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Molecular Biology and Evolution Feb 2024Rainforest hunter-gatherers from Southeast Asia are characterized by specific morphological features including a particularly dark skin color (D), short stature (S),...
Rainforest hunter-gatherers from Southeast Asia are characterized by specific morphological features including a particularly dark skin color (D), short stature (S), woolly hair (W), and the presence of steatopygia (S)-fat accumulation localized in the hips (DSWS phenotype). Based on previous evidence in the Andamanese population, we first characterized signatures of adaptive natural selection around the calcium-sensing receptor gene in Southeast Asian rainforest groups presenting the DSWS phenotype and identified the R990G substitution (rs1042636) as a putative adaptive variant for experimental follow-up. Although the calcium-sensing receptor has a critical role in calcium homeostasis by directly regulating the parathyroid hormone secretion, it is expressed in different tissues and has been described to be involved in many biological functions. Previous works have also characterized the R990G substitution as an activating polymorphism of the calcium-sensing receptor associated with hypocalcemia. Therefore, we generated a knock-in mouse for this substitution and investigated organismal phenotypes that could have become adaptive in rainforest hunter-gatherers from Southeast Asia. Interestingly, we found that mouse homozygous for the derived allele show not only lower serum calcium concentration but also greater body weight and fat accumulation, probably because of enhanced preadipocyte differentiation and lipolysis impairment resulting from the calcium-sensing receptor activation mediated by R990G. We speculate that such differential features in humans could have facilitated the survival of hunter-gatherer groups during periods of nutritional stress in the challenging conditions of the Southeast Asian tropical rainforests.
Topics: Animals; Humans; Mice; Calcium; Phenotype; Polymorphism, Genetic; Receptors, Calcium-Sensing; Selection, Genetic
PubMed: 38285634
DOI: 10.1093/molbev/msae015 -
Plants (Basel, Switzerland) Jan 2024Brassinosteroids (BRs) represent a group of plant signaling molecules with a steroidal skeleton that play an essential role in plant adaptation to different...
Brassinosteroids (BRs) represent a group of plant signaling molecules with a steroidal skeleton that play an essential role in plant adaptation to different environmental stresses, including drought. In this work, the effect of pretreatment with 0.4 µM 24-epibrassinolide (EBR) on the oxidant/antioxidant system in 4-day-old wheat seedlings ( L.) was studied under moderate drought stress simulated by 12% polyethylene glycol 6000 (PEG). It was revealed that EBR-pretreatment had a protective effect on wheat plants as evidenced by the maintenance of their growth rate, as well as the reduction in lipid peroxidation and electrolyte leakage from plant tissues under drought conditions. This effect was likely due to the ability of EBR to reduce the stress-induced accumulation of reactive oxygen species (ROS) and modulate the activity of antioxidant enzymes. Meanwhile, EBR pretreatment enhanced proline accumulation and increased the barrier properties of the cell walls in seedlings by accelerating the lignin deposition. Moreover, the ability of EBR to prevent a drought-caused increase in the intensity of the total dark respiration and the capacity of alternative respiration contributes significantly to the antistress action of this hormone.
PubMed: 38256702
DOI: 10.3390/plants13020148 -
Molecular Biology and Evolution Feb 2024Local adaptation is critical in speciation and evolution, yet comprehensive studies on proximate and ultimate causes of local adaptation are generally scarce. Here, we...
Local adaptation is critical in speciation and evolution, yet comprehensive studies on proximate and ultimate causes of local adaptation are generally scarce. Here, we integrated field ecological experiments, genome sequencing, and genetic verification to demonstrate both driving forces and molecular mechanisms governing local adaptation of body coloration in a lizard from the Qinghai-Tibet Plateau. We found dark lizards from the cold meadow population had lower spectrum reflectance but higher melanin contents than light counterparts from the warm dune population. Additionally, the colorations of both dark and light lizards facilitated the camouflage and thermoregulation in their respective microhabitat simultaneously. More importantly, by genome resequencing analysis, we detected a novel mutation in Tyrp1 that underpinned this color adaptation. The allele frequencies at the site of SNP 459# in the gene of Tyrp1 are 22.22% G/C and 77.78% C/C in dark lizards and 100% G/G in light lizards. Model-predicted structure and catalytic activity showed that this mutation increased structure flexibility and catalytic activity in enzyme TYRP1, and thereby facilitated the generation of eumelanin in dark lizards. The function of the mutation in Tyrp1 was further verified by more melanin contents and darker coloration detected in the zebrafish injected with the genotype of Tyrp1 from dark lizards. Therefore, our study demonstrates that a novel mutation of a major melanin-generating gene underpins skin color variation co-selected by camouflage and thermoregulation in a lizard. The resulting strong selection may reinforce adaptive genetic divergence and enable the persistence of adjacent populations with distinct body coloration.
