RESUMEN
Efficient generation of germinal center (GC) responses requires directed movement of B cells between distinct microenvironments underpinned by specialized B cell-interacting reticular cells (BRCs). How BRCs are reprogrammed to cater to the developing GC remains unclear, and studying this process is largely hindered by incomplete resolution of the cellular composition of the B cell follicle. Here we used genetic targeting of Cxcl13-expressing cells to define the molecular identity of the BRC landscape. Single-cell transcriptomic analysis revealed that BRC subset specification was predetermined in the primary B cell follicle. Further topological remodeling of light and dark zone follicular dendritic cells required CXCL12-dependent crosstalk with B cells and dictated GC output by retaining B cells in the follicle and steering their interaction with follicular helper T cells. Together, our results reveal that poised BRC-defined microenvironments establish a feed-forward system that determines the efficacy of the GC reaction.
Asunto(s)
Oscuridad , Células Dendríticas Foliculares/inmunología , Células Dendríticas Foliculares/metabolismo , Centro Germinal/inmunología , Centro Germinal/metabolismo , Inmunomodulación/efectos de la radiación , Luz , Animales , Linfocitos B/inmunología , Linfocitos B/metabolismo , Biomarcadores , Comunicación Celular , Quimiocina CXCL12/metabolismo , Ratones , Ratones Transgénicos , Fenotipo , Análisis de la Célula Individual , Subgrupos de Linfocitos T/inmunología , Subgrupos de Linfocitos T/metabolismoRESUMEN
Overnight fires are emerging in North America with previously unknown drivers and implications. This notable phenomenon challenges the traditional understanding of the 'active day, quiet night' model of the diurnal fire cycle1-3 and current fire management practices4,5. Here we demonstrate that drought conditions promote overnight burning, which is a key mechanism fostering large active fires. We examined the hourly diurnal cycle of 23,557 fires and identified 1,095 overnight burning events (OBEs, each defined as a night when a fire burned through the night) in North America during 2017-2020 using geostationary satellite data and terrestrial fire records. A total of 99% of OBEs were associated with large fires (>1,000 ha) and at least one OBE was identified in 20% of these large fires. OBEs were early onset after ignition and OBE frequency was positively correlated with fire size. Although warming is weakening the climatological barrier to night-time fires6, we found that the main driver of recent OBEs in large fires was the accumulated fuel dryness and availability (that is, drought conditions), which tended to lead to consecutive OBEs in a single wildfire for several days and even weeks. Critically, we show that daytime drought indicators can predict whether an OBE will occur the following night, which could facilitate early detection and management of night-time fires. We also observed increases in fire weather conditions conducive to OBEs over recent decades, suggesting an accelerated disruption of the diurnal fire cycle.
Asunto(s)
Oscuridad , Sequías , Incendios Forestales , Sequías/estadística & datos numéricos , Ecosistema , América del Norte , Incendios Forestales/estadística & datos numéricosRESUMEN
The medial entorhinal cortex (MEC) hosts many of the brain's circuit elements for spatial navigation and episodic memory, operations that require neural activity to be organized across long durations of experience1. Whereas location is known to be encoded by spatially tuned cell types in this brain region2,3, little is known about how the activity of entorhinal cells is tied together over time at behaviourally relevant time scales, in the second-to-minute regime. Here we show that MEC neuronal activity has the capacity to be organized into ultraslow oscillations, with periods ranging from tens of seconds to minutes. During these oscillations, the activity is further organized into periodic sequences. Oscillatory sequences manifested while mice ran at free pace on a rotating wheel in darkness, with no change in location or running direction and no scheduled rewards. The sequences involved nearly the entire cell population, and transcended epochs of immobility. Similar sequences were not observed in neighbouring parasubiculum or in visual cortex. Ultraslow oscillatory sequences in MEC may have the potential to couple neurons and circuits across extended time scales and serve as a template for new sequence formation during navigation and episodic memory formation.
Asunto(s)
Corteza Entorrinal , Neuronas , Periodicidad , Animales , Ratones , Corteza Entorrinal/citología , Corteza Entorrinal/fisiología , Neuronas/fisiología , Giro Parahipocampal/fisiología , Carrera/fisiología , Factores de Tiempo , Oscuridad , Corteza Visual/fisiología , Vías Nerviosas , Navegación Espacial/fisiología , Memoria EpisódicaRESUMEN
Changes in the amount of daylight (photoperiod) alter physiology and behaviour1,2. Adaptive responses to seasonal photoperiods are vital to all organisms-dysregulation associates with disease, including affective disorders3 and metabolic syndromes4. The circadian rhythm circuitry is implicated in such responses5,6, yet little is known about the precise cellular substrates that underlie phase synchronization to photoperiod change. Here we identify a brain circuit and system of axon branch-specific and reversible neurotransmitter deployment that are critical for behavioural and sleep adaptation to photoperiod. A type of neuron called mrEn1-Pet17 in the mouse brainstem median raphe nucleus segregates serotonin from VGLUT3 (also known as SLC17A8, a proxy for glutamate) to different axonal branches that innervate specific brain regions involved in circadian rhythm and sleep-wake timing8,9. This branch-specific neurotransmitter deployment did not distinguish between daylight and dark phase; however, it reorganized with change in photoperiod. Axonal boutons, but not cell soma, changed neurochemical phenotype upon a shift away from equinox light/dark conditions, and these changes were reversed upon return to equinox conditions. When we genetically disabled Vglut3 in mrEn1-Pet1 neurons, sleep-wake periods, voluntary activity and clock gene expression did not synchronize to the new photoperiod or were delayed. Combining intersectional rabies virus tracing and projection-specific neuronal silencing, we delineated a preoptic area-to-mrEn1Pet1 connection that was responsible for decoding the photoperiodic inputs, driving the neurotransmitter reorganization and promoting behavioural synchronization. Our results reveal a brain circuit and periodic, branch-specific neurotransmitter deployment that regulates organismal adaptation to photoperiod change.
Asunto(s)
Adaptación Fisiológica , Axones , Ritmo Circadiano , Neurotransmisores , Fotoperiodo , Animales , Femenino , Ratones , Adaptación Fisiológica/fisiología , Sistemas de Transporte de Aminoácidos Acídicos/deficiencia , Sistemas de Transporte de Aminoácidos Acídicos/genética , Sistemas de Transporte de Aminoácidos Acídicos/metabolismo , Axones/metabolismo , Axones/fisiología , Ritmo Circadiano/fisiología , Proteínas CLOCK/genética , Oscuridad , Núcleo Dorsal del Rafe/citología , Núcleo Dorsal del Rafe/metabolismo , Vías Nerviosas/fisiología , Neurotransmisores/metabolismo , Área Preóptica/citología , Área Preóptica/metabolismo , Terminales Presinápticos/metabolismo , Terminales Presinápticos/fisiología , Virus de la Rabia , Serotonina/metabolismo , Sueño/fisiología , Vigilia/fisiologíaRESUMEN
Night-time provides a critical window for slowing or extinguishing fires owing to the lower temperature and the lower vapour pressure deficit (VPD). However, fire danger is most often assessed based on daytime conditions1,2, capturing what promotes fire spread rather than what impedes fire. Although it is well appreciated that changing daytime weather conditions are exacerbating fire, potential changes in night-time conditions-and their associated role as fire reducers-are less understood. Here we show that night-time fire intensity has increased, which is linked to hotter and drier nights. Our findings are based on global satellite observations of daytime and night-time fire detections and corresponding hourly climate data, from which we determine landcover-specific thresholds of VPD (VPDt), below which fire detections are very rare (less than 95 per cent modelled chance). Globally, daily minimum VPD increased by 25 per cent from 1979 to 2020. Across burnable lands, the annual number of flammable night-time hours-when VPD exceeds VPDt-increased by 110 hours, allowing five additional nights when flammability never ceases. Across nearly one-fifth of burnable lands, flammable nights increased by at least one week across this period. Globally, night fires have become 7.2 per cent more intense from 2003 to 2020, measured via a satellite record. These results reinforce the lack of night-time relief that wildfire suppression teams have experienced in recent years. We expect that continued night-time warming owing to anthropogenic climate change will promote more intense, longer-lasting and larger fires.
Asunto(s)
Oscuridad , Calentamiento Global , Incendios Forestales , Calentamiento Global/estadística & datos numéricos , Tiempo (Meteorología) , Incendios Forestales/prevención & control , Incendios Forestales/estadística & datos numéricosRESUMEN
To increase computational flexibility, the processing of sensory inputs changes with behavioural context. In the visual system, active behavioural states characterized by motor activity and pupil dilation1,2 enhance sensory responses, but typically leave the preferred stimuli of neurons unchanged2-9. Here we find that behavioural state also modulates stimulus selectivity in the mouse visual cortex in the context of coloured natural scenes. Using population imaging in behaving mice, pharmacology and deep neural network modelling, we identified a rapid shift in colour selectivity towards ultraviolet stimuli during an active behavioural state. This was exclusively caused by state-dependent pupil dilation, which resulted in a dynamic switch from rod to cone photoreceptors, thereby extending their role beyond night and day vision. The change in tuning facilitated the decoding of ethological stimuli, such as aerial predators against the twilight sky10. For decades, studies in neuroscience and cognitive science have used pupil dilation as an indirect measure of brain state. Our data suggest that, in addition, state-dependent pupil dilation itself tunes visual representations to behavioural demands by differentially recruiting rods and cones on fast timescales.
