results.

Plant phenology, i. e. the timing of life cycle events, is related to individual fitness and species distributionranges. Temperature is one of the most important drivers of plant phenology together with day length.The adaptation of their phenology may be important for the success of invasive plant species. The presentstudy aims at understanding how the performance and the phenology of the invasive legume Lupinuspolyphyllus vary with latitude. We sampled data across a >2000 km latitudinal gradient from Centralto Northern Europe. We quantified variation in phenology of flowering and fruiting of L. polyphyllususing >1600 digital photos of inflorescences from 220 individual plants observed weekly at 22 sites. Theday of the year at which different phenological phases were reached, increased 1.3–1.8 days per degreelatitude, whereas the growing degree days (gdd) required for these phenological phases decreased 5–16 gddper degree latitude. However, this difference disappeared, when the day length of each day included inthe calculation of gdd was considered. The day of the year of the earliest and the latest climatic zone toreach any of the three studied phenological phases differed by 23–30 days and temperature requirementsto reach these stages differed between 62 and 236 gdd. Probably, the invasion of this species will furtherincrease in the northern part of Europe over the next decades due to climate warming. For invasive speciescontrol, our results suggest that in countries with a large latitudinal extent, the mowing date should shiftby ca. one week per 500 km at sites with similar elevations.

Advancing spring phenology due to climate change can result in different behavioural responses in long-distance migratory birds, such advancement in their spring arrival date. However, the degree to which timing is flexible to environmental change and the underlying mechanisms require further investigation. To investigate timekeeping systems in free-living long-distance migratory birds (purple martin Progne subis) in a natural ecosystem, this thesis used the ‘wild clock’ approach, which is the combination of chronobiology and ecology. Birds may flexibly respond to advancing springs if earlier first egg dates expose hatched birds to different environmental cues, such as photoperiod, which they may use to synchronize their internal clock time (ontogenetic effect). I found that nest timing (first egg date) was an influential factor on the post-breeding movement timing (fledge date and colony departure date) in a wild population of purple martins. I used an experimental approach to further explore the phenotypic plasticity of young purple martins to photoperiod experienced in the nest. With a simulated, early photoperiod I found that exposed nestlings had a longer nesting period and later fledge and autumn departure dates than birds that experienced natural day length. I also found that an anthropogenic light at night (ALAN) treatment changed the timing of post-breeding movements, where nestlings exposed to white light had higher weight and later colony departure date than young who experienced green light and natural darkness. Lastly, I investigated the impact of aging on timing. Using data for 1-5 year old birds, I found that spring migration timing and the timing of nesting advanced as birds age, which may reflect the effects of experience or that optimal time is under different time selection pressures as birds age. Overall, this study contributes to our understanding of the synchronization of internal clock time during nestling development with one of the most impo

Two experiments were carried out. Firstly, 54 anestrous females were placed in contact with photostimulated males (Photo; n = 27) or with no photostimulated males (Natural; n = 27). Moreover, a group of bucks treated with artificial photoperiod and a group of bucks subjected to natural photoperiod without contact with females was used (Photo Isolated and Natural Isolated, respectively). In the Natural groups, the testosterone concentrations were similar except for three days after the introduction of the bucks to the does (19.72 ± 4.11 vs. 2.05 ± 0.25 ng/mL for Natural and Natural isolated bucks, respectively, p < 0.05). However, no differences were observed in the Photo groups during the entire experiment. The percentage of females showing estrous was higher in the group of females in contact with photostimulated bucks (96 vs. 74%, respectively, p < 0.05). In the second experiment, a GnRH agonist, deslorelin, was used to regulate the testosterone concentrations of the bucks. Seventy anestrous females were divided into five groups depending on the treatment received by the bucks to which they were exposed: photostimulated bucks (Photo group, n = 14); photostimulated bucks but treated with the agonist at the onset of the photoperiod treatment (Photo-Ago Long group, n = 13); photostimulated bucks but treated with the agonist at the end of the photoperiod treatment (Photo-Ago Short group, n = 15); bucks receiving no photostimulation but treated with the agonist at the end of the photoperiod treatment period (Natural-Ago Short group, n = 13) and bucks receiving no photostimulation nor agonist (Natural group, n = 15). The agonist treatment increased testosterone concentrations after the injection, which remained high for the entire experiment (p < 0.05). Six days after the introduction of the bucks to the does, the testosterone concentrations increased only in the Natural group reaching similar concentrations to the other groups (12.17 ± 6.55, 16.69 ± 4.53, 8.70 ± 0.61

The pullets of Indian Rhode Island Red (RIR) breed of domestic fowl were reared under a step-down photoperiod of LD 18:6 (long photoperiod; LP) from day 1 to day 90 post-hatch, and then shifted to LD 12:12 (NLD), to assess its effect on growth kinetics of lymphoid and reproductive organs, and serum hormone profiles, the observations were made at 30,60 and 90 days and the results were compared with pullets reared under NLD alone. The weights of thyroid and ovary in LP chicks showed significant increment, whereas the weights of liver and lymphoid organs were identical to that of NLD chicks. The weights of adrenal and oviduct decreased significantly. In general, serum levels of T3, T4, corticosterone and progesterone tended to show a gradual decrement with age in NLD chicks, but the LP chicks showed a differential change marked by high T3 and T4 levels throughout and, increased corticosterone and decreased progesterone levels at 30 and 60 days. Long photoperiod seems to have an initial depressive, but later stimulatory effect on growth of thyroid, while it has an Inhibitory effect on adrenal. The histometric data of ovary suggest a stimulatory effect of light, indicated by increased number of follicles and decreased degree of follicular atresia. It is concluded from the present observations that exposure of chicks to LP has differential effects on growth kinetics and, a favourable influence on reproductive hormones suggesting inherent photosensitivity and, no setting in of photorefractoriness during this period.