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To elucidate the mechanisms underlying photoperiodic responses, we investigated the genomic and metabolomic responses of two broomcorn millet (Panicum miliaceum L.) genotypes. For this purpose, light-insensitive (D32) and light-sensitive (M51) genotypes were exposed to a 16 h photoperiod (long-day (LD) conditions) and an 8 h photoperiod (short-day (SD) conditions), and various transcriptomic and metabolomic changes were investigated. A total of 1664, 2564, 13,017, and 15548 DEGs were identified in the SD-D, LD-D, LD-M, and SD-M groups, respectively. Furthermore, 112 common DEGs were identified as well. Interestingly, most DEGs in the different groups were associated with photosynthesis and phenylpropanoid and carotenoid biosynthesis. In addition, 822 metabolites were identified under different treatments. The main metabolites, including L-malic and fumaric acids, were identified in the negative mode, whereas brucine and loperamide were identified in the positive mode. KEGG analysis revealed that the metabolites in the different groups were enriched in the same metabolic pathway of the TCA cycle. Furthermore, in negative mode, the metabolites of M51 were mainly D-glucose, whereas those of D32 were mainly L-malic and fumaric acids. One photoperiod candidate gene (C2845_PM11G01290), annotated as ATP6B, significantly increased the levels of L-malic and fumaric acids. In conclusion, our study provides a theoretical basis for understanding the molecular mechanisms of photoperiodic response regulation and can be used as a reference for marker development and resource identification in Panicum miliaceum L.. [ABSTRACT FROM AUTHOR]

The identity and nature of the photoperiodic photoreceptors are now quite well known, as is the nature of the endocrine regulation of the resulting diapauses. The central problem of time measurement—how the photoperiodic clock differentiates long from short days—however, is still obscure, known only from whole-animal experiments and abstract models, although it is clearly a function of the insect circadian system. This review describes some of these experiments in terms of oscillator entrainment and two widely applicable photoperiodic clock models, external and internal coincidence, mainly using data from experiments on flesh flies (Sarcophaga spp) and the parasitic wasp, Nasonia vitripennis. [ABSTRACT FROM AUTHOR]

In 1976, Pittendrigh and Daan established a theoretical framework which has coordinated research on circadian clock entrainment and photoperiodism until today. The "wild clocks" approach, which concerns studying wild species in their natural habitats, has served to test their models, add new insights, and open new directions of research. Here, we review an integrated laboratory, field and modeling work conducted with subterranean rodents (Ctenomys sp.) living under an extreme pattern of natural daily light exposure. Tracking animal movement and light exposure with biologgers across seasons and performing laboratory experiments on running-wheel cages, we uncovered the mechanisms of day/night entrainment of the clock and of photoperiodic time measurement in this subterranean organism. We confirmed most of the features of Pittendrigh and Daan's models but highlighted the importance of integrating them with ecophysiological techniques, methodologies, and theories to get a full picture of the clock in the wild. This integration is essential to fully establish the importance of the temporal dimension in ecological studies and tackling relevant questions such as the role of the clock for all seasons in a changing planet. [ABSTRACT FROM AUTHOR]

Circadian clocks play an essential role in adapting locomotor activity as well as physiological, and metabolic rhythms of organisms to the day-night cycles on Earth during the four seasons. In addition, they can serve as a time reference for measuring day length and adapt organisms in advance to annual changes in the environment, which can be particularly pronounced at higher latitudes. The physiological responses of organisms to day length are also known as photoperiodism. This special issue of the Journal of Comparative Physiology A aims to account for diurnal and photoperiodic adaptations by presenting a collection of ten review articles, five original research articles, and three perspective pieces. The contributions include historical accounts, circadian and photoperiodic clock models, epigenetic, molecular, and neuronal mechanisms of seasonal adaptations, latitudinal differences in photoperiodic responses and studies in the wild that address the challenges of global change. [ABSTRACT FROM AUTHOR]

In 1936, Erwin Bünning published his groundbreaking work that the endogenous clock is used to measure day length for initiating photoperiodic responses. His publication triggered years of controversial debate until it ultimately became the basic axiom of rhythm research and the theoretical pillar of chronobiology. Bünning's thesis is frequently quoted in the articles in this special issue on the subject of "A clock for all seasons". However, nowadays only few people know in detail about Bünning's experiments and almost nobody knows about the contribution of his former doctoral student, Wolfgang Engelmann, to his theory because most work on this topic is published in German. The aim of this review is to give an overview of the most important experiments at that time, including Wolfgang Engelmann's doctoral thesis, in which he demonstrated the importance of the circadian clock for photoperiodic flower induction in the Flaming Katy, Kalanchoë blossfeldiana, but not in the Red Morning Glory, Ipomoea coccinea. [ABSTRACT FROM AUTHOR]

The circadian clock times physiological and behavioural processes and resets on a daily basis to synchronize with the environment. The involvement of the circadian clock in photoperiodic time measurement synchronising annual rhythms is still under debate and different models have been proposed explaining their integration. Insects overcome unfavourable conditions in diapause, a form of dormancy. A latitudinal cline in diapause induction in the parasitoid wasp Nasonia vitripennis as well as a difference in circadian light sensitivity between north and south provide us with additional evidence that the circadian system of Nasonia is involved in photoperiodic time measurement and that latitude-specific seasonality drives adaptive evolution in photoperiodism partly through adaptation responses in the circadian system. We tested diapause induction in a range of T-cycles and photoperiods and found diapause induction in short photoperiods in all T-cycles in the northern line but in the southern line, diapause only occurred in T-cycles close to 24 h. Due to a lower light sensitivity in the southern line, a wider distribution of phase angles of entrainment can be expected at a specific T-cycle duration, while the range of entrainment will decrease. Taking these oscillator properties into account, our data can be explained by an external coincidence model involving a single oscillator with a light-sensitive phase that drives annual timing of diapause in Nasonia vitripennis. [ABSTRACT FROM AUTHOR]

Seasonal adaptation in animals is a complex process that involves genetic, epigenetic, and environmental factors. The present review explores recent studies on epigenetic mechanisms implicated in seasonal adaptation in animals. The review is divided into three main sections, each focusing on a different epigenetic mechanism: DNA methylation, histone modifications, and non-coding RNA. Additionally, the review delves into the current understanding of how these epigenetic factors contribute to the regulation of circadian and seasonal cycles. Understanding these molecular mechanisms provides the first step in deciphering the complex interplay between genetics, epigenetics, and the environment in driving seasonal adaptation in animals. By exploring these mechanisms, a better understanding of how animals adapt to changing environmental conditions can be achieved. [ABSTRACT FROM AUTHOR]

David S. Saunders was an outstanding scientist, who devoted his life to his family and to insects. He has made many fundamental contributions to our understanding of how insects reproduce and adapt their reproduction and development to the seasonal changes on our planet. Most importantly, he was a pioneer in demonstrating the role of the circadian clock in insect photoperiodic time measurement, first in the jewel wasp Nasonia vitripennis, and later in varies species of flies. His books on biological rhythms and insect clocks are important undergraduate, graduate and research reference literature. David was also a brilliant teacher and mentor and played a major role in establishing and teaching a series of successful Erasmus-funded Chronobiology Summer Schools in Europe. He leaves behind a legacy, both professionally and personally. [ABSTRACT FROM AUTHOR]

The photoperiodic mechanism distinguishes between long and short days, and the circadian clock system is involved in this process. Although the necessity of circadian clock genes for photoperiodic responses has been demonstrated in many species, how the clock system contributes to photoperiodic mechanisms remains unclear. A comprehensive study, including the functional analysis of relevant genes and physiology of their expressing cells, is necessary to understand the molecular and cellular mechanisms. Since Drosophila melanogaster exhibits a shallow photoperiodism, photoperiodic mechanisms have been studied in non-model species, starting with brain microsurgery and neuroanatomy, followed by genetic manipulation in some insects. Here, we review and discuss the involvement of the circadian clock in photoperiodic mechanisms in terms of neural networks in insects. We also review recent advances in the neural mechanisms underlying photoperiodic responses in insects and snails, and additionally circadian clock systems in snails, whose involvement in photoperiodism has hardly been addressed yet. Brain neurosecretory cells, insulin-like peptide/diuretic hormone44-expressing pars intercerebralis neurones in the bean bug Riptortus pedestris and caudo-dorsal cell hormone-expressing caudo-dorsal cells in the snail Lymnaea stagnalis, both promote egg laying under long days, and their electrical excitability is attenuated under short and medium days, which reduces oviposition. The photoperiodic responses of the pars intercerebralis neurones are mediated by glutamate under the control of the clock gene period. Thus, we are now able to assess the photoperiodic response by neurosecretory cell activity to investigate the upstream mechanisms, that is, the photoperiodic clock and counter. [ABSTRACT FROM AUTHOR]

Numerous insect species living in temperate regions survive adverse conditions, such as winter, in a state of developmental arrest. The most reliable cue for anticipating seasonal changes is the day-to-night ratio, the photoperiod. The molecular mechanism of the photoperiodic timer in insects is mostly unclear. Multiple pieces of evidence suggest the involvement of circadian clock genes, however, their role might be independent of their well-established role in the daily oscillation of the circadian clock. Furthermore, reproductive diapause is preferentially studied in females, whereas males are usually used for circadian clock research. Given the idiosyncrasies of male and female physiology, we decided to test male reproductive diapause in a strongly photoperiodic species, the linden bug Pyrrhocoris apterus. The data indicate that reproduction is not under circadian control, whereas the photoperiod strongly determines males' mating capacity. Clock mutants in pigment dispersing factor and cryptochrome-m genes are reproductive even in short photoperiod. Thus, we provide additional evidence of the participation of circadian clock genes in the photoperiodic time measurement in insects. [ABSTRACT FROM AUTHOR]

Animals living at high latitudes are exposed to prominent seasonal changes to which they need to adapt to survive. By applying Zeitgeber cycles of different periods and photoperiods we show here that high-latitude D. ezoana flies possess evening oscillators and highly damped morning oscillators that help them adapting their activity rhythms to long photoperiods. In addition, the damped morning oscillators are involved in timing diapause. The flies measure night length and use external coincidence for timing diapause. We discuss the clock protein TIMELESS (d-TIM) as the molecular correlate and the small ventrolateral clock neurons (s-LNvs) as the anatomical correlates of the components measuring night length. [ABSTRACT FROM AUTHOR]

Wyeomyia smithii, the pitcher-plant mosquito, has evolved from south to north and from low to high elevations in eastern North America. Along this seasonal gradient, critical photoperiod has increased while apparent involvement of the circadian clock has declined in concert with the evolutionary divergence of populations. Response to classical experiments used to test for a circadian basis of photoperiodism varies as much within and among populations of W. smithii as have been found in the majority of all other insects and mites. The micro-evolutionary processes revealed within and among populations of W. smithii, programmed by a complex underlying genetic architecture, illustrate a gateway to the macro-evolutionary divergence of biological timing among species and higher taxa in general. [ABSTRACT FROM AUTHOR]

Diapause is a programmed stage-specific arrest or delay in reproduction or development and is commonly used to circumvent an adverse season. Some insect species exhibit maternal regulation of diapause, wherein environmental cues are perceived by the mother and subsequently determine the developmental fate of the offspring. Although maternal regulation of diapause is widespread, its endocrinological mechanisms remain largely unknown. In the band-legged ground cricket Dianemobius nigrofasciatus (Orthoptera: Trigonidiidae), embryonic diapause is maternally determined. Adult females under long-day conditions lay eggs that develop into nymphs without interruption, whereas those under short-day conditions lay diapause-destined eggs that arrest their development and enter diapause at a very early embryonic stage, the cellular blastoderm. How development is arrested at an early stage is a key area of interest. We hypothesized that juvenile hormone III (JH III) and 20-hydroxyecdysone (20E), the major insect hormones that regulate a wide variety of physiological processes, are involved not only in maternal decisions, but also in diapause entry in D. nigrofasciatus. The results showed that the hemolymph concentrations of JH III and 20E in adult females were lower under short-day conditions; however, the application of JH III and 20E to the mothers did not affect the diapause incidence of offspring. No differences were observed in the amounts of 20E between non-diapause and diapause-destined eggs, and JH III was not detected in these eggs. Thus, we found no evidence for the involvement of JH III and 20E in maternal decisions for embryonic diapause and diapause entry in D. nigrofasciatus. [ABSTRACT FROM AUTHOR]

We studied the humoral innate immune responsiveness (HII), i.e., the hemolysis of rabbit erythrocytes by complement proteins, the adaptive humoral (antibody production) immune responsiveness (AHI) to intraperitoneal injection of sheep red blood cells, the morphological and hormonal reproductive characteristics and stress level (blood cortisol) in male Campbell's hamsters kept under long-day (LD; 16D: 8N) and short-day (SD; 8D: 16N) photoperiods. In SD males we found the body mass, anogenital distance, midventral gland size, and level of testosterone in the peripheral blood (but not the cortisol level) decreased after two months of exposure. The results indicate lower HII, but not AHI in SD. Comparison of the SD nonresponders, SD responders, and LD individuals demonstrated a statistically significant increase of HII in SD photosensitive hamsters compared to LD. There was no link between HII and AHI, which indicates an independent photoperiodic responsiveness of different branches of the immune system. [ABSTRACT FROM AUTHOR]

Veronica nakaiana Ohwi is a Korean endemic species and has potential value as an ornamental and breeding resource of Veronica species. Therefore, it is necessary to determine the environmental factors for floral induction to manipulate flowering for the industrial application of this plant. This study was conducted to investigate the flowering response of V. nakaiana to cold temperatures and photoperiod treatments. In Expt. 1, six-week-old seedlings were treated with a cold temperature of 5 °C for from 0 to 12 weeks. After the artificial cold treatments, the plants were subjected to the following photoperiod treatments: 9/15, 12/12, 14/10, 16/8, or 24/0 (day/night) h. In Expt. 2, seven-month-old plants were transferred to an open field for natural cold treatments and the chilling hours were calculated to quantify the flowering response to cold temperatures. In Expt. 1, the photoperiod does not affect the percent flowering or flowering time. The plants flowered only after artificial cold treatments lasting for more than eight weeks. However, the average percent flowering was less than half. In Expt. 2, although flowering was also observed only after more than eight weeks of natural cold treatment, the percent flowering in Expt. 2 was higher than that in Expt. 1. In both experiments, the number of days to flowering significantly decreased with increasing the cold treatment period. These results indicated that V. nakaiana is a day-neutral plant and requires a prolonged period of cold temperatures. In addition, the cold requirement showed an age-dependent response on flowering. [ABSTRACT FROM AUTHOR]