Asunto(s)
Color , Pupila , Reflejo Pupilar , Visión Ocular , Corteza Visual , Animales , Oscuridad , Aprendizaje Profundo , Ratones , Estimulación Luminosa , Pupila/fisiología , Pupila/efectos de la radiación , Reflejo Pupilar/fisiología , Células Fotorreceptoras Retinianas Conos/efectos de los fármacos , Células Fotorreceptoras Retinianas Conos/fisiología , Células Fotorreceptoras Retinianas Bastones/efectos de los fármacos , Células Fotorreceptoras Retinianas Bastones/fisiología , Factores de Tiempo , Rayos Ultravioleta , Visión Ocular/fisiología , Corteza Visual/fisiologíaRESUMEN
Time-restricted feeding (TRF) has recently gained interest as a potential anti-ageing treatment for organisms from Drosophila to humans1-5. TRF restricts food intake to specific hours of the day. Because TRF controls the timing of feeding, rather than nutrient or caloric content, TRF has been hypothesized to depend on circadian-regulated functions; the underlying molecular mechanisms of its effects remain unclear. Here, to exploit the genetic tools and well-characterized ageing markers of Drosophila, we developed an intermittent TRF (iTRF) dietary regimen that robustly extended fly lifespan and delayed the onset of ageing markers in the muscles and gut. We found that iTRF enhanced circadian-regulated transcription and that iTRF-mediated lifespan extension required both circadian regulation and autophagy, a conserved longevity pathway. Night-specific induction of autophagy was both necessary and sufficient to extend lifespan on an ad libitum diet and also prevented further iTRF-mediated lifespan extension. By contrast, day-specific induction of autophagy did not extend lifespan. Thus, these results identify circadian-regulated autophagy as a critical contributor to iTRF-mediated health benefits in Drosophila. Because both circadian regulation and autophagy are highly conserved processes in human ageing, this work highlights the possibility that behavioural or pharmaceutical interventions that stimulate circadian-regulated autophagy might provide people with similar health benefits, such as delayed ageing and lifespan extension.
Asunto(s)
Autofagia/fisiología , Ritmo Circadiano/fisiología , Drosophila melanogaster/fisiología , Conducta Alimentaria/fisiología , Longevidad/fisiología , Envejecimiento/genética , Envejecimiento/efectos de la radiación , Animales , Autofagia/genética , Biomarcadores , Relojes Circadianos/efectos de la radiación , Ritmo Circadiano/genética , Ritmo Circadiano/efectos de la radiación , Oscuridad , Drosophila melanogaster/genética , Drosophila melanogaster/efectos de la radiación , Conducta Alimentaria/efectos de la radiación , Femenino , Longevidad/genética , Longevidad/efectos de la radiación , Masculino , Factores de TiempoRESUMEN
Light makes carbon fixation possible, allowing plant and animal life on Earth. We have previously shown that light regulates alternative splicing in plants. Light initiates a chloroplast retrograde signaling that regulates nuclear alternative splicing of a subset of Arabidopsis thaliana transcripts. Here, we show that light promotes RNA polymerase II (Pol II) elongation in the affected genes, whereas in darkness, elongation is lower. These changes in transcription are consistent with elongation causing the observed changes in alternative splicing, as revealed by different drug treatments and genetic evidence. The light control of splicing and elongation is abolished in an Arabidopsis mutant defective in the transcription factor IIS (TFIIS). We report that the chloroplast control of nuclear alternative splicing in plants responds to the kinetic coupling mechanism found in mammalian cells, providing unique evidence that coupling is important for a whole organism to respond to environmental cues.
Asunto(s)
Empalme Alternativo/efectos de la radiación , Arabidopsis/efectos de la radiación , Regulación de la Expresión Génica de las Plantas/efectos de la radiación , Luz , Plantas Modificadas Genéticamente/efectos de la radiación , ARN de Planta/efectos de la radiación , Elongación de la Transcripción Genética/efectos de la radiación , Acetilación , Arabidopsis/genética , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Oscuridad , Histonas/genética , Histonas/metabolismo , Cinética , Mutación , Plantas Modificadas Genéticamente/genética , Plantas Modificadas Genéticamente/metabolismo , ARN Polimerasa II/genética , ARN Polimerasa II/metabolismo , ARN de Planta/biosíntesis , ARN de Planta/genética , Factores de Elongación Transcripcional/genética , Factores de Elongación Transcripcional/metabolismoRESUMEN
Congenital stationary night blindness (CSNB) is an inherited retinal disease that causes a profound loss of rod sensitivity without severe retinal degeneration. One well-studied rhodopsin point mutant, G90D-Rho, is thought to cause CSNB because of its constitutive activity in darkness causing rod desensitization. However, the nature of this constitutive activity and its precise molecular source have not been resolved for almost 30 y. In this study, we made a knock-in (KI) mouse line with a very low expression of G90D-Rho (equal in amount to ~0.1% of normal rhodopsin, WT-Rho, in WT rods), with the remaining WT-Rho replaced by REY-Rho, a mutant with a very low efficiency of activating transducin due to a charge reversal of the highly conserved ERY motif to REY. We observed two kinds of constitutive noise: one being spontaneous isomerization (R*) of G90D-Rho at a molecular rate (R* s-1) 175-fold higher than WT-Rho and the other being G90D-Rho-generated dark continuous noise comprising low-amplitude unitary events occurring at a very high molecular rate equivalent in effect to ~40,000-fold of R* s-1 from WT-Rho. Neither noise type originated from G90D-Opsin because exogenous 11-cis-retinal had no effect. Extrapolating the above observations at low (0.1%) expression of G90D-Rho to normal disease exhibited by a KI mouse model with RhoG90D/WTand RhoG90D/G90D genotypes predicts the disease condition very well quantitatively. Overall, the continuous noise from G90D-Rho therefore predominates, constituting the major equivalent background light causing rod desensitization in CSNB.
Asunto(s)
Enfermedades Hereditarias del Ojo , Enfermedades Genéticas Ligadas al Cromosoma X , Miopía , Ceguera Nocturna , Rodopsina , Animales , Ceguera Nocturna/genética , Ceguera Nocturna/metabolismo , Enfermedades Hereditarias del Ojo/genética , Enfermedades Hereditarias del Ojo/metabolismo , Ratones , Rodopsina/genética , Rodopsina/metabolismo , Enfermedades Genéticas Ligadas al Cromosoma X/genética , Enfermedades Genéticas Ligadas al Cromosoma X/metabolismo , Miopía/genética , Miopía/metabolismo , Células Fotorreceptoras Retinianas Bastones/metabolismo , Células Fotorreceptoras Retinianas Bastones/patología , Oscuridad , Transducina/genética , Transducina/metabolismo , Técnicas de Sustitución del Gen , Modelos Animales de EnfermedadRESUMEN
Plant lipids are important as alternative sources of carbon and energy when sugars or starch are limited. Here, we applied combined heat and darkness or extended darkness to a panel of â¼300 Arabidopsis (Arabidopsis thaliana) accessions to study lipid remodeling under carbon starvation. Natural allelic variation at 3-KETOACYL-COENZYME A SYNTHASE4 (KCS4), a gene encoding an enzyme involved in very long chain fatty acid (VLCFA) synthesis, underlies the differential accumulation of polyunsaturated triacylglycerols (puTAGs) under stress. Ectopic expression of KCS4 in yeast and plants proved that KCS4 is a functional enzyme localized in the endoplasmic reticulum with specificity for C22 and C24 saturated acyl-CoA. Allelic mutants and transient overexpression in planta revealed the differential role of KCS4 alleles in VLCFA synthesis and leaf wax coverage, puTAG accumulation, and biomass. Moreover, the region harboring KCS4 is under high selective pressure and allelic variation at KCS4 correlates with environmental parameters from the locales of Arabidopsis accessions. Our results provide evidence that KCS4 plays a decisive role in the subsequent fate of fatty acids released from chloroplast membrane lipids under carbon starvation. This work sheds light on both plant response mechanisms and the evolutionary events shaping the lipidome under carbon starvation.
