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1.
Int J Mol Sci ; 23(8)2022 Apr 08.
Artigo em Inglês | MEDLINE | ID: mdl-35456963

RESUMO

Lycopene content is one of the important factors for determining watermelon fruit quality. In this study, a small-type watermelon was grown in a greenhouse with supplementary red lighting for 10 h per day. The results showed that the content of lycopene in the flesh was increased 6.3-fold after 25 days of supplementary red lighting. qRT-PCR analysis showed that PHYTOENE SYNTHASE 1(ClPSY1) is the major gene that responds to red light within the lycopene synthesis pathway. Moreover, we identified two key transcription factors that were involved in light signal transduction PHYTOCHROME INTERACTING FACTORS 3 (ClPIF3) and LONG HYPOCOTYL 5 (ClHY5) in watermelon flesh. The interaction experiments showed that ClHY5, a potent ClPIF3 antagonist, regulated ClPSY1 expression by directly targeting a common promoter cis-element (G-box). Collectively, our findings identified that ClHY5 and ClPIF3 formed an activation-suppression transcriptional module that is responsive to red light and, through this model, regulated watermelon lycopene accumulation in greenhouse winter cultivation.


Assuntos
Citrullus , Citrullus/genética , Citrullus/metabolismo , Frutas/genética , Frutas/metabolismo , Transdução de Sinal Luminoso , Iluminação , Licopeno/metabolismo
2.
Commun Biol ; 5(1): 190, 2022 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-35233102

RESUMO

Numerous missense mutations in cyclic nucleotide-gated (CNG) channels cause achromatopsia and retinitis pigmentosa, but the underlying pathogenic mechanisms are often unclear. We investigated the structural basis and molecular/cellular effects of R410W, an achromatopsia-associated, presumed loss-of-function mutation in human CNGA3. Cryo-EM structures of the Caenorhabditis elegans TAX-4 CNG channel carrying the analogous mutation, R421W, show that most apo channels are open. R421, located in the gating ring, interacts with the S4 segment in the closed state. R421W disrupts this interaction, destabilizes the closed state, and stabilizes the open state. CNGA3_R410W/CNGB3 and TAX4_R421W channels are spontaneously active without cGMP and induce cell death, suggesting cone degeneration triggered by spontaneous CNG channel activity as a possible cause of achromatopsia. Our study sheds new light on CNG channel allosteric gating, provides an impetus for a reevaluation of reported loss-of-function CNG channel missense disease mutations, and has implications for mutation-specific treatment of retinopathy.


Assuntos
Defeitos da Visão Cromática , Canais de Cátion Regulados por Nucleotídeos Cíclicos , Defeitos da Visão Cromática/genética , Defeitos da Visão Cromática/metabolismo , Defeitos da Visão Cromática/patologia , Canais de Cátion Regulados por Nucleotídeos Cíclicos/química , Canais de Cátion Regulados por Nucleotídeos Cíclicos/genética , Canais de Cátion Regulados por Nucleotídeos Cíclicos/metabolismo , Humanos , Transdução de Sinal Luminoso , Mutação de Sentido Incorreto , Células Fotorreceptoras Retinianas Cones
3.
Genes (Basel) ; 13(2)2022 01 29.
Artigo em Inglês | MEDLINE | ID: mdl-35205309

RESUMO

Advanced age is one of the leading risk factors for vision loss and eye disease. Photoreceptors are the primary sensory neurons of the eye. The extended photoreceptor cell lifespan, in addition to its high metabolic needs due to phototransduction, makes it critical for these neurons to continually respond to the stresses associated with aging by mounting an appropriate gene expression response. Here, we sought to untangle the more general neuronal age-dependent transcriptional signature of photoreceptors with that induced by light stress. To do this, we aged flies or exposed them to various durations of blue light, followed by photoreceptor nuclei-specific transcriptome profiling. Using this approach, we identified genes that are both common and uniquely regulated by aging and light induced stress. Whereas both age and blue light induce expression of DNA repair genes and a neuronal-specific signature of death, both conditions result in downregulation of phototransduction. Interestingly, blue light uniquely induced genes that directly counteract the overactivation of the phototransduction signaling cascade. Lastly, unique gene expression changes in aging photoreceptors included the downregulation of genes involved in membrane potential homeostasis and mitochondrial function, as well as the upregulation of immune response genes. We propose that light stress contributes to the aging transcriptome of photoreceptors, but that there are also other environmental or intrinsic factors involved in age-associated photoreceptor gene expression signatures.