The pond snail Lymnaea stagnalis exhibits clear photoperiodism in egg laying; it lays more eggs in long-day conditions than in medium-day conditions. A key regulator of egg laying is neurosecretory caudo-dorsal cells (CDCs) producing an ovulation hormone in the cerebral ganglia. Paired small budding structures of the cerebral ganglia (viz. the lateral lobe) also promote egg laying in addition to spermatogenesis and maturation of female accessory sex organs. However, it remains unknown which cells in the lateral lobe are responsible for these. Previous anatomical and physiological studies prompted us to hypothesize that canopy cells in the lateral lobe modulate activity of CDCs. However, double labeling of the canopy cell and CDCs revealed no sign of direct neural connections, suggesting that activity of CDCs is regulated either humorally or through a neural pathway independent of canopy cells. In addition, our detailed anatomical re-evaluation confirmed previous observations that the canopy cell bears fine neurites along the ipsilateral axon and extensions from the plasma membrane of the cell body, although the function of these extensions remains unexplored. Furthermore, comparison of electrophysiological properties between long-day and medium-day conditions indicated that the canopy cell's activity is moderately under photoperiodic regulation: resting membrane potentials of long-day snails are shallower than those of medium-day snails, and spontaneously spiking neurons are only observed in long-day conditions. Thus, canopy cells appear to receive photoperiodic information and regulate photoperiod-dependent phenomena, but not provide direct neural inputs to CDCs. [ABSTRACT FROM AUTHOR]

Understanding how endogenous and exogenous factors such as annual seasonal rhythm and photoperiodism affect pesticide toxicity is important to designing integrated pest management strategies. The two-spotted spider mite Tetranychus urticae Koch (Acari: Tetranychidae), a worldwide phytophagous pest species distributed across different zones with contrasting environmental conditions, is a good model for exploring how photoperiodism and seasonality affect their responses against pesticides. In this study, we conducted a laboratory experiment from March 2017 to November 2018 in which T. urticae populations were reared under three photoperiod regimes (10L:14D, 12L:12D, and 18L:6D) in environmentally controlled incubators, and assessed the toxicity of the two pesticides, diafenthiruon and propargite, on T. urticae every month. To determine potential mechanisms underlying the changes in pesticide toxicity, we measured body size and total GSTs activity of T. urticae along with the toxicity measurements in 2018. Our results showed that the photoperiod regime did not significantly affect the toxicity of each of the two pesticides to T. urticae. However, unlike photoperiodism, the toxicity of both pesticides was found to be season-dependent, being higher during spring and summer and lower during the winter. This suggests that seasonality could induce in those T. urticae populations, an endogenous mechanism that influenced their susceptibility to the tested pesticides. Pearson's correlation analyses showed that only the body size had a weak negative correlation with pesticide toxicity, thereby suggesting that pesticides could have higher toxicity on smaller T. urticae. Taken together, our study showed that seasonality can affect pesticide toxicity, thereby providing practical insights into the management strategies against T. urticae. [ABSTRACT FROM AUTHOR]

Photoperiod is a key environmental indicator for regulating embryonic development, individual growth and physiological processes in aquatic animals. In this study, differences in embryonic development and performance of newly hatched cuttlefish juvenile exposed to five different cycles of lightdark (L:D): constant light, 18L:6D, 12L:12D, 6L:18D cycles, and constant darkness were evaluated. Prolonged exposure to light induced an accelerated rate of embryonic development, particularly after the red-bead stage. Principal component analysis (PCA) revealed that red-bead stage, heartbeat, endoskeleton formation, pigment appear, and six increments of cuttlebone were the main factors contributing to the embryonic development. Meaning that the duration time of these five stages were significantly different when exposed to photoperiod regimes, which may determine the duration of the incubation period of the embryos. Long term light has also affected the incubation parameters with an increased rate in hatching and shortened the incubation and hatching periods in the 12–24-h day length range. However, constant light and darkness environment appeared to have a greater effect on the stress of embryonic development, mainly reflected in the yolk shed ratio and the inking rate in the egg capsule. Moreover, the increase in the day length has contributed to improve the growth and survival of juveniles in the 12–18-h day length range; however, juveniles exposed to constant light and darkness experienced worse results in terms of growth, tissue glycogen content, digestive enzymes of the digestive glands, and metabolic enzymes of the muscles. These finding suggest that prolonged light exposure accelerates the process of embryonic development, maximum feeding time is not necessarily a condition of optimal growth, and inappropriate light cycles can disturb the body's endogenous controls. Therefore, the optimal photoperiod for the embryos development and juvenile growth of Sepia pharaonis were 12 h and 12–18 h of day length, respectively. These results are useful for increasing the production of this species during embryo incubation and juveniles rearing in aquaculture practice. [ABSTRACT FROM AUTHOR]

Key message: Our findings suggest most wheat biological processes are under the control of the daily expressed genes. Plant circadian rhythms represent daily changes in the activity of various processes, which are based on changes in the levels of gene expression and protein synthesis. In wheat, some key components of plant circadian clock have been identified, but there is little data on the daily expression and interactions of these genes. To study the common wheat daily transcriptome, RNA sequencing was performed. Using these data, genes expressed in daily pattern and the metabolic pathways controlled by them were identified: responses to stimuli and nutrients, transport, photoperiodism, photomorphogenesis, synthesis and degradation of different metabolites, and regulation of the processes of RNA synthesis. It was shown that a significant part of the transcriptome can vary greatly daily. Five expression patterns were identified. They were characterized by peaks at different time points and described the genes underlying these patterns. The analysis of the enrichment of gene ontology terms with various patterns allowed us to describe the main metabolic pathways in each group. Wheat homologs of the genes related to circadian clock in Arabidopsis were identified. Most of them were represented by three homoeologous genes expressed uniformly. Comparison of their expression patterns demonstrated a shift in the expression peaks for some core and accessory genes; the majority of wheat circadian genes were expressed in accordance with Arabidopsis homologs. This may indicate a similar functional role of these genes in wheat. [ABSTRACT FROM AUTHOR]

Temporary water bodies, especially vernal pools, are the most sensitive aquatic environments to climate change yet the least studied. Their functioning largely depends on their phytoplankton community structure. This study aimed to determine how temperature and photoperiod length (by simulating inundation in different parts of the year under five climate scenarios) affect the succession and structure of phytoplankton communities soon after inundation. Photoperiod was the most important factor affecting phytoplankton species richness, total abundance and the abundance of taxonomic groups in the course of succession. A long photoperiod (16 h) and a moderate temperature (16 °C) in vernal pool microcosms (late spring inundation after a warm snowless winter) were the most favourable conditions for phytoplankton growth (especially for the main taxonomic groups: chlorophytes and cryptophytes) and species richness. With short photoperiods (inundation in winter) and low temperatures, the communities transformed towards diatoms, euglenoids and cyanobacteria. In line with our predictions, a high temperature (25 °C) favoured a decline in phytoplankton species diversity. Our study shows that climate change will result in seasonal shifts in species abundance or even in their disappearance and, finally, in potential strong changes in the biodiversity and food webs of aquatic ecosystems in the future. [ABSTRACT FROM AUTHOR]

Human cognitive functioning shows circadian variations throughout the day. However, individuals largely differ in their timing during the day of when they are more capable of performing specific tasks and when they prefer to sleep. These interindividual differences in preferred temporal organization of sleep and daytime activities define the chronotype. Since a late chronotype is associated with adverse mental and physical consequences, it is of vital importance to study how lighting environments affect chronotype. Here, we use a mathematical model of the human circadian pacemaker to understand how light in the built environment changes the chronotype distribution in the population. In line with experimental findings, we show that when individuals spend their days in relatively dim light conditions, this not only results in a later phase of their biological clock but also increases interindividual differences in circadian phase angle of entrainment and preferred sleep timing. Increasing daytime illuminance results in a more narrow distribution of sleep timing and circadian phase, and this effect is more pronounced for longer photoperiods. The model results demonstrate that modern lifestyle changes the chronotype distribution towards more eveningness and more extreme differences in eveningness. Such model-based predictions can be used to design guidelines for workplace lighting that help limiting circadian phase differences, and craft new lighting strategies that support human performance, health and wellbeing. [ABSTRACT FROM AUTHOR]

Photoperiod is a reliable cue to regulate growth and reproduction for seasonal adaptation. Although photoperiodism has been well studied in Chordata and Arthropoda, less is known about Mollusca. We examined photoperiodic effects on egg laying, body size, gonad-somatic index, oocyte size and relative amounts of caudodorsal cell hormone mRNA in individual rearing conditions in the pond snail Lymnaea stagnalis. Twenty-five weeks after hatching, the percentages of egg-laying snails under a photoperiod of 12 h light and 12 h darkness (12L:12D) were significantly smaller than those under longer days. The total numbers of eggs and egg masses under 12L:12D were significantly smaller than those under longer days. Significant differences between 16L:8D and 12L:12D were not observed in the soft body and ovotestis weight, and the gonad-somatic index. Photoperiodic effects were also not observed in oocyte diameters twenty-two weeks after hatching. Twenty-seven weeks after hatching amounts of caudodorsal cell hormone mRNA were significantly lower in the cerebral ganglia with commissure under 12L:12D than 16L:8D. L. stagnalis exhibited a clear photoperiodic response in egg laying and the amount of caudodorsal cell hormone mRNA, but not in gonadal development. Under 12L:12D suppression of caudodorsal cell hormone expression might suppress egg laying. [ABSTRACT FROM AUTHOR]

The bivoltine strain of the domestic silkworm, Bombyx mori, has two generations per year. It shows a facultative diapause phenotype determined by environmental conditions, including photoperiod and temperature, and nutrient conditions during embryonic and larval development of the mother. However, it remains unclear how the environmental signals received during development are selectively utilized as cues to determine alternative diapause phenotypes. We performed a comparative analysis between the Kosetsu strain of B. mori and a Japanese population of the wild mulberry silkworm B. mandarina concerning the hierarchical molecular mechanisms in diapause induction. Our results showed that for the Kosetsu, temperature signals during the mother's embryonic development predominantly affected diapause determination through the thermosensitive transient receptor potential ankyrin 1 (TRPA1) and diapause hormone (DH) signaling pathways. However, embryonic diapause in B. mandarina was photoperiod-dependent, although the DH signaling pathway and thermal sensitivity of TRPA1 were conserved within both species. Based on these findings, we hypothesize that TRPA1-activated signals are strongly linked to the signaling pathway participating in diapause induction in Kosetsu to selectively utilize the temperature information as the cue because temperature-dependent induction was replaced by photoperiodic induction in the TRPA1 knockout mutant. [ABSTRACT FROM AUTHOR]

The rising demand for spelt wheat (Triticum aestivum ssp. spelta) as a high-value grain crop has raised interest in its introduction into non-traditional spelt growing areas. This study aimed to assess adaptive constrains of spelt under short Mediterranean season. At first screening of a wide spelt collection for phenology and allelic distribution at the photoperiod (PPD) and vernalization (VRN) loci was done. In addition an in-depth phenotypic evaluation of a selected panel (n = 20) was performed, including agronomically important traits and concentration of grain mineral (GMC) and grain protein (GPC) content. Results from both wide screening and in-depth in panel (group of 18 spelt lines and two bread wheat lines) evaluation shows that the major adaptive constraint for spelt under Mediterranean conditions is late heading, caused by day length sensitivity, as evident from phenology and allelic profile (PPD and VRN). All lines carrying the photoperiod-sensitive allele (PPD-D1b) were late flowering (> 120DH). Based on the panel field evaluations those consequently suffer from low grain yield and poor agronomic performances. As for minerals, GMC for all but Zn, significantly correlated with GPC. In general, GMC negatively correlated with yield which complicated the assessment of GMC per-se and challenge the claim for higher mineral content in spelt grains. The exceptions were, Fe and Zn, which did not correlate with yield. Spelt lines showing high Fe and Zn concentration in a high-yield background illustrate their potential for spelt wheat breeding. Improving spelt adaptation to Mediterranean environments could be mediated by introducing the insensitive-PPD-D1a allele to spelt wheat background. Following this breeding path spelt could better compete with bread wheat under short season with limited and fluctuating rain fall. [ABSTRACT FROM AUTHOR]

In nature, photoperiod signals environmental seasonality and is a strong selective "zeitgeber" that synchronizes biological rhythms. For animals facing seasonal environmental challenges and energetic bottlenecks, daily torpor and hibernation are two metabolic strategies that can save energy. In the wild, the dwarf lemurs of Madagascar are obligate hibernators, hibernating between 3 and 7 months a year. In captivity, however, dwarf lemurs generally express torpor for periods far shorter than the hibernation season in Madagascar. We investigated whether fat-tailed dwarf lemurs (Cheirogaleus medius) housed at the Duke Lemur Center (DLC) could hibernate, by subjecting 8 individuals to husbandry conditions more in accord with those in Madagascar, including alternating photoperiods, low ambient temperatures, and food restriction. All dwarf lemurs displayed daily and multiday torpor bouts, including bouts lasting ~ 11 days. Ambient temperature was the greatest predictor of torpor bout duration, and food ingestion and night length also played a role. Unlike their wild counterparts, who rarely leave their hibernacula and do not feed during hibernation, DLC dwarf lemurs sporadically moved and ate. While demonstrating that captive dwarf lemurs are physiologically capable of hibernation, we argue that facilitating their hibernation serves both husbandry and research goals: first, it enables lemurs to express the biphasic phenotypes (fattening and fat depletion) that are characteristic of their wild conspecifics; second, by "renaturalizing" dwarf lemurs in captivity, they will emerge a better model for understanding both metabolic extremes in primates generally and metabolic disorders in humans specifically. [ABSTRACT FROM AUTHOR]

Although reference genes have previously been used in the expression analysis of genes involved in sugarcane flowering they had not been experimentally validated for stability and consistency of expression between different samples over a wide range of experimental conditions. Here we report the analysis of candidate reference genes in different tissue types, at different temporal time-points, in both short and long day photoperiodic treatments. The stability of the candidate reference genes in all conditions was evaluated with NormFinder, BestKeeper, and RefFinder algorithms that complement each other for a more robust analysis. As the Normfinder algorithm was more appropriate for our experimental conditions, greater emphasis was placed on Normfinder when choosing the most stable genes. UBQ1 and TUB were shown to be the most stable reference genes to use for normalizing RT-qPCR gene expression data during floral induction, whilst 25SrRNA1 and GAPDH were the least stable. Their use as a reference gene pair was validated by analyzing the expression of two differentially expressed target genes (PIL5 and LHP1). The UBQ1/TUB reference genes combination was able to reveal small significant differences in gene expression of the two target genes that were not detectable when using the least stable reference gene combination. These results can be used to inform the choice of reference genes to use in the study of the sugarcane floral induction pathway. Our work also demonstrates that both PIL5 and LHP1 are significantly up-regulated in the initial stages of photoperiodic induction of flowering in sugarcane. [ABSTRACT FROM AUTHOR]

The tortoise beetle, Laccoptera nepalensis Boheman (Coleoptera: Chrysomelidae), is an important insect pest of the sweet potato, and is naturally distributed in southern to eastern Asia. The species has recently been expanding its range to the main islands of Japan, where it had previously not been distributed. In this study, the life-history traits of a local population in southern Kyushu, Japan were examined. The adults showed a long-day photoperiodic response at 20 and 25 °C with critical photophases of 13.97 and 12.52 h/day, respectively: female adults reared under long-day conditions laid eggs, whereas those reared under short-day conditions did not and entered diapause. When adults that had been reared under 16L–8D at 20 °C were transferred to 12L–12D at 20 °C, they ceased laying eggs. These results, together with the developmental threshold temperature and thermal constant obtained for each stage, suggest that the beetle overwinters in the adult stage in a state of diapause and produces a maximum of three generations per year in southern Kyushu. [ABSTRACT FROM AUTHOR]

Earliness per se (Eps) genes are reported to be important in fine-tuning flowering time in wheat independently of photoperiod (Ppd) and vernalisation (Vrn). Unlike Ppd and Vrn genes, Eps have relatively small effects and their physiological effect along with chromosomal position are not well defined. We evaluated eight lines derived from crossing two vernalisation insensitive lines, Paragon and Baj (late and early flowering respectively), to study the detailed effects of two newly identified QTLs, Eps-7D and Eps-2B and their interactions under field conditions. The effect of both QTLs was minor and was affected by the allelic status of the other. While the magnitude of effect of these QTLs on anthesis was similar, they are associated with very different profiles of pre-anthesis development which also depends on their interaction. Eps-7D affected both duration before and after terminal spikelet while not affecting final leaf number (FLN) so Eps-7D-early had a faster rate of leaf appearance. Eps-2B acted more specifically in the early reproductive phase and slightly altered FLN without affecting the leaf appearance rate. Both QTLs affected the spike fertility by altering the rate of floret development and mortality. The effect of Eps-2B was very small but consistent in that -late allele tended to produce more fertile florets. [ABSTRACT FROM AUTHOR]

At high latitudes, approximately 10% of people suffer from depression during the winter season, a phenomenon known as seasonal affective disorder (SAD). Shortened photoperiod and/or light intensity during winter season are risk factors for SAD, and bright light therapy is an effective treatment. Interestingly, reduced retinal photosensitivity along with the mood is observed in SAD patients in winter. However, the molecular basis underlying seasonal changes in retinal photosensitivity remains unclear, and pharmacological intervention is required. Here we show photoperiodic regulation of dopamine signaling and improvement of short day–attenuated photosensitivity by its pharmacological intervention in mice. Electroretinograms revealed dynamic seasonal changes in retinal photosensitivity. Transcriptome analysis identified short day-mediated suppression of the Th gene, which encodes tyrosine hydroxylase, a rate-limiting enzyme for dopamine biosynthesis. Furthermore, pharmacological intervention in dopamine signaling through activation of the cAMP signaling pathway rescued short day–attenuated photosensitivity, whereas dopamine receptor antagonists decreased photosensitivity under long-day conditions. Our results reveal molecular basis of seasonal changes in retinal photosensitivity in mammals. In addition, our findings provide important insights into the pathogenesis of SAD and offer potential therapeutic interventions. [ABSTRACT FROM AUTHOR]

Coconut palm has two distinct types—"tall" and "dwarf"—which differ morphologically. Tall coconut varieties need 8–10 years to start flowering, while dwarf coconut varieties only require 3–5 years. We compared seedling and reproductive stage transcriptomes for both coconut types to determine potential molecular mechanisms underlying control of flowering time in coconut. Several key genes in the photoperiod pathway were differentially expressed between seedling and reproductive leaf samples in both tall and dwarf coconut. These genes included suppressor of overexpression of constans (SOC1), flowering locus T (FT), and Apetala 1 (AP1). Alternative splicing analysis of genes in the photoperiod pathway further revealed that the FT gene produces different transcripts in tall compared to dwarf coconut. The shorter alternative splice variant of FT [which included a 6 bp deletion, alternative 3′ splicing sites (A3SS)] was found to be exclusively present in dwarf coconut varieties but absent in most tall coconut varieties. Our results provide a valuable information resource as well as suggesting a probable mechanism for differentiation of flowering time onset in coconut, providing a target for future breeding work in accelerating time to flowering in this crop species. [ABSTRACT FROM AUTHOR]

Carrot (Daucus carota L.) is a biennial plant requiring vernalization to induce flowering, but long days can promote its premature bolting and flowering. The basic genetic network controlling the flowering time has been constructed for carrot, but there is limited information on the molecular mechanisms underlying the photoperiodic flowering response. The published carrot genome could provide an effective tool for systematically retrieving the key integrator genes of GIGANTEA (GI), CONSTANS-LIKE (COL), FLOWERING LOCUS T (FT), and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) homologues in the photoperiod pathway. In this study, the bolting time of wild species "Songzi" (Ws) could be regulated by different photoperiods, but the orange cultivar "Amsterdam forcing" (Af) displayed no bolting phenomenon. According to the carrot genome and previous de novo transcriptome, 1 DcGI, 15 DcCOLs, 2 DcFTs, and 3 DcSOC1s were identified in the photoperiod pathway. The circadian rhythm peaks of DcGI, DcCOL2, DcCOL5a, and DcCOL13b could be delayed under long days (LDs). The peak value of DcCOL2 in Af (12.9) was significantly higher than that in Ws (6.8) under short day (SD) conditions, and was reduced under LD conditions (5.0). The peak values of DcCOL5a in Ws were constantly higher than those in Af under the photoperiod treatments. The expression levels of DcFT1 in Ws (463.0) were significantly upregulated under LD conditions compared with those in Af (1.4). These responses of DcCOL2, DcCOL5a, and DcFT1 might be related to the different bolting responses of Ws and Af. This study could provide valuable insights into understanding the key integrator genes in the carrot photoperiod pathway. [ABSTRACT FROM AUTHOR]

Photoperiodism has been shown to be an important synchronizer of seasonal reproduction in many rodent species in the wild; it is a reliable cue as in the southern hemisphere it coincides with the onset of rainfall and hence the availability of food resources for maximal reproductive success. The photoperiodic effect on the reproductive status of the Namibian gerbil, Gerbilliscus cf. leucogaster from central Namibia was investigated. Twenty adult males were exposed to a long-day length (16L:8D), while further 20 adult males were subjected to a short-day length (SD:8L:16D); all for a period of 3 months. Testicular mass per gram body mass, testicular volume and seminiferous tubule diameters were used to assess the effect of photoperiod on gonadal development. Body mass did not significantly differ between the two photoperiodic regimes. The testicular mass per gram of body mass was significantly heavier for the males maintained on a long photoperiod compared to those on a short photoperiod. Similarly, testicular volume and seminiferous tubule diameter were greater in males maintained on a long-day cycle compared to those on the short-day cycle. These findings suggest that G. cf. leucogaster is photoresponsive to day length changes. Photoperiodic changes in the semi-arid habitats can be used to herald the onset of reproduction as it often acts in concert with other proximate cues in desert rodents, but is a constant environmental cue that does not change from year to year, unlike rainfall patterns. [ABSTRACT FROM AUTHOR]

Understanding how phenotypic traits vary among populations inhabiting different environments is critical for predicting a species' vulnerability to climate change. Yet, little is known about the key functional traits that determine the distribution of populations and the main mechanisms—phenotypic plasticity vs. local adaptation—underlying intraspecific functional trait variation. Using the Asian burying beetle Nicrophorus nepalensis, we demonstrate that mountain ranges differing in elevation and latitude offer unique thermal environments in which two functional traits—thermal tolerance and reproductive photoperiodism—interact to shape breeding phenology. We show that populations on different mountain ranges maintain similar thermal tolerances, but differ in reproductive photoperiodism. Through common garden and reciprocal transplant experiments, we confirm that reproductive photoperiodism is locally adapted and not phenotypically plastic. Accordingly, year-round breeding populations on mountains of intermediate elevation are likely to be most susceptible to future warming because maladaptation occurs when beetles try to breed at warmer temperatures. Understanding whether intraspecific trait variation results from local adaptation or phenotypic plasticity is crucial to predict species responses to climate change. Here the authors investigate geographically distinct burying beetle populations, showing that photoperiodism is a locally adapted, not phenotypically plastic, trait. [ABSTRACT FROM AUTHOR]

Main conclusion: Photoacclimation to variable light and photoperiod regimes in C. vulgaris represents a complex interplay between "biogenic" phytochrome-mediated sensing and "operational" redox sensing signaling pathways.Chlorella vulgaris Beijerinck UTEX 265 exhibits a yellow-green phenotype when grown under high light (HL) in contrast to a dark green phenotype when grown at low light (LL). The redox state of the photosynthetic electron transport chain (PETC) as estimated by excitation pressure has been proposed to govern this phenotypic response. We hypothesized that if the redox state of the PETC was the sole regulator of the HL phenotype, C. vulgaris should photoacclimate in response to the steady-state excitation pressure during the light period regardless of the length of the photoperiod. As expected, LL-grown cells exhibited a dark green phenotype, low excitation pressure (1 − qP = 0.22 ± 0.02), high chlorophyll (Chl) content (375 ± 77 fg Chl/cell), low Chl a/b ratio (2.97 ± 0.18) as well as high photosynthetic efficiency and photosynthetic capacity regardless of the photoperiod. In contrast, C. vulgaris grown under continuous HL developed a yellow-green phenotype characterized by high excitation pressure (1 − qP = 0.68 ± 0.01), a relatively low Chl content (180 ± 53 fg Chl/cell), high Chl a/b ratio (6.36 ± 0.54) with concomitantly reduced light-harvesting polypeptide abundance, as well as low photosynthetic capacity and efficiency measured on a per cell basis. Although cells grown under HL and an 18 h photoperiod developed a typical yellow-green phenotype, cells grown at HL but a 12 h photoperiod exhibited a dark green phenotype comparable to LL-grown cells despite exhibiting growth under high excitation pressure (1 − qP = 0.80 ± 0.04). The apparent uncoupling of excitation pressure and phenotype in HL-grown cells and a 12 h photoperiod indicates that chloroplast redox status cannot be the sole regulator of photoacclimation in C. vulgaris. We conclude that photoacclimation in C. vulgaris to HL is dependent upon growth history and reflects a complex interaction of endogenous systems that sense changes in photoperiod as well as photosynthetic redox balance. [ABSTRACT FROM AUTHOR]

Invasive pentatomid Halyomorpha halys recently arrived to the Black Sea region and began damaging agricultural and ornamental plants. We studied the effects of day length and temperature on the pre-adult development and diapause induction in H. halys from Sochi (Russia) under laboratory conditions (20, 24, and 28 °C and several photoperiods). The pre-adult development of H. halys was noticeably faster under L:D 12:12 compared with L:D 15:9. The sum of effective temperatures required for the pre-adult development was ca. 530 and 590 degree days under these two conditions, respectively, whereas the lower developmental thresholds were similar (ca. 13.3 °C). Adults of H. halys demonstrated a typical long-day-type photoperiodic response of facultative winter adult diapause induction: Short days (photophases of 12-15 h) induced diapause in all adults, whereas long days (with photophases longer than 15 h) promoted reproduction. The photoperiodic responses of diapause induction of females and males were very similar. At 24 °C, the threshold of the response was between 15 and 16 h. At 20 °C, even under the very long-day conditions (L:D 18:6) about 50% of adults entered diapause. Field records suggest that H. halys likely produces two generations per year in Sochi. Short days might accelerate nymphal growth of the second generation in August and then induce winter diapause in adults. Phenological studies and monitoring are needed for a better understanding of the adaptation process of this invasive pest to new conditions. [ABSTRACT FROM AUTHOR]

Early in the 20th century, disparate human developmental processes culminate excess artificial light during night time and distort the phenological, physiological and ecological responses, which are sustained in the plants, animals and microorganism from millions of years. Earlier studies regarding artificial light (AL) during the night predominantly covered the drastic effects on animal systems. Although, drastic effects of AL during night time are enormous; therefore, the present topic is focused on the physiological and ecological consequences of artificial night light pollution (ANLP) on plant systems. In these consequences, most of the plant processes under ANLP are affected intensely and cause compelling changes in plant life cycle from germination to maturity. However, severe effects were observed in the case of pollination, photoreceptor signalling, flowering and microhabitats of plants. Along with drastic effects on ecology and environments, its relevance to human developmental processes cannot be avoided. Therefore, we need to equipoise between sustainable environment and steadily human development processes. Further, selection of plant/crop species, which are more responsive to ANLP, can minimize the ecological consequences of night light pollution. Likewise, changing artificial nightscape with the implication of new LEDs (Light Emitting Diodes) lightening policies like UJALA (www.ujala.gov.in), which are low cost, more durable, eco-friendly and less emitter of CO2, have potential to overcome the biodiversity threats, which arise due to old artificial lightening technology from decades. Hence, adopting new advance artificial lightening technology and understanding its impact on plant ecosystem will be a future challenge for plant biologist. [ABSTRACT FROM AUTHOR]

Worldwide, there is a dramatic decline in freshwater eel populations (Anguilla spp.), resulting in an urgent need to improve eel management and artificial reproduction protocols. Unfortunately, eels in captivity do not reproduce spontaneously as they remain in a (pre)-pubertal state resulting from a strong neural blockage. Eel propagation is possible to some extent by applying extensive, expensive, unnatural hormonal treatments. However, the success rates are still far too low to support a sustainable farming industry, due to low gamete quality and low survival rates of larvae. Artificial reproduction of eels has been pursued for almost 80 years, and maturation protocols have changed little. In order to improve current protocols it is clear that a different approach towards stimulating sexual maturation is required. In many fish species, changes in external environmental cues, such as photoperiod and temperature, are crucial to induce gonadal recrudescence and development. Still, the natural triggers involved in the gametogenesis of eels are poorly understood. The time-keeping hormone melatonin is a well-known transmitter of external cues, and influences various physiological processes, including reproduction. In eels, we hypothesize that melatonin is an important key player in the regulation of sexual maturation. Thus far, its mode of action is still an area which needs to be explored. In this review, we provide an overview of the current knowledge of studied natural cues possibly affecting reproductive function and the plausible role of melatonin in the regulation of puberty in eels. [ABSTRACT FROM AUTHOR]

The effects of alien substitutions of chromosomes on the heading time of ditelosomic (DT) wheat-barley substitution lines in which the chromosome 7HLmar from Hordeum marinum ssp. gussoneanum 4x replaced the chromosomes 7A, 7B and 7D of common wheat were studied. The plants were grown under short and long day illumination in greenhouse and in the field. The lines studied were found to differ in response to the length of the day. Under short day conditions, DT7HLmar(7B) and DT7HLmar(7A) showed an increase in the period before heading. In this case, the substitution effect of chromosome 7B was more significant than the effect of chromosome 7A. Under these conditions, the substitution of chromosome 7D did not have a significant effect on the heading time. Under long day conditions in the greenhouse and under natural conditions of a long day in the Novosibirsk region, substitution lines came into ear earlier than under a short day conditions and did not differ in the heading time. Allele-specific primers established the allelic composition of the genes Vrn-A1, Vrn-B1, Vrn-D1 and Vrn-B3 in ditelosomic lines. It was shown that the two DT7HLmar(7A) and DT7HLmar(7D) lines have the same genotype -VRN-A1b/VRN-B1c/vrn-D1/vrn-B3 and that the DT7HLmar(7B) line has the genotype -VRN-A1a/VRN-B1c/vrn-D1. The results show that regardless of the genotype for the Vrn genes, the wheat-barley substitution lines react to the change in the photoperiod, especially in the absence of chromosomes 7B and 7A. [ABSTRACT FROM AUTHOR]

Polygonia c-aureum females exhibit photoperiodically induced imaginal diapause, characterized by cessation of ovarian development. Females grown at a short daylength (SD) entered imaginal diapause, whereas those grown at a long daylength (LD) produced eggs rapidly after adult emergence at 21 °C. The termination of diapause was influenced by daylength: diapause ended faster at LD than SD. Complete termination of diapause took 30 days in unchilled females reared under LD at 21 °C. On the other hand, prompt, synchronized and strong diapause termination occurred at post-chilling periods. Photoperiods at post-chilling periods affected ovarian development, when the length of pre-chilling periods or the length of chilling periods was shorter, suggesting that these treatments were not enough to complete diapause development. Ovarian development proceeded earlier in chilled and subsequent warmed females than unchilled females. Wing damage was remarkable at post-chilling periods when females were reared under an adequate length of pre-chilling and chilling periods, especially comparing with females under pre-overwintering conditions without chilling, indicating that post-diapause reproductive development was weak in unchilled females. Thus, exposure to low temperatures is necessary for a strong diapause termination in this butterfly. [ABSTRACT FROM AUTHOR]

Biennial plants perceived seasonal stimuli through the photoperiods and vernalization pathways respectively to optimize developmental time. Photoperiods combining with vernalization modulate hormone homeostasis to promote plant normally growth. IAA and ABA play important roles in plant development. Although a series of IAA and ABA genes and their regulation mechanisms have been investigated and characterized extensively in model plants, these underlined mechanisms in Beta vulgaris L. especially under abiotic stress were not entirely clear. This study aimed at exploring IAA and ABA biosynthetic pathway genes and investigating their expression patterns and quantitating analysis hormone by UPLC-MS/MS (ultra performance liquid chromatography-tandem mass spectrometry) in order to demonstrate the molecular mechanism of phytohormone in B. vulgaris. As the results showed BvNIT4 and BvIAA8 contributed to IAA accumulation under nonvernalization condition. Endogenous ABA accumulation in leaves was contributed coordinately by the expression of BvABA2 and BvNCED1 genes both in the vernalized and nonvernalized samples under long day conditions. Vernalization and photoperiods indeed disturb phytohormone genes expression patterns, which data were consistent with the previous studies. New insight was provided to further clarify the molecular mechanism of endogenous hormone in B. vulgaris. [ABSTRACT FROM AUTHOR]

This study provides new and practical information to implement the use of photoperiodic manipulation for the control of the sexual maturation of Canadian 6+ Atlantic wolffish (Anarhichas lupus) and 3+ first-time spawners spotted wolffish (Anarhichas minor) from Canadian and Norwegian populations. Wolffish reproductive cycle (gametogenesis and oocyte maturation and spermiation) was monitored for 23 consecutive months. Control groups were held under a 12-month simulated natural photoperiod and treatment groups under an 8-month compressed photoperiod. Plasma sex steroid concentrations (estradiol-17β and 11-ketotestosterone), oocyte diameter growth, and milt production were assessed monthly. For all groups under study, fish subjected to the compressed photoperiod spawned 2-6 months earlier than the controls. Complete out-of-shift cycle was not achieved based on the completion of two reproduction cycles, and this is briefly discussed. Photoperiod treatment induced temporal shifts in sex steroid profiles, which are the likely mediators of altered timing of ovulation/final maturation. Photoperiod has a strong influence on the timing of wolffish maturation and could be used as an efficient and inexpensive tool to secure wolffish reproduction operations (year-round supply of egg and milt and/or timing with optimal temperature regimes). [ABSTRACT FROM AUTHOR]

We studied the effects of temperature on the photoperiodic regulation of seasonal reproduction and related events in the subtropical tree sparrow at Shillong, India. In the first experiment, one group of birds was maintained in an outdoor open aviary receiving natural photoperiod and temperature conditions, while the other group was exposed to natural photoperiod and constant temperature of 17 ± 2 °C in an outdoor closed aviary for 12 months. Although both sexes achieved peak gonadal growth at the same time (May) under the two conditions, gonadal regression and feathers molt were delayed under the temperature controlled condition. In the second experiment, the groups of birds were exposed to three different temperatures (17, 25 and 30 °C) under both long (LD-14L:10D) and short (SD-9L:15D) day lengths for 7 months. Birds showed relatively small but significant gonadal growth, darkening of bill color and feathers molt only at 30 °C under SD. However, they behaved as though they were under natural conditions and exhibited the above responses significantly at all temperatures under LD. There was delayed gonadal regression at the lower temperature (17 °C), while feathers molt delayed with increasing temperature (25, 30 °C) under LD. These results clearly indicate that temperature modulates photoperiodic seasonal responses in the tree sparrow. [ABSTRACT FROM AUTHOR]

Adelphocoris triannulatus (Stål) (Heteroptera: Miridae) is a zoophytophagous bug that inhabits grasslands and crop fields, and is widely distributed in eastern Asia. In this study, the seasonal occurrence and environmental factors controlling the seasonal life cycle of this bug were investigated in a local population in southern Kyushu, Japan. When insects were reared under different photoperiods at 20 and 25 °C, they produced diapause or nondiapause eggs depending on the photoperiod: when reared under short-day photoperiods (≤ 13 h/day), females laid diapause eggs, whereas they laid nondiapause eggs when reared under long-day photoperiods (≥ 14 h/day). Because the developmental duration of the pre-adult stages and maturation (minimum duration of one generation) is estimated to be approximately 30 days at summer temperatures, these results suggest that this bug has a multivoltine seasonal life cycle. In agreement with the laboratory results, only nondiapause eggs were produced until mid-August in the field, and an increasing proportion of diapause eggs were produced from early September. In addition to these findings, field sampling from spring to autumn in 2009 indicated that three or four generations were produced in one year. These results suggest that egg diapause plays a role in preventing nymphs of A. triannulatus from developing in winter, and thereby ensures the survival of the population in adverse seasons. [ABSTRACT FROM AUTHOR]

Day length has been shown to be a major source of temporal information regulating seasonal reproduction in the Eurasian tree sparrow (Passer montanus). The present study aims to investigate the photoperiodic expression of gonadotropin-releasing hormone-I (GnRH-I), and how it mediates seasonal reproduction in male tree sparrows. In different experiments, we studied photoperiod-induced changes in GnRH-I expressing neurons in the hypothalamic preoptic area (POA), together with changes in testicular size under both natural and artificial photoperiodic conditions. Experiment 1, which involved studying changes in GnRH-I expression and testicular volume during different phases of the annual reproductive cycle under natural day length (NDL), revealed that sparrows possess a definite seasonal cycle of GnRH-I peptide expression that runs parallel to testicular size. Birds showed significantly higher levels of GnRH-I expression in the breeding phase when compared to the non-breeding phase. In experiment 2, photosensitive birds were exposed to artificial short (SD: 9L/15D) and long (LD: 14L/10D) day lengths for 240 days to investigate the photoperiodic regulation of GnRH-I expression. They exhibited a significant increase followed by a decrease in GnRH-I expression and testicular size under LD but not SD, suggesting photoperiodic regulation. In experiment 3, when photosensitive birds were exposed to increasing photoperiods (9L/15D, 10L/14D, 10.5L/13.5D, 11L/13D, 12L/12D) for 30 days to find out the critical photoperiod for GnRH-I expression, they responded only when the daily photoperiod was 11 h or more. These results clearly indicate that tree sparrows are capable of fine discrimination of photoperiodic information and use day length for GnRH-I expression to control their seasonal reproduction. [ABSTRACT FROM AUTHOR]

We have investigated the role of the thermo-photoperiodic condition of maternal generation in diapause induction of Trichogramma chilonis (Ishii) (Hymenoptera: Trichogrammatidae) lab strain. To test the maternal effect, two lines of T. chilonis lab strain were generated by rearing them for one generation at: (1) 15 °C with L:D-12:12 (15F-112) and (2) 15 °C with L:D-20:4 (15F-120). The laboratory strain reared at 15 °C with L:D-12:12 for 65 generations (15F-6512) was used as the control (acclimatized strain) due to its proven diapausing capacity. The 15F-120 line failed to undergo diapause, though healthy pre-pupae were formed at the pre-storage condition (at 10 °C with L:D- 8:16 and RH-60-70%). However, 15F-112 line could successfully complete all the phases of diapause and was comparable with the control batch. Considering 50% adult emergence and minimum 3 days of longevity, 125 days of storage could be achieved. From our current study, we conclude that diapause can be induced in T. chilonis lab strain by providing appropriate thermo-photoperiod to their maternal generation (for a single generation) followed by suitable diapause inducing and terminating protocols. [ABSTRACT FROM AUTHOR]

Seasonal affective disorder (SAD), beyond mood changes, is characterized by alterations in daily rhythms of behavior and physiology. The pathophysiological conditions of SAD involve changes in day length and its first-line treatment is bright light therapy. Animal models using nocturnal rodents have been studied to elucidate the neurobiological mechanisms of depression, but might be ill suited to study the therapeutic effects of light in SAD since they exhibit light-aversive responses. Here Arvicanthis ansorgei, a diurnal rodent, was used to determine behavioral, molecular and brain dopamine changes in response to exposure to a winter-like photoperiod consisting of a light-dark cycle with 8 h of light, under diminished light intensity, and 16 h of darkness. Furthermore, we evaluated whether timed-daily bright light exposure has an effect on behavior and brain physiology of winter-like exposed animals. Arvicanthis under a winter-like condition showed alterations in the synchronization of the locomotor activity rhythm to the light-dark cycle. Moreover, alterations in day-night activity of dopaminergic neurotransmission were revealed in the nucleus accumbens and the dorsal striatum, and in the day-night clock gene expression in the suprachiasmatic nucleus. Interestingly, whereas dopamine disturbances were reversed in animals exposed to daily light at early or late day, altered phase of the daily rhythm of locomotion was reverted only in animals exposed to light at the late day. Moreover, Per2 gene expression in the SCN was also affected by light exposure at late day in winter-like exposed animals. These findings suggest that light induces effects on behavior by mechanisms that rely on both circadian and rhythm-independent pathways influencing the dopaminergic circuitry. This last point might be crucial for understanding the mechanisms of non-pharmacological treatment in SAD. [ABSTRACT FROM AUTHOR]

Andean Potato is a major crop for farmers in the Andes and represents an important gene pool for potato improvement. We present the population structure and genetic diversity of 88 Andigena accessions collected in Northwestern Argentina based on functional markers (25 SSR) distributed along 12 chromosomes. Polymorphic information content ranged from 0.40 to 0.87. A Bayesian approach, a Principal Coordinate Analysis and a Cluster Analysis revealed the presence of: I) a major group containing most of the Andean accessions and II) a smaller group including the out-group cv. Spunta and the sequenced genotype DM. Several group specific alleles were detected. AMOVA showed that 81% of the variability was within each group. Eleven of the SSRs analyzed are linked or within genes reported to regulate traits of nutritional and industrial interest. Additionally, the allelic variant of a photoperiod dependent tuberization regulator gene, StCDF1.2, was exclusively detected in accessions clustered in group II. [ABSTRACT FROM AUTHOR]

Photoperiod and food availability often interact in the regulation of reproductive development in seasonal environments. We tested the effects of a 10% food restriction and short- (SD) and long-day (LD) photoperiods on reproductive preparedness of male spiny mice ( Acomys spinosissimus ) from South Africa. Males were either fed ad libitum or a 10% restricted diet and on both food regimes, they were exposed to either a 14 h light:10 h dark (LD) or 10 h light:14 h dark (SD) photoperiod. Testes size, seminiferous tubule diameter and faecal androgen metabolite (fAM) concentrations were larger in food restricted males subjected to LD than in any of the other groups. SD photoperiods did not suppress reproductive development, despite earlier findings, which may be explained by “spontaneous” recrudescence due to prolonged exposure to SD. The increased development of the gonads and higher fAM concentrations observed in food restricted LD males may indicate a terminal investment strategy in male spiny mice with males investing more into reproduction in the face of reduced future survival. [ABSTRACT FROM AUTHOR]

Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is one of the most serious pests of tomato, capable of causing 100% crop losses under favourable conditions. We studied the effect of different host plants on developmental and population parameters of this pest at 25 ± 0.5 °C temperature, 70 ± 5% relative humidity and 12 L: 12D photoperiod. Host plant had significant effect on the developmental biology and the population growth parameters of the pest. The leafminer developed fastest on tomato leaves and slowest on potato tubers. Population growth parameters like intrinsic rate of increase, net reproductive rate, finite rate of increase, doubling time and weekly multiplication rate of T. absoluta were highest on tomato leaves and lowest on potato tubers. Mean generation time was minimum on tomato leaves and maximum on potato tubers. Females developed on tomato leaves were more fecund than other hosts. Though, tomato was found to be the most suitable host plant of T. absoluta, yet, the pest developed and grew successfully on other alternate hosts like potato (Solanum tuberosum L.), brinjal (Solanum melongena L.) and pepino (Solanum muricatum Aiton). These hosts can, therefore, play an important role in the survival, population build up and overwintering of the miner. Further, under favourable conditions the miner can become a serious pest on these crops and need to be monitored on these crops as well. [ABSTRACT FROM AUTHOR]

Abstract Clock‐regulated pathways coordinate the response of many developmental processes to changes in photoperiod and temperature. We model two of the best‐understood clock output pathways in Arabidopsis, which control key regulators of flowering and elongation growth. In flowering, the model predicted regulatory links from the clock to CYCLING DOF FACTOR 1 (CDF1) and FLAVIN‐BINDING, KELCH REPEAT, F‐BOX 1 (FKF1) transcription. Physical interaction data support these links, which create threefold feed‐forward motifs from two clock components to the floral regulator FT. In hypocotyl growth, the model described clock‐regulated transcription of PHYTOCHROME‐INTERACTING FACTOR 4 and 5 (PIF4, PIF5), interacting with post‐translational regulation of PIF proteins by phytochrome B (phyB) and other light‐activated pathways. The model predicted bimodal and end‐of‐day PIF activity profiles that are observed across hundreds of PIF‐regulated target genes. In the response to temperature, warmth‐enhanced PIF4 activity explained the observed hypocotyl growth dynamics but additional, temperature‐dependent regulators were implicated in the flowering response. Integrating these two pathways with the clock model highlights the molecular mechanisms that coordinate plant development across changing conditions.