Asunto(s)
Proteínas de Arabidopsis , Arabidopsis , Humanos , Arabidopsis/metabolismo , Coenzima A/genética , Coenzima A/metabolismo , Oscuridad , Amigos , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Ácidos Grasos/metabolismo , Triglicéridos/metabolismo , Regulación de la Expresión Génica de las PlantasRESUMEN
Germinated plants grow in darkness until they emerge above the soil. To help the seedling penetrate the soil, most dicot seedlings develop an etiolated apical structure consisting of an apical hook and folded, unexpanded cotyledons atop a rapidly elongating hypocotyl. Brassinosteroids (BRs) are necessary for etiolated apical development, but their precise role and mechanisms remain unclear. Arabidopsis thaliana SMALL AUXIN UP RNA17 (SAUR17) is an apical-organ-specific regulator that promotes production of an apical hook and closed cotyledons. In darkness, ethylene and BRs stimulate SAUR17 expression by transcription factor complexes containing PHYTOCHROME-INTERACTING FACTORs (PIFs), ETHYLENE INSENSITIVE 3 (EIN3), and its homolog EIN3-LIKE 1 (EIL1), and BRASSINAZOLE RESISTANT1 (BZR1). BZR1 requires EIN3 and PIFs for enhanced DNA-binding and transcriptional activation of the SAUR17 promoter; while EIN3, PIF3, and PIF4 stability depends on BR signaling. BZR1 transcriptionally downregulates EIN3-BINDING F-BOX 1 and 2 (EBF1 and EBF2), which encode ubiquitin ligases mediating EIN3 and PIF3 protein degradation. By modulating the EBF-EIN3/PIF protein-stability circuit, BRs induce EIN3 and PIF3 accumulation, which underlies BR-responsive expression of SAUR17 and HOOKLESS1 and ultimately apical hook development. We suggest that in the etiolated development of apical structures, BRs primarily modulate plant sensitivity to darkness and ethylene.
Asunto(s)
Proteínas de Arabidopsis , Arabidopsis , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Oscuridad , Brasinoesteroides/farmacología , Brasinoesteroides/metabolismo , Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Etilenos/metabolismo , Plantones/genética , Plantones/metabolismo , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/metabolismoRESUMEN
The neuromodulator melatonin synchronizes circadian rhythms and related physiological functions through the actions of two G-protein-coupled receptors: MT1 and MT2. Circadian release of melatonin at night from the pineal gland activates melatonin receptors in the suprachiasmatic nucleus of the hypothalamus, synchronizing the physiology and behaviour of animals to the light-dark cycle1-4. The two receptors are established drug targets for aligning circadian phase to this cycle in disorders of sleep5,6 and depression1-4,7-9. Despite their importance, few in vivo active MT1-selective ligands have been reported2,8,10-12, hampering both the understanding of circadian biology and the development of targeted therapeutics. Here we docked more than 150 million virtual molecules to an MT1 crystal structure, prioritizing structural fit and chemical novelty. Of these compounds, 38 high-ranking molecules were synthesized and tested, revealing ligands with potencies ranging from 470 picomolar to 6 micromolar. Structure-based optimization led to two selective MT1 inverse agonists-which were topologically unrelated to previously explored chemotypes-that acted as inverse agonists in a mouse model of circadian re-entrainment. Notably, we found that these MT1-selective inverse agonists advanced the phase of the mouse circadian clock by 1.3-1.5 h when given at subjective dusk, an agonist-like effect that was eliminated in MT1- but not in MT2-knockout mice. This study illustrates the opportunities for modulating melatonin receptor biology through MT1-selective ligands and for the discovery of previously undescribed, in vivo active chemotypes from structure-based screens of diverse, ultralarge libraries.
Asunto(s)
Ritmo Circadiano/fisiología , Ligandos , Receptores de Melatonina/agonistas , Receptores de Melatonina/metabolismo , Animales , Ritmo Circadiano/efectos de los fármacos , Oscuridad , Evaluación Preclínica de Medicamentos , Agonismo Inverso de Drogas , Femenino , Humanos , Luz , Masculino , Ratones , Ratones Noqueados , Simulación del Acoplamiento Molecular , Receptor de Melatonina MT1/agonistas , Receptor de Melatonina MT1/deficiencia , Receptor de Melatonina MT1/genética , Receptor de Melatonina MT1/metabolismo , Receptor de Melatonina MT2/agonistas , Receptor de Melatonina MT2/deficiencia , Receptor de Melatonina MT2/genética , Receptor de Melatonina MT2/metabolismo , Receptores de Melatonina/deficiencia , Receptores de Melatonina/genética , Bibliotecas de Moléculas Pequeñas/farmacología , Especificidad por Sustrato/genéticaRESUMEN
Light plays an essential role in a variety of physiological processes, including vision, mood, and glucose homeostasis. However, the intricate relationship between light and an animal's feeding behavior has remained elusive. Here, we found that light exposure suppresses food intake, whereas darkness amplifies it in male mice. Interestingly, this phenomenon extends its reach to diurnal male Nile grass rats and healthy humans. We further show that lateral habenula (LHb) neurons in mice respond to light exposure, which in turn activates 5-HT neurons in the dorsal Raphe nucleus (DRN). Activation of the LHbâ5-HTDRN circuit in mice blunts darkness-induced hyperphagia, while inhibition of the circuit prevents light-induced anorexia. Together, we discovered a light-responsive neural circuit that relays the environmental light signals to regulate feeding behavior in mice.