Topics: Animals; Melanins; Lizards; Zebrafish; Body Temperature Regulation; Skin Pigmentation; Color
PubMed: 38243850
DOI: 10.1093/molbev/msae009 -
Royal Society Open Science Jan 2024Many animals show an aversion to bright, open spaces, with significant variability seen across species, populations and individuals within populations. Although there is...
Many animals show an aversion to bright, open spaces, with significant variability seen across species, populations and individuals within populations. Although there is much interest in the underlying causes of this behaviour, few studies have been able to systematically isolate the role of heritable and environmental effects. Here, we addressed this gap using a common garden experiment with cavefish. Specifically, we bred and cross-bred cave loaches (), Europe's only known cavefish, in the laboratory, raised the offspring in complete darkness or normal light conditions, and studied their light avoidance behaviour. Cavefish spent much more time in a light area and ventured further out, while surface fish spent considerable time in risk-assessment behaviour between the light and dark areas. Hybrids behaved most similarly to cavefish. Light treatment and eye quality and lens size only had a modest effect. Our results suggest light avoidance behaviour of cavefish has a heritable basis and is fundamentally linked to increased boldness rather than reduced vision, which is likely adaptive given the complete lack of macropredators in the cave environment. Our study provides novel experimental insights into the behavioural divergence of cavefish and contributes to our broader understanding of the evolution of boldness and behavioural adaptation.
PubMed: 38204784
DOI: 10.1098/rsos.231517 -
Scientific Reports Jan 2024A study was conducted with 115 subjects who regularly drove at night to validate a refraction protocol for detecting refractive visual changes from daytime to nighttime...
A study was conducted with 115 subjects who regularly drove at night to validate a refraction protocol for detecting refractive visual changes from daytime to nighttime conditions. Objective and subjective refractions were performed in both photopic and mesopic conditions, with a dark adaptation period before the mesopic subjective refraction. The results showed that in mesopic conditions, visual acuity decreased by 0.2 logMAR units on average (p < 0.01), and there was a myopic refractive shift of - 0.36 ± 0.20 D (p < 0.01). Most subjects (92.2%) exhibited a myopic refractive shift of at least 0.12 D. Compensation of refractive shift improved mesopic visual acuity by 0.06 logMAR on average (p < 0.01) and higher refractive shifts showed higher improvement. Night Rx was preferred by 82.1% of subjects with myopic refractive shift. Gender and age did not significantly affect the refractive shift, although myopes showed a higher shift compared to emmetropes (p < 0.01). The refractive shift remained stable over time when the time slot of the day did not change (p < 0.01). Night Rx protocol proved to be a robust and accurate method for identifying drivers with refractive changes when transitioning from photopic to mesopic conditions. The high prevalence and inter-individual variability of Rx shift highlight the need of customized refraction.
Topics: Humans; Myopia; Visual Acuity; Refraction, Ocular; Vision Tests; Emmetropia
PubMed: 38168766
DOI: 10.1038/s41598-023-51062-8 -
Zoological Letters Jan 2024Egg-laying mammals (monotremes) are considered "primitive" due to traits such as oviparity, cloaca, and incomplete homeothermy, all of which they share with reptiles....
Egg-laying mammals (monotremes) are considered "primitive" due to traits such as oviparity, cloaca, and incomplete homeothermy, all of which they share with reptiles. Two groups of monotremes, the terrestrial echidna (Tachyglossidae) and semiaquatic platypus (Ornithorhynchidae), have evolved highly divergent characters since their emergence in the Cenozoic era. These evolutionary differences, notably including distinct electrosensory and chemosensory systems, result from adaptations to species-specific habitat conditions. To date, very few studies have examined the visual adaptation of echidna and platypus. In the present study, we show that echidna and platypus have different light absorption spectra in their dichromatic visual sensory systems at the molecular level. We analyzed absorption spectra of monotreme color opsins, long-wavelength sensitive opsin (LWS) and short-wavelength sensitive opsin 2 (SWS2). