RESUMO
Circadian clocks are important for an individual's fitness, and recent studies have underlined their role in the outcome of biological interactions. However, the relevance of circadian clocks in fungal-fungal interactions remains largely unexplored. We sought to characterize a functional clock in the biocontrol agent Trichoderma atroviride to assess its importance in the mycoparasitic interaction against the phytopathogen Botrytis cinerea. Thus, we confirmed the existence of circadian rhythms in T. atroviride, which are temperature-compensated and modulated by environmental cues such as light and temperature. Nevertheless, the presence of such molecular rhythms appears to be highly dependent on the nutritional composition of the media. Complementation of a clock null (Δfrq) Neurospora crassa strain with the T. atroviride-negative clock component (tafrq) restored core clock function, with the same period observed in the latter fungus, confirming the role of tafrq as a bona fide core clock component. Confrontation assays between wild-type and clock mutant strains of T. atroviride and B. cinerea, in constant light or darkness, revealed an inhibitory effect of light on T. atroviride's mycoparasitic capabilities. Interestingly, when confrontation assays were performed under light/dark cycles, T. atroviride's overgrowth capacity was enhanced when inoculations were at dawn compared to dusk. Deleting the core clock-negative element FRQ in B. cinerea, but not in T. atroviride, was vital for the daily differential phenotype, suggesting that the B. cinerea clock has a more significant influence on the result of this interaction. Additionally, we observed that T. atroviride clock components largely modulate development and secondary metabolism in this fungus, including the rhythmic production of distinct volatile organic compounds (VOCs). Thus, this study provides evidence on how clock components impact diverse aspects of T. atroviride lifestyle and how daily changes modulate fungal interactions and dynamics.
Assuntos
Botrytis , Proteínas CLOCK , Ritmo Circadiano , Proteínas Fúngicas , Hypocreales , Interações Microbianas , Metabolismo Secundário , Botrytis/crescimento & desenvolvimento , Botrytis/metabolismo , Botrytis/efeitos da radiação , Proteínas CLOCK/metabolismo , Ritmo Circadiano/efeitos da radiação , Proteínas Fúngicas/metabolismo , Hypocreales/crescimento & desenvolvimento , Hypocreales/metabolismo , Hypocreales/efeitos da radiação , Luz , TemperaturaRESUMO
Coastal habitats, in particular sandy beaches, are becoming increasingly exposed to artificial light pollution at night (ALAN). Yet, only a few studies have this far assessed the effects of ALAN on the species inhabiting these ecosystems. In this study we assessed the effects of ALAN on Tylos spinulosus, a prominent wrack-consumer isopod living in sandy beaches of north-central Chile. This species burrows in the sand during daylight and emerges at night to migrate down-shore, so we argue it can be used as a model species for the study of ALAN effects on coastal nocturnal species. We assessed whether ALAN alters the distribution and locomotor activity of this isopod using a light system placed in upper shore sediments close to the edge of the dunes, mimicking light intensities measured near public lighting. The response of the isopods was compared to control transects located farther away and not exposed to artificial light. In parallel, we measured the isopods' locomotor activity in the laboratory using actographs that recorded their movement within mesocosms simulating the beach surface. Measurements in the field indicated a clear reduction in isopod abundance near the source of the light and a restriction of their tidal distribution range, as compared to control transects. Meanwhile, the laboratory experiments showed that in mesocosms exposed to ALAN, isopods exhibited reduced activity and a circadian rhythm that was altered and even lost after a few days. Such changes with respect to control mesocosms with a natural day/night cycle suggest that the changes observed in the field were directly related to a disruption in the locomotor activity of the isopods. All together these results provide causal evidence of negative ALAN effects on this species, and call for further research on other nocturnal sandy beach species that might become increasingly affected by ALAN.
Assuntos
Ritmo Circadiano/efeitos da radiação , Poluição Ambiental/efeitos adversos , Isópodes/fisiologia , Iluminação/efeitos adversos , Locomoção/efeitos da radiação , Animais , Chile , EcossistemaRESUMO
Artificial lab manipulation of LD cycles has enabled simulations of the disruptive conditions found in modern human societies, such as jet-lag, night-work and light at night. New techniques using animal models have been developed, and these can greatly improve our understanding of circadian disruption. Some of these techniques, such as in vivo bioluminescence assays, require minimum external light. This requirement is challenging because the usual lighting protocols applied in circadian desynchronization experiments rely on considerable light input. Here, we present a novel LD regimen that can disrupt circadian rhythms with little light per day, based on computer simulations of a model limit-cycle oscillator. The model predicts that a single light pulse per day has the potential to disturb rhythmicity when pulse times are randomly distributed within an interval. Counterintuitively, the rhythm still preserves an underlying 24-h periodicity when this interval is as large as 14 h, indicating that day/night cues are still detectable. Only when pulses are spread throughout the whole 24-h day does the rhythm lose any day-to-day period correlation. In addition, the model also reveals that stronger pulses of brighter light should exacerbate the disrupting effects. We propose the use of this LD schedule-which would be compatible with the requirements of in vivo bioluminescence assays-to help understand circadian disruption and associated illnesses.
Assuntos
Ritmo Circadiano/efeitos da radiação , Luz , Iluminação , Modelos Teóricos , Fotoperíodo , Animais , Simulação por Computador , Humanos , Síndrome do Jet Lag , Jornada de Trabalho em TurnosRESUMO
This study investigated the effect of using an artificial bright light on the entrainment of the sleep/wake cycle as well as the reaction times of athletes before the Rio 2016 Olympic Games. A total of 22 athletes from the Brazilian Olympic Swimming Team were evaluated, with the aim of preparing them to compete at a time when they would normally be about to go to bed for the night. During the 8-day acclimatization period, their sleep/wake cycles were assessed by actigraphy, with all the athletes being treated with artificial light therapy for between 30 and 45 min (starting at day 3). In addition, other recommendations to improve sleep hygiene were made to the athletes. In order to assess reaction times, the Psychomotor Vigilance Test was performed before (day 1) and after (day 8) the bright light therapy. As a result of the intervention, the athletes slept later on the third (p = 0.01), seventh (p = 0.01) and eighth (p = 0.01) days after starting bright light therapy. Regarding reaction times, when tested in the morning the athletes showed improved average (p = 0.01) and minimum reaction time (p = 0.03) when comparing day 8 to day 1. When tested in the evening, they showed improved average (p = 0.04), minimum (p = 0.03) and maximum reaction time (p = 0.02) when comparing day 8 to day 1. Light therapy treatment delayed the sleep/wake cycles and improved reaction times of members of the swimming team. The use of bright light therapy was shown to be effective in modulating the sleep/wake cycles of athletes who had to perform in competitions that took place late at night.
Assuntos
Ciclos de Atividade/efeitos da radiação , Atletas/psicologia , Ritmo Circadiano/efeitos da radiação , Comportamento Competitivo , Fototerapia/métodos , Tempo de Reação/efeitos da radiação , Sono/efeitos da radiação , Natação , Vigília/efeitos da radiação , Adulto , Feminino , Humanos , Masculino , Fatores de Tempo , Resultado do Tratamento , Adulto JovemRESUMO
The non-visual opsin, melanopsin, expressed in the mammalian retina, is considered a circadian photopigment because it is responsible to entrain the endogenous biological clock. This photopigment is also present in the melanophores of Xenopus laevis, where it was first described, but its role in these cells is not fully understood. X. laevis melanophores respond to light with melanin granule dispersion, the maximal response being achieved at the wavelength of melanopsin maximal excitation. Pigment dispersion can also be triggered by endothelin-3 (ET-3). Here we show that melanin translocation is greater when a blue light pulse was applied in the presence of ET-3. In addition, we demonstrated that mRNA levels of the melanopsins Opn4x and Opn4m exhibit temporal variation in melanophores under light/dark (LD) cycles or constant darkness, suggesting that this variation is clock-driven. Moreover, under LD cycles the oscillations of both melanopsins show a circadian profile suggesting a role for these opsins in the photoentrainment mechanism. Blue-light pulse decreased Opn4x expression, but had no effect on Opn4m. ET-3 abolishes the circadian rhythm of expression of both opsins; in addition the hormone increases Opn4x expression in a dose-, circadian time- and light-dependent way. ET-3 also increases the expression of its own receptor, in a dose-dependent manner. The variation of melanopsin levels may represent an adaptive mechanism to ensure greater melanophore sensitivity in response to environmental light conditions with ideal magnitude in terms of melanin granule dispersion, and consequently color change.
Assuntos
Ritmo Circadiano/efeitos dos fármacos , Ritmo Circadiano/fisiologia , Endotelinas/farmacologia , Opsinas de Bastonetes/metabolismo , Animais , Ritmo Circadiano/efeitos da radiação , Luz , Melaninas/metabolismo , Melanóforos/citologia , Melanóforos/efeitos dos fármacos , Melanóforos/metabolismo , Melanóforos/efeitos da radiação , Fotoperíodo , Receptores de Endotelina/genética , Receptores de Endotelina/metabolismo , Xenopus laevisRESUMO
UNLABELLED: Systemic low doses of the endotoxin lipopolysaccharide (LPS, 100 µg/kg) administered during the early night induce phase-delays of locomotor activity rhythms in mice. Our aim was to evaluate the role of tumor necrosis factor (Tnf)-alpha and its receptor 1/p55 (Tnfr1) in the modulation of LPS-induced circadian effects on the suprachiasmatic nucleus (SCN). We observed that Tnfr1-defective mice (Tnfr1 KO), although exhibiting similar circadian behavior and light response to that of control mice, did not show LPS-induced phase-delays of locomotor activity rhythms, nor LPS-induced cFos and Per2 expression in the SCN and Per1 expression in the paraventricular hypothalamic nucleus (PVN) as compared to wild-type (WT) mice. We also analyzed Tnfr1 expression in the SCN of WT mice, peaking during the early night, when LPS has a circadian effect. Peripheral inoculation of LPS induced an increase in cytokine/chemokine levels (Tnf, Il-6 and Ccl2) in the SCN and in the PVN. In conclusion, in this study, we show that LPS-induced circadian responses are mediated by Tnf. Our results also suggest that this cytokine stimulates the SCN after LPS peripheral inoculation; and the time-related effect of LPS (i.e. phase shifts elicited only at early night) might depend on the increased levels of Tnfr1 expression. We also confirmed that LPS modulates clock gene expression in the SCN and PVN in WT but not in Tnfr1 KO mice. HIGHLIGHTS: We demonstrate a fundamental role for Tnf and its receptor in circadian modulation by immune stimuli at the level of the SCN biological clock.
Assuntos
Relógios Biológicos , Ritmo Circadiano , Atividade Motora , Transdução de Sinais , Núcleo Supraquiasmático/metabolismo , Fator de Necrose Tumoral alfa/metabolismo , Animais , Relógios Biológicos/efeitos dos fármacos , Relógios Biológicos/efeitos da radiação , Quimiocina CCL2/metabolismo , Ritmo Circadiano/efeitos dos fármacos , Ritmo Circadiano/efeitos da radiação , Esquema de Medicação , Interleucina-6/metabolismo , Luz , Lipopolissacarídeos/administração & dosagem , Masculino , Camundongos Endogâmicos C57BL , Camundongos Knockout , Atividade Motora/efeitos dos fármacos , Atividade Motora/efeitos da radiação , Núcleo Hipotalâmico Paraventricular/metabolismo , Fotoperíodo , Receptores Tipo I de Fatores de Necrose Tumoral/deficiência , Receptores Tipo I de Fatores de Necrose Tumoral/genética , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/efeitos da radiação , Núcleo Supraquiasmático/efeitos dos fármacos , Núcleo Supraquiasmático/efeitos da radiação , Fatores de TempoRESUMO
Disruption of the maternal environment during pregnancy is a key contributor to offspring diseases that develop in adult life. To explore the impact of chronodisruption during pregnancy in primates, we exposed pregnant capuchin monkeys to constant light (eliminating the maternal melatonin rhythm) from the last third of gestation to term. Maternal temperature and activity circadian rhythms were assessed as well as the newborn temperature rhythm. Additionally we studied the effect of daily maternal melatonin replacement during pregnancy on these rhythms. Ten pregnant capuchin monkeys were exposed to constant light from 60% of gestation to term. Five received a daily oral dose of melatonin (250 µg kg/body weight) at 1800 h (LL+Mel) and the other five a placebo (LL). Six additional pregnant females were maintained in a 14â¶10 light:dark cycles and their newborns were used as controls (LD). Rhythms were recorded 96 h before delivery in the mother and at 4-6 days of age in the newborn. Exposure to constant light had no effect on the maternal body temperature rhythm however it delayed the acrophase of the activity rhythm. Neither rhythm was affected by melatonin replacement. In contrast, maternal exposure to constant light affected the newborn body temperature rhythm. This rhythm was entrained in control newborns whereas LL newborns showed a random distribution of the acrophases over 24-h. In addition, mean temperature was decreased (34.0±0.6 vs 36.1±0.2°C, in LL and control, respectively P<0.05). Maternal melatonin replacement during pregnancy re-synchronized the acrophases and restored mean temperature to the values in control newborns. Our findings demonstrate that prenatal melatonin is a Zeitgeber for the newborn temperature rhythm and supports normal body temperature maintenance. Altogether these prenatal melatonin effects highlight the physiological importance of the maternal melatonin rhythm during pregnancy for the newborn primate.
Assuntos
Ritmo Circadiano/efeitos da radiação , Luz , Mães , Temperatura , Animais , Animais Recém-Nascidos , Comportamento Animal/efeitos dos fármacos , Comportamento Animal/fisiologia , Comportamento Animal/efeitos da radiação , Cebus , Ritmo Circadiano/efeitos dos fármacos , Feminino , Masculino , Exposição Materna/efeitos adversos , Melatonina/farmacologia , Gravidez , Terceiro Trimestre da Gravidez/efeitos dos fármacos , Terceiro Trimestre da Gravidez/fisiologia , Terceiro Trimestre da Gravidez/efeitos da radiação , Fatores de TempoRESUMO
OBJECTIVE: To evaluate the serum melatonin levels in critically ill pediatric patients and to test the effect of light on the melatonin's circadian rhythm. Data on melatonin secretion in critically ill pediatric subjects are lacking. STUDY DESIGN: We investigated the serum melatonin levels of 16 sedated and mechanically ventilated patients in a pediatric intensive care unit. Children (mean age, 5.1 ± 3.1 years) were randomly assigned to a dark-exposed or to a light-exposed group to evaluate the effects of light on serum melatonin concentrations. Blood samples for serum melatonin analysis were collected at 10 p.m., 1 a.m., 3 a.m., 5 a.m., 8 a.m., and 12 p.m. RESULTS: The melatonin circadian rhythm was severely disrupted in critically ill children; light exposure lowered serum melatonin even in a context of highly altered circadian cycle; melatonin peaks were greater for healthy age-matched children. CONCLUSION: The high melatonin levels in the critically ill children may be a response to counteract the elevated oxidative stress associated with serious diseases. Whether these elevated melatonin levels confer any beneficial effects in pediatric critically ill patients remains unknown.
Assuntos
Ritmo Circadiano/efeitos da radiação , Estado Terminal , Luz , Melatonina/sangue , Pré-Escolar , Feminino , Humanos , Masculino , Projetos Piloto , Estudos Prospectivos , Fatores de TempoRESUMO
Surprisingly, in our modern 24/7 society, there is scant information on the impact of developmental chronodisruption like the one experienced by shift worker pregnant women on fetal and postnatal physiology. There are important differences between the maternal and fetal circadian systems; for instance, the suprachiasmatic nucleus is the master clock in the mother but not in the fetus. Despite this, several tissues/organs display circadian oscillations in the fetus. Our hypothesis is that the maternal plasma melatonin rhythm drives the fetal circadian system, which in turn relies this information to other fetal tissues through corticosterone rhythmic signaling. The present data show that suppression of the maternal plasma melatonin circadian rhythm, secondary to exposure of pregnant rats to constant light along the second half of gestation, had several effects on fetal development. First, it induced intrauterine growth retardation. Second, in the fetal adrenal in vivo it markedly affected the mRNA expression level of clock genes and clock-controlled genes as well as it lowered the content and precluded the rhythm of corticosterone. Third, an altered in vitro fetal adrenal response to ACTH of both, corticosterone production and relative expression of clock genes and steroidogenic genes was observed. All these changes were reversed when the mother received a daily dose of melatonin during the subjective night; supporting a role of melatonin on overall fetal development and pointing to it as a 'time giver' for the fetal adrenal gland. Thus, the present results collectively support that the maternal circadian rhythm of melatonin is a key signal for the generation and/or synchronization of the circadian rhythms in the fetal adrenal gland. In turn, low levels and lack of a circadian rhythm of fetal corticosterone may be responsible of fetal growth restriction; potentially inducing long term effects in the offspring, possibility that warrants further research.
Assuntos
Glândulas Suprarrenais/embriologia , Relógios Circadianos/efeitos dos fármacos , Relógios Circadianos/efeitos da radiação , Feto/fisiologia , Luz/efeitos adversos , Melatonina/farmacologia , Mães , Fatores de Transcrição ARNTL/genética , Glândulas Suprarrenais/efeitos dos fármacos , Glândulas Suprarrenais/fisiologia , Glândulas Suprarrenais/efeitos da radiação , Hormônio Adrenocorticotrópico/farmacologia , Animais , Ritmo Circadiano/efeitos dos fármacos , Ritmo Circadiano/efeitos da radiação , Corticosterona/sangue , Proteína 1 de Resposta de Crescimento Precoce/genética , Feminino , Feto/efeitos dos fármacos , Feto/embriologia , Feto/efeitos da radiação , Regulação da Expressão Gênica no Desenvolvimento/efeitos dos fármacos , Regulação da Expressão Gênica no Desenvolvimento/efeitos da radiação , Proteínas Circadianas Period/genética , Fosfoproteínas/genética , Gravidez , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Ratos , Ratos Sprague-Dawley , Receptores de Melatonina/genética , Fatores de TempoRESUMO
We investigated the diurnal dependence of the hypocotyl-growth responses to shade under sunlight-night cycles in Arabidopsis thaliana. Afternoon shade events promoted hypocotyl growth, while morning shade was ineffective. The lhy-D, elf3, lux, pif4 pif5, toc1, and quadruple della mutants retained the response to afternoon shade and the lack of response to morning shade while the lhy cca1 mutant responded to both morning and afternoon shade. The phyB mutant, plants overexpressing the multidrug resistance-like membrane protein ABCB19, and the iaa17/axr3 loss-of-function mutant failed to respond to shade. Transient exposure of sunlight-grown seedlings to synthetic auxin in the afternoon caused a stronger promotion of hypocotyl growth than morning treatments. The promotion of hypocotyl growth by afternoon shade or afternoon auxin required light perceived by phytochrome A or cryptochromes during the previous hours of the photoperiod. Although the ELF4-ELF3-LUX complex, PIF4, PIF5, and DELLA are key players in the generation of diurnal hypocotyl-growth patterns, they exert a minor role in the control of the diurnal pattern of growth responses to shade. We conclude that the strong diurnal dependency of hypocotyl-growth responses to shade relates to the balance between the antagonistic actions of LHY-CCA1 and a light-derived signal.