Asunto(s)
Conducta Alimentaria , Habénula , Luz , Animales , Masculino , Ratones , Habénula/fisiología , Conducta Alimentaria/fisiología , Núcleo Dorsal del Rafe/fisiología , Humanos , Ratones Endogámicos C57BL , Ingestión de Alimentos/fisiología , Vías Nerviosas/fisiología , Ratas , Neuronas Serotoninérgicas/fisiología , Red Nerviosa/fisiología , OscuridadRESUMEN
Bathy phytochromes are a subclass of bacterial biliprotein photoreceptors that carry a biliverdin IXα chromophore. In contrast to prototypical phytochromes that adopt a red-light-absorbing Pr ground state, the far-red light-absorbing Pfr-form is the thermally stable ground state of bathy phytochromes. Although the photobiology of bacterial phytochromes has been extensively studied since their discovery in the late 1990s, our understanding of the signal transduction process to the connected transmitter domains, which are often histidine kinases, remains insufficient. Initiated by the analysis of the bathy phytochrome PaBphP from Pseudomonas aeruginosa, we performed a systematic analysis of five different bathy phytochromes with the aim to derive a general statement on the correlation of photostate and autokinase output. While all proteins adopt different Pr/Pfr-fractions in response to red, blue, and far-red light, only darkness leads to a pure or highly enriched Pfr-form, directly correlated with the lowest level of autokinase activity. Using this information, we developed a method to quantitatively correlate the autokinase activity of phytochrome samples with well-defined stationary Pr/Pfr-fractions. We demonstrate that the off-state of the phytochromes is the Pfr-form and that different Pr/Pfr-fractions enable the organisms to fine-tune their kinase output in response to a certain light environment. Furthermore, the output response is regulated by the rate of dark reversion, which differs significantly from 5 s to 50 min half-life. Overall, our study indicates that bathy phytochromes function as sensors of light and darkness, rather than red and far-red light, as originally postulated.
Asunto(s)
Proteínas Bacterianas , Oscuridad , Fitocromo , Proteínas Bacterianas/metabolismo , Proteínas Bacterianas/genética , Histidina Quinasa/metabolismo , Histidina Quinasa/genética , Luz , Fotorreceptores Microbianos/metabolismo , Fitocromo/metabolismo , Fitocromo/química , Pseudomonas aeruginosa/enzimología , Pseudomonas aeruginosa/metabolismo , Activación EnzimáticaRESUMEN
Rapid hypocotyl elongation allows buried seedlings to emerge, where light triggers de-etiolation and inhibits hypocotyl growth mainly by photoreceptors. Phosphorylation/dephosphorylation events regulate many aspects of plant development. Only recently we have begun to uncover the earliest phospho-signaling responders to light. Here, we reported a large-scale phosphoproteomic analysis and identified 20 proteins that changed their phosphorylation pattern following a 20 min light pulse compared to darkness. Microtubule-associated proteins were highly overrepresented in this group. Among them, we studied CIP7 (COP1-INTERACTING-PROTEIN 7), which presented microtubule (MT) localization in contrast to the previous description. An isoform of CIP7 phosphorylated at Serine915 was detected in etiolated seedlings but was undetectable after a light pulse in the presence of photoreceptors, while CIP7 transcript expression decays with long light exposure. The short hypocotyl phenotype and rearrangement of MTs in etiolated cip7 mutants are complemented by CIP7-YFP and the phospho-mimetic CIP7S915D-YFP, but not the phospho-null CIP7S915A-YFP suggesting that the phosphorylated S915CIP7 isoform promotes hypocotyl elongation through MT reorganization in darkness. Our evidence on Serine915 of CIP7 unveils phospho-regulation of MT-based processes during skotomorphogenic hypocotyl growth.
Asunto(s)
Proteínas de Arabidopsis , Arabidopsis , Oscuridad , Hipocótilo , Proteínas Asociadas a Microtúbulos , Hipocótilo/crecimiento & desarrollo , Hipocótilo/genética , Hipocótilo/metabolismo , Arabidopsis/crecimiento & desarrollo , Arabidopsis/metabolismo , Arabidopsis/genética , Arabidopsis/efectos de la radiación , Proteínas de Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Fosforilación , Proteínas Asociadas a Microtúbulos/metabolismo , Proteínas Asociadas a Microtúbulos/genética , Microtúbulos/metabolismo , Luz , Regulación de la Expresión Génica de las Plantas , Plantones/crecimiento & desarrollo , Plantones/genética , Plantones/metabolismo , Plantones/efectos de la radiaciónRESUMEN
Measurements of respiratory properties have often been made at a single time point either during daytime using dark-adapted leaves or during nighttime. The influence of the day-night cycle on respiratory metabolism has received less attention but is crucial to understand photosynthesis and photorespiration. Here, we examined how CO2- and O2-based rates of leaf dark respiration (Rdark) differed between midday (after 30-min dark adaptation) and midnight in 8 C3 and C4 grasses. We used these data to calculate the respiratory quotient (RQ; ratio of CO2 release to O2 uptake), and assessed relationships between Rdark and leaf metabolome. Rdark was higher at midday than midnight, especially in C4 species. The day-night difference in Rdark was more evident when expressed on a CO2 than O2 basis, with the RQ being higher at midday than midnight in all species, except in rice (Oryza sativa). Metabolomic analyses showed little correlation of Rdark or RQ with leaf carbohydrates (sucrose, glucose, fructose, or starch) but strong multivariate relationships with other metabolites. The results suggest that rates of Rdark and differences in RQ were determined by several concurrent CO2-producing and O2-consuming metabolic pathways, not only the tricarboxylic acid cycle (organic acids utilization) but also the pentose phosphate pathway, galactose metabolism, and secondary metabolism. As such, Rdark was time-, type- (C3/C4) and species-dependent, due to the use of different substrates.
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Dióxido de Carbono , Respiración de la Célula , Hojas de la Planta , Poaceae , Hojas de la Planta/metabolismo , Hojas de la Planta/fisiología , Poaceae/fisiología , Poaceae/metabolismo , Dióxido de Carbono/metabolismo , Fotosíntesis , Oscuridad , Oxígeno/metabolismo , MetabolomaRESUMEN
Dark-induced senescence provokes profound metabolic shifts to recycle nutrients and to guarantee plant survival. To date, research on these processes has largely focused on characterizing mutants deficient in individual pathways. Here, we adopted a time-resolved genome-wide association-based approach to characterize dark-induced senescence by evaluating the photochemical efficiency and content of primary and lipid metabolites at the beginning, or after 3 or 6 days in darkness. We discovered six patterns of metabolic shifts and identified 215 associations with 81 candidate genes being involved in this process. Among these associations, we validated the roles of four genes associated with glycine, galactinol, threonine, and ornithine levels. We also demonstrated the function of threonine and galactinol catabolism during dark-induced senescence. Intriguingly, we determined that the association between tyrosine contents and TYROSINE AMINOTRANSFERASE 1 influences enzyme activity of the encoded protein and transcriptional activity of the gene under normal and dark conditions, respectively. Moreover, the single-nucleotide polymorphisms affecting the expression of THREONINE ALDOLASE 1 and the amino acid transporter gene AVT1B, respectively, only underlie the variation in threonine and glycine levels in the dark. Taken together, these results allow us to present a very detailed model of the metabolic aspects of dark-induced senescence, as well as the process itself.
Asunto(s)
Arabidopsis/fisiología , Oscuridad , Genes de Plantas , Senescencia de la Planta/genética , Estudio de Asociación del Genoma CompletoRESUMEN
CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1), a well-characterized E3 ubiquitin ligase, is a central repressor of seedling photomorphogenic development in darkness. However, whether COP1 is involved in modulating abscisic acid (ABA) signaling in darkness remains largely obscure. Here, we report that COP1 is a positive regulator of ABA signaling during Arabidopsis seedling growth in the dark. COP1 mediates ABA-induced accumulation of ABI5, a transcription factor playing a key role in ABA signaling, through transcriptional and post-translational regulatory mechanisms. We further show that COP1 physically interacts with ABA-hypersensitive DCAF1 (ABD1), a substrate receptor of the CUL4-DDB1 E3 ligase targeting ABI5 for degradation. Accordingly, COP1 directly ubiquitinates ABD1 in vitro, and negatively regulates ABD1 protein abundance in vivo in the dark but not in the light. Therefore, COP1 promotes ABI5 protein stability post-translationally in darkness by destabilizing ABD1 in response to ABA. Interestingly, we reveal that ABA induces the nuclear accumulation of COP1 in darkness, thus enhancing its activity in propagating the ABA signal. Together, our study uncovers that COP1 modulates ABA signaling during seedling growth in darkness by mediating ABA-induced ABI5 accumulation, demonstrating that plants adjust their ABA signaling mechanisms according to their light environment.