Assuntos
Transdução de Sinal Luminoso , Células Fotorreceptoras , Perfilação da Expressão Gênica , Transdução de Sinal Luminoso/genética , Células Fotorreceptoras/metabolismo , Transcriptoma
4.
Proc Natl Acad Sci U S A ; 119(9)2022 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-35197287

RESUMO

Rhodopsin and cone opsins are essential for light detection in vertebrate rods and cones, respectively. It is well established that rhodopsin is required for rod phototransduction, outer segment disk morphogenesis, and rod viability. However, the roles of cone opsins are less well understood. In this study, we adopted a loss-of-function approach to investigate the physiological roles of cone opsins in mice. We showed that cones lacking cone opsins do not form normal outer segments due to the lack of disk morphogenesis. Surprisingly, cone opsin-deficient cones survive for at least 12 mo, which is in stark contrast to the rapid rod degeneration observed in rhodopsin-deficient mice, suggesting that cone opsins are dispensable for cone viability. Although the mutant cones do not respond to light directly, they maintain a normal dark current and continue to mediate visual signaling by relaying the rod signal through rod-cone gap junctions. Our work reveals a striking difference between the role of rhodopsin and cone opsins in photoreceptor viability.


Assuntos
Células Fotorreceptoras Retinianas Cones/metabolismo , Pigmentos da Retina/metabolismo , Transdução de Sinais , Animais , Opsinas dos Cones/genética , Eletrorretinografia , Transdução de Sinal Luminoso , Mutação com Perda de Função , Camundongos
5.
Int J Mol Sci ; 23(3)2022 Jan 18.
Artigo em Inglês | MEDLINE | ID: mdl-35162940

RESUMO

Vitamin A is an essential fat-soluble vitamin that occurs in various chemical forms. It is essential for several physiological processes. Either hyper- or hypovitaminosis can be harmful. One of the most important vitamin A functions is its involvement in visual phototransduction, where it serves as the crucial part of photopigment, the first molecule in the process of transforming photons of light into electrical signals. In this process, large quantities of vitamin A in the form of 11-cis-retinal are being isomerized to all-trans-retinal and then quickly recycled back to 11-cis-retinal. Complex machinery of transporters and enzymes is involved in this process (i.e., the visual cycle). Any fault in the machinery may not only reduce the efficiency of visual detection but also cause the accumulation of toxic chemicals in the retina. This review provides a comprehensive overview of diseases that are directly or indirectly connected with vitamin A pathways in the retina. It includes the pathophysiological background and clinical presentation of each disease and summarizes the already existing therapeutic and prospective interventions.


Assuntos
Doenças Retinianas/metabolismo , Vitamina A/metabolismo , Regulação da Expressão Gênica , Humanos , Transdução de Sinal Luminoso , Transdução de Sinais
6.
Int J Mol Sci ; 23(2)2022 Jan 08.
Artigo em Inglês | MEDLINE | ID: mdl-35054872

RESUMO

Light is essential for photosynthesis but light levels that exceed an organism's assimilation capacity can cause serious damage or even cell death. Plants and microalgae have developed photoprotective mechanisms collectively referred to as non-photochemical quenching to minimize such potential damage. One such mechanism is energy-dependent quenching (qE), which dissipates excess light energy as heat. Over the last 30 years, much has been learned about the molecular mechanism of qE in green algae and plants. However, the steps between light perception and qE represented a gap in our knowledge until the recent identification of light-signaling pathways that function in these processes in the green alga Chlamydomonas reinhardtii. In this review, we summarize the high light and UV-mediated signaling pathways for qE in Chlamydomonas. We discuss key questions remaining about the pathway from light perception to photoprotective gene expression in Chlamydomonas. We detail possible differences between green algae and plants in light-signaling mechanisms for qE and emphasize the importance of research on light-signaling mechanisms for qE in plants.


Assuntos
Chlamydomonas reinhardtii/genética , Chlamydomonas reinhardtii/efeitos da radiação , Regulação da Expressão Gênica de Plantas , Transdução de Sinal Luminoso , Processos Fotoquímicos , Luz , Transdução de Sinal Luminoso/efeitos da radiação , Modelos Biológicos
7.
Mol Med Rep ; 25(2)2022 02.
Artigo em Inglês | MEDLINE | ID: mdl-35014690

RESUMO

Optogenetics combined with protein engineering based on natural light­sensitive dimerizing proteins has evolved as a powerful strategy to study cellular functions. The present study focused on tropomyosin kinase receptors (Trks) that have been engineered to be light­sensitive. Trk belongs to the superfamily of receptor tyrosine kinases (RTKs), which are single­pass transmembrane receptors that are activated by natural ligands and serve crucial roles in cellular growth, differentiation, metabolism and motility. However, functional variations exist among receptors fused with light­sensitive proteins. The present study proposed a signal transduction model for light­induced receptor activation. This model is based on analysis of previous light­induced Trk receptors reported to date and comparisons to the activation mechanism of natural receptors. In this model, quantitative differences on the dimerization induced from either top­to­bottom or bottom­to­up may lead to the varying amplitude of intracellular signals. We hypothesize that the top­to­bottom propagation is more favourable for activation and yields better results compared with the bottom­to­top direction. The careful delineation of the dimerization mechanisms fine­tuning activation will guide future design for an optimum cellular output with the precision of light.


Assuntos
Fatores de Crescimento Neural/metabolismo , Receptores Proteína Tirosina Quinases/metabolismo , Dimerização , Humanos , Luz , Transdução de Sinal Luminoso , Modelos Biológicos , Receptor de Insulina/química , Receptor de Insulina/metabolismo , Receptor trkA/química , Receptor trkA/metabolismo
8.
PLoS Genet ; 18(1): e1010021, 2022 01.
Artigo em Inglês | MEDLINE | ID: mdl-35100266

RESUMO

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.


Assuntos
Proteínas CLOCK/fisiologia , Proteínas de Drosophila/fisiologia , Drosophila/genética , Células Fotorreceptoras de Invertebrados/metabolismo , Degeneração Retiniana/prevenção & controle , Transcrição Genética/fisiologia , Envelhecimento/genética , Animais , Relógios Circadianos , Escuridão , Transdução de Sinal Luminoso/genética , Degeneração Retiniana/metabolismo , Transcriptoma
9.
Mol Ecol Resour ; 22(2): 587-601, 2022 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-34652059

RESUMO

The diversity of avian visual phenotypes provides a framework for studying mechanisms of trait diversification generally, and the evolution of vertebrate vision, specifically. Previous research has focused on opsins, but to fully understand visual adaptation, we must study the complete phototransduction cascade (PTC). Here, we developed a probe set that captures exonic regions of 46 genes representing the PTC and other light responses. For a subset of species, we directly compared gene capture between our probe set and low-coverage whole genome sequencing (WGS), and we discuss considerations for choosing between these methods. Finally, we developed a unique strategy to avoid chimeric assembly by using "decoy" reference sequences. We successfully captured an average of 64% of our targeted exome in 46 species across 14 orders using the probe set and had similar recovery using the WGS data. Compared to WGS or transcriptomes, our probe set: (1) reduces sequencing requirements by efficiently capturing vision genes, (2) employs a simpler bioinformatic pipeline by limiting required assembly and negating annotation, and (3) eliminates the need for fresh tissues, enabling researchers to leverage existing museum collections. We then utilized our vision exome data to identify positively selected genes in two evolutionary scenarios-evolution of night vision in nocturnal birds and evolution of high-speed vision specific to manakins (Pipridae). We found parallel positive selection of SLC24A1 in both scenarios, implicating the alteration of rod response kinetics, which could improve color discrimination in dim light conditions and/or facilitate higher temporal resolution.


Assuntos
Aves , Exoma , Animais , Aves/genética , Transdução de Sinal Luminoso/genética , Opsinas/genética , Sequenciamento Completo do Exoma
10.
New Phytol ; 233(5): 2127-2143, 2022 03.
Artigo em Inglês | MEDLINE | ID: mdl-34936108

RESUMO

Plants have evolved sophisticated regulatory networks to cope with dynamically changing light and temperature environments during day-night and seasonal cycles. However, the integration mechanisms of light and low temperature remain largely unclear. Here, we show that low red : far-red ratio (LR : FR) induces FAR-RED ELONGATED HYPOCOTYL3 (SlFHY3) transcription under cold stress in tomato (Solanum lycopersicum). Reverse genetic approaches revealed that knocking out SlFHY3 decreases myo-inositol accumulation and increases cold susceptibility, whereas overexpressing SlFHY3 induces myo-inositol accumulation and enhances cold tolerance in tomato plants. SlFHY3 physically interacts with ELONGATED HYPOCOTYL5 (SlHY5) to promote the transcriptional activity of SlHY5 on MYO-INOSITOL-1-PHOSPHATE SYNTHASE 3 (SlMIPS3) and induce myo-inositol accumulation in tomato plants under cold stress. Disruption of SlHY5 and SlMIPS3 largely suppresses the cold tolerance of SlFHY3-overexpressing plants and myo-inositol accumulation in tomato. Furthermore, silencing of SlMIPS3 drastically reduces myo-inositol accumulation and compromises LR : FR-induced cold tolerance in tomato. Together, our results reveal a crucial role of SlFHY3 in LR : FR-induced cold tolerance in tomato and unravel a novel regulatory mechanism whereby plants integrate dynamic environmental light signals and internal cues (inositol biosynthesis) to induce and control cold tolerance in tomato plants.


Assuntos
Lycopersicon esculentum , Temperatura Baixa , Regulação da Expressão Gênica de Plantas , Inositol , Transdução de Sinal Luminoso , Lycopersicon esculentum/genética
11.
Sci Rep ; 11(1): 23424, 2021 12 06.
Artigo em Inglês | MEDLINE | ID: mdl-34873237

RESUMO

Intrinsically-photosensitive retinal ganglion cells (ipRGCs) are non-rod/non-cone retinal photoreceptors expressing the visual pigment, melanopsin, to detect ambient irradiance for various non-image-forming visual functions. The M1-subtype, amongst the best studied, mediates primarily circadian photoentrainment and pupillary light reflex. Their intrinsic light responses are more prolonged than those of rods and cones even at the single-photon level, in accordance with the typically slower time course of non-image-forming vision. The short (OPN4S) and long (OPN4L) alternatively-spliced forms of melanopsin proteins are both present in M1-ipRGCs, but their functional difference is unclear. We have examined this point by genetically removing the Opn4 gene (Opn4-/-) in mouse and re-expressing either OPN4S or OPN4L singly in Opn4-/- mice by using adeno-associated virus, but found no obvious difference in their intrinsic dim-flash responses. Previous studies have indicated that two dominant slow steps in M1-ipRGC phototransduction dictate these cells' intrinsic dim-flash-response kinetics, with time constants (τ1 and τ2) at room temperature of ~ 2 s and ~ 20 s, respectively. Here we found that melanopsin inactivation by phosphorylation or by ß-arrestins may not be one of these two steps, because their genetic disruptions did not prolong the two time constants or affect the response waveform. Disruption of GAP (GTPase-Activating-Protein) activity on the effector enzyme, PLCß4, in M1-ipRGC phototransduction to slow down G-protein deactivation also did not prolong the response decay, but caused its rising phase to become slightly sigmoidal by giving rise to a third time constant, τ3, of ~ 2 s (room temperature). This last observation suggests that GAP-mediated G-protein deactivation does partake in the flash-response termination, although normally with a time constant too short to be visible in the response waveform.


Assuntos
Células Fotorreceptoras Retinianas Cones/metabolismo , Células Ganglionares da Retina/metabolismo , Animais , Ritmo Circadiano/fisiologia , Dependovirus , Injeções Intravítreas , Cinética , Luz , Transdução de Sinal Luminoso , Camundongos , Camundongos Transgênicos , Mutação , Neurociências , Fosforilação , Opsinas de Bastonetes/química , Transdução de Sinais , Visão Ocular , beta-Arrestinas/química
12.
Int J Mol Sci ; 22(24)2021 Dec 13.
Artigo em Inglês | MEDLINE | ID: mdl-34948198

RESUMO

Green rods (GRs) represent a unique type of photoreceptor to be found in the retinas of anuran amphibians. These cells harbor a cone-specific blue-sensitive visual pigment but exhibit morphology of the outer segment typical for classic red rods (RRs), which makes them a perspective model object for studying cone-rod transmutation. In the present study, we performed detailed electrophysiological examination of the light sensitivity, response kinetics and parameters of discrete and continuous dark noise in GRs of the two anuran species: cane toad and marsh frog. Our results confirm that anuran GRs are highly specialized nocturnal vision receptors. Moreover, their rate of phototransduction quenching appeared to be about two-times slower than in RRs, which makes them even more efficient single photon detectors. The operating intensity ranges for two rod types widely overlap supposedly allowing amphibians to discriminate colors in the scotopic region. Unexpectedly for typical cone pigments but in line with some previous reports, the spontaneous isomerization rate of the GR visual pigment was found to be the same as for rhodopsin of RRs. Thus, our results expand the knowledge on anuran GRs and show that these are even more specialized single photon catchers than RRs, which allows us to assign them a status of "super-rods".


Assuntos
Transdução de Sinal Luminoso/fisiologia , Células Fotorreceptoras Retinianas Cones/metabolismo , Células Fotorreceptoras Retinianas Bastonetes/metabolismo , Animais , Anuros/anatomia & histologia , Isomerismo , Cinética , Luz , Visão Noturna/fisiologia , Células Fotorreceptoras de Vertebrados/metabolismo , Células Fotorreceptoras de Vertebrados/fisiologia , Retina/anatomia & histologia , Retina/metabolismo , Células Fotorreceptoras Retinianas Cones/fisiologia , Células Fotorreceptoras Retinianas Bastonetes/fisiologia , Rodopsina , Opsinas de Bastonetes , Visão Ocular/fisiologia
13.
Int J Mol Sci ; 22(21)2021 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-34768741

RESUMO

Bioluminescence, the emission of light catalysed by luciferases, has evolved in many taxa from bacteria to vertebrates and is predominant in the marine environment. It is now well established that in animals possessing a nervous system capable of integrating light stimuli, bioluminescence triggers various behavioural responses and plays a role in intra- or interspecific visual communication. The function of light emission in unicellular organisms is less clear and it is currently thought that it has evolved in an ecological framework, to be perceived by visual animals. For example, while it is thought that bioluminescence allows bacteria to be ingested by zooplankton or fish, providing them with favourable conditions for growth and dispersal, the luminous flashes emitted by dinoflagellates may have evolved as an anti-predation system against copepods. In this short review, we re-examine this paradigm in light of recent findings in microorganism photoreception, signal integration and complex behaviours. Numerous studies show that on the one hand, bacteria and protists, whether autotrophs or heterotrophs, possess a variety of photoreceptors capable of perceiving and integrating light stimuli of different wavelengths. Single-cell light-perception produces responses ranging from phototaxis to more complex behaviours. On the other hand, there is growing evidence that unicellular prokaryotes and eukaryotes can perform complex tasks ranging from habituation and decision-making to associative learning, despite lacking a nervous system. Here, we focus our analysis on two taxa, bacteria and dinoflagellates, whose bioluminescence is well studied. We propose the hypothesis that similar to visual animals, the interplay between light-emission and reception could play multiple roles in intra- and interspecific communication and participate in complex behaviour in the unicellular world.


Assuntos
Transdução de Sinal Luminoso/fisiologia , Proteínas Luminescentes/metabolismo , Células Fotorreceptoras/fisiologia , Animais , Bactérias/metabolismo , Comunicação , Dinoflagelados/metabolismo , Luz , Luciferases/metabolismo , Medições Luminescentes , Células Fotorreceptoras/metabolismo , Plâncton/metabolismo , Comportamento Predatório
14.
J Exp Biol ; 224(23)2021 12 01.
Artigo em Inglês | MEDLINE | ID: mdl-34842918

RESUMO

Melanopsin is a visual pigment that is expressed in a small subset of intrinsically photosensitive retinal ganglion cells (ipRGCs). It is involved in regulating non-image forming visual behaviors, such as circadian photoentrainment and the pupillary light reflex, while also playing a role in many aspects of image-forming vision, such as contrast sensitivity. Melanopsin was initially discovered in the melanophores of the skin of the frog Xenopus, and subsequently found in a subset of ganglion cells in rat, mouse and primate retinas. ipRGCs were initially thought to be a single retinal ganglion cell population, and melanopsin was thought to activate a single, invertebrate-like Gq/transient receptor potential canonical (TRPC)-based phototransduction cascade within these cells. However, in the 20 years since the discovery of melanopsin, our knowledge of this visual pigment and ipRGCs has expanded dramatically. Six ipRGC subtypes have now been identified in the mouse, each with unique morphological, physiological and functional properties. Multiple subtypes have also been identified in other species, suggesting that this cell type diversity is a general feature of the ipRGC system. This diversity has led to a renewed interest in melanopsin phototransduction that may not follow the canonical Gq/TRPC cascade in the mouse or in the plethora of other organisms that express the melanopsin photopigment. In this Review, we discuss recent findings and discoveries that have challenged the prevailing view of melanopsin phototransduction as a single pathway that influences solely non-image forming functions.


Assuntos
Transdução de Sinal Luminoso , Opsinas de Bastonetes , Animais , Camundongos , Ratos , Retina , Células Ganglionares da Retina
15.
PLoS One ; 16(10): e0258721, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34710119

RESUMO

In daylight, cone photoreceptors in the retina are responsible for the bulk of visual perception, yet compared to rods, far less is known quantitatively about their biochemistry. This is partly because it is hard to isolate and purify cone proteins. The issue is also complicated by the synergistic interaction of these parameters in producing systems biology outputs, such as photoresponse. Using a 3-D resolved, finite element model of cone outer segments, here we conducted a study of parameter significance using global sensitivity analysis, by Sobol indices, which was contextualized within the uncertainty surrounding these parameters in the available literature. The analysis showed that a subset of the parameters influencing the circulating dark current, such as the turnover rate of cGMP in the dark, may be most influential for variance with experimental flash response, while the shut-off rates of photoexcited rhodopsin and phosphodiesterase also exerted sizable effect. The activation rate of transducin by rhodopsin and the light-induced hydrolysis rate of cGMP exerted measurable effects as well but were estimated as relatively less significant. The results of this study depend on experimental ranges currently described in the literature and should be revised as these become better established. To that end, these findings may be used to prioritize parameters for measurement in future investigations.


Assuntos
GMP Cíclico/metabolismo , Transdução de Sinal Luminoso , Luz , Células Fotorreceptoras Retinianas Cones/fisiologia , Transducina/fisiologia , Visão Ocular/fisiologia , Animais , Camundongos , Camundongos Knockout
16.
Int J Mol Sci ; 22(19)2021 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-34639112

RESUMO

Interaction between light signaling and stress response has been recently reported in plants. Here, we investigated the role of CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1), a key regulator of light signaling, in endoplasmic reticulum (ER) stress response in Arabidopsis. The cop1-4 mutant Arabidopsis plants were highly sensitive to ER stress induced by treatment with tunicarmycin (Tm). Interestingly, the abundance of nuclear-localized COP1 increased under ER stress conditions. Complementation of cop1-4 mutant plants with the wild-type or variant types of COP1 revealed that the nuclear localization and dimerization of COP1 are essential for its function in plant ER stress response. Moreover, the protein amount of ELONGATED HYPOCOTYL 5 (HY5), which inhibits bZIP28 to activate the unfolded protein response (UPR), decreased under ER stress conditions in a COP1-dependent manner. Accordingly, the binding of bZIP28 to the BIP3 promoter was reduced in cop1-4 plants and increased in hy5 plants compared with the wild type. Furthermore, introduction of the hy5 mutant locus into the cop1-4 mutant background rescued its ER stress-sensitive phenotype. Altogether, our results suggest that COP1, a negative regulator of light signaling, positively controls ER stress response by partially degrading HY5 in the nucleus.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/fisiologia , Estresse do Retículo Endoplasmático , Regulação da Expressão Gênica de Plantas , Transdução de Sinal Luminoso , Ubiquitina-Proteína Ligases/metabolismo , Resposta a Proteínas não Dobradas , Proteínas de Arabidopsis/genética , Ubiquitina-Proteína Ligases/genética
17.
Int J Mol Sci ; 22(19)2021 Oct 06.
Artigo em Inglês | MEDLINE | ID: mdl-34639157

RESUMO

Guanylate cyclase-activating protein 1 (GCAP1), encoded by the GUCA1A gene, is a neuronal calcium sensor protein involved in shaping the photoresponse kinetics in cones and rods. GCAP1 accelerates or slows the cGMP synthesis operated by retinal guanylate cyclase (GC) based on the light-dependent levels of intracellular Ca2+, thereby ensuring a timely regulation of the phototransduction cascade. We found a novel variant of GUCA1A in a patient affected by autosomal dominant cone dystrophy (adCOD), leading to the Asn104His (N104H) amino acid substitution at the protein level. While biochemical analysis of the recombinant protein showed impaired Ca2+ sensitivity of the variant, structural properties investigated by circular dichroism and limited proteolysis excluded major structural rearrangements induced by the mutation. Analytical gel filtration profiles and dynamic light scattering were compatible with a dimeric protein both in the presence of Mg2+ alone and Mg2+ and Ca2+. Enzymatic assays showed that N104H-GCAP1 strongly interacts with the GC, with an affinity that doubles that of the WT. The doubled IC50 value of the novel variant (520 nM for N104H vs. 260 nM for the WT) is compatible with a constitutive activity of GC at physiological levels of Ca2+. The structural region at the interface with the GC may acquire enhanced flexibility under high Ca2+ conditions, as suggested by 2 µs molecular dynamics simulations. The altered interaction with GC would cause hyper-activity of the enzyme at both low and high Ca2+ levels, which would ultimately lead to toxic accumulation of cGMP and Ca2+ in the photoreceptor outer segment, thus triggering cell death.


Assuntos
Distrofia de Cones/patologia , GMP Cíclico/metabolismo , Proteínas Ativadoras de Guanilato Ciclase/genética , Guanilato Ciclase/metabolismo , Mutação , Retina/enzimologia , Células Fotorreceptoras Retinianas Bastonetes/metabolismo , Adolescente , Cálcio/metabolismo , Criança , Distrofia de Cones/genética , Distrofia de Cones/metabolismo , Feminino , Humanos , Transdução de Sinal Luminoso , Masculino , Pessoa de Meia-Idade , Linhagem , Transdução de Sinais
18.
Elife ; 102021 09 22.
Artigo em Inglês | MEDLINE | ID: mdl-34550876

RESUMO

Eukaryotes generally display a circadian rhythm as an adaption to the reoccurring day/night cycle. This is particularly true for visual physiology that is directly affected by changing light conditions. Here we investigate the influence of the circadian rhythm on the expression and function of visual transduction cascade regulators in diurnal zebrafish and nocturnal mice. We focused on regulators of shut-off kinetics such as Recoverins, Arrestins, Opsin kinases, and Regulator of G-protein signaling that have direct effects on temporal vision. Transcript as well as protein levels of most analyzed genes show a robust circadian rhythm-dependent regulation, which correlates with changes in photoresponse kinetics. Electroretinography demonstrates that photoresponse recovery in zebrafish is delayed in the evening and accelerated in the morning. Functional rhythmicity persists in continuous darkness, and it is reversed by an inverted light cycle and disrupted by constant light. This is in line with our finding that orthologous gene transcripts from diurnal zebrafish and nocturnal mice are often expressed in an anti-phasic daily rhythm.


Assuntos
Ritmo Circadiano/efeitos da radiação , Células Fotorreceptoras de Vertebrados/efeitos da radiação , Células Fotorreceptoras Retinianas Cones/efeitos da radiação , Animais , Arrestinas/genética , Arrestinas/metabolismo , Escuridão , Eletrorretinografia , Feminino , Receptor Quinase 1 Acoplada a Proteína G/genética , Receptor Quinase 1 Acoplada a Proteína G/metabolismo , Luz , Transdução de Sinal Luminoso , Masculino , Camundongos , Modelos Animais , Células Fotorreceptoras de Vertebrados/metabolismo , Proteínas RGS/genética , Proteínas RGS/metabolismo , Células Fotorreceptoras Retinianas Cones/metabolismo , Visão Ocular/efeitos da radiação , Peixe-Zebra/genética , Peixe-Zebra/metabolismo
19.
Plant Cell ; 33(11): 3555-3573, 2021 11 04.
Artigo em Inglês | MEDLINE | ID: mdl-34427646

RESUMO

Light and temperature are two key environmental factors that coordinately regulate plant growth and development. Although the mechanisms that integrate signaling mediated by cold and red light have been unraveled, the roles of the blue light photoreceptors cryptochromes in plant responses to cold remain unclear. In this study, we demonstrate that the CRYPTOCHROME2 (CRY2)-COP1-HY5-BBX7/8 module regulates blue light-dependent cold acclimation in Arabidopsis thaliana. We show that phosphorylated forms of CRY2 induced by blue light are stabilized by cold stress and that cold-stabilized CRY2 competes with the transcription factor HY5 to attenuate the HY5-COP1 interaction, thereby allowing HY5 to accumulate at cold temperatures. Furthermore, our data demonstrate that B-BOX DOMAIN PROTEIN7 (BBX7) and BBX8 function as direct HY5 targets that positively regulate freezing tolerance by modulating the expression of a set of cold-responsive genes, which mainly occurs independently of the C-repeat-binding factor pathway. Our study uncovers a mechanistic framework by which CRY2-mediated blue-light signaling enhances freezing tolerance, shedding light on the molecular mechanisms underlying the crosstalk between cold and light signaling pathways in plants.


Assuntos
Aclimatação/genética , Arabidopsis/fisiologia , Temperatura Baixa , Transdução de Sinal Luminoso/genética , Luz , Arabidopsis/genética
20.
Sci Rep ; 11(1): 17340, 2021 08 30.
Artigo em Inglês | MEDLINE | ID: mdl-34462505

RESUMO

Vertebrate photoreceptors are categorized into two broad classes, rods and cones, responsible for dim- and bright-light vision, respectively. While many molecular features that distinguish rods and cones are known, gene expression differences among cone subtypes remain poorly understood. Teleost fishes are renowned for the diversity of their photoreceptor systems. Here, we used single-cell RNA-seq to profile adult photoreceptors in zebrafish, a teleost. We found that in addition to the four canonical zebrafish cone types, there exist subpopulations of green and red cones (previously shown to be located in the ventral retina) that express red-shifted opsin paralogs (opn1mw4 or opn1lw1) as well as a unique combination of cone phototransduction genes. Furthermore, the expression of many paralogous phototransduction genes is partitioned among cone subtypes, analogous to the partitioning of the phototransduction paralogs between rods and cones seen across vertebrates. The partitioned cone-gene pairs arose via the teleost-specific whole-genome duplication or later clade-specific gene duplications. We also discovered that cone subtypes express distinct transcriptional regulators, including many factors not previously implicated in photoreceptor development or differentiation. Overall, our work suggests that partitioning of paralogous gene expression via the action of differentially expressed transcriptional regulators enables diversification of cone subtypes in teleosts.


Assuntos
Perfilação da Expressão Gênica , Regulação da Expressão Gênica , Células Fotorreceptoras de Vertebrados/metabolismo , Animais , Diferenciação Celular , Separação Celular , Análise por Conglomerados , Visão de Cores , Evolução Molecular , Citometria de Fluxo , Redes Reguladoras de Genes , Técnicas Genéticas , Genoma , Proteínas de Fluorescência Verde/metabolismo , Transdução de Sinal Luminoso , RNA-Seq , Retina/metabolismo , Células Fotorreceptoras Retinianas Cones/metabolismo , Células Fotorreceptoras Retinianas Bastonetes/metabolismo , Transcrição Genética , Transcriptoma , Peixe-Zebra
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