Asunto(s)
Proteínas de Arabidopsis , Arabidopsis , Ácido Abscísico/metabolismo , Ácido Abscísico/farmacología , Arabidopsis/metabolismo , Proteínas de Arabidopsis/metabolismo , Factores de Transcripción con Cremalleras de Leucina de Carácter Básico/genética , Factores de Transcripción con Cremalleras de Leucina de Carácter Básico/metabolismo , Oscuridad , Regulación de la Expresión Génica de las Plantas , Plantones/metabolismo , Ubiquitina-Proteína Ligasas/metabolismoRESUMEN
Leaf senescence is a critical process in plants and has a direct impact on many important agronomic traits. Despite decades of research on senescence-altered mutants via forward genetics and functional assessment of senescence-associated genes (SAGs) via reverse genetics, the senescence signal and the molecular mechanism that perceives and transduces the signal remain elusive. Here, using dark-induced senescence (DIS) of Arabidopsis leaf as the experimental system, we show that exogenous copper induces the senescence syndrome and transcriptomic changes in light-grown plants parallel to those in DIS. By profiling the transcriptomes and tracking the subcellular copper distribution, we found that reciprocal regulation of plastocyanin, the thylakoid lumen mobile electron carrier in the Z scheme of photosynthetic electron transport, and SAG14 and plantacyanin (PCY), a pair of interacting small blue copper proteins located on the endomembrane, is a common thread in different leaf senescence scenarios, including DIS. Genetic and molecular experiments confirmed that the PCY-SAG14 module is necessary and sufficient for promoting DIS. We also found that the PCY-SAG14 module is repressed by a conserved microRNA, miR408, which in turn is repressed by phytochrome interacting factor 3/4/5 (PIF3/4/5), the key trio of transcription factors promoting DIS. Together, these findings indicate that intracellular copper redistribution mediated by PCY-SAG14 has a regulatory role in DIS. Further deciphering the copper homeostasis mechanism and its interaction with other senescence-regulating pathways should provide insights into our understanding of the fundamental question of how plants age.
Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , MicroARNs/metabolismo , Hojas de la Planta/metabolismo , Senescencia de la Planta/fisiología , Arabidopsis/genética , Cobre , Oscuridad , Regulación de la Expresión Génica de las Plantas , Luz , Fitocromo/metabolismo , Senescencia de la Planta/genética , Plantas Modificadas Genéticamente , Factores de Transcripción/metabolismo , TranscriptomaRESUMEN
The aging eye experiences physiological changes that include decreased visual function and increased risk of retinal degeneration. Although there are transcriptomic signatures in the aging retina that correlate with these physiological changes, the gene regulatory mechanisms that contribute to cellular homeostasis during aging remain to be determined. Here, we integrated ATAC-seq and RNA-seq data to identify 57 transcription factors that showed differential activity in aging Drosophila photoreceptors. These 57 age-regulated transcription factors include two circadian regulators, Clock and Cycle, that showed sustained increased activity during aging. When we disrupted the Clock:Cycle complex by expressing a dominant negative version of Clock (ClkDN) in adult photoreceptors, we observed changes in expression of 15-20% of genes including key components of the phototransduction machinery and many eye-specific transcription factors. Using ATAC-seq, we showed that expression of ClkDN in photoreceptors leads to changes in activity of 37 transcription factors and causes a progressive decrease in global levels of chromatin accessibility in photoreceptors. Supporting a key role for Clock-dependent transcription in the eye, expression of ClkDN in photoreceptors also induced light-dependent retinal degeneration and increased oxidative stress, independent of light exposure. Together, our data suggests that the circadian regulators Clock and Cycle act as neuroprotective factors in the aging eye by directing gene regulatory networks that maintain expression of the phototransduction machinery and counteract oxidative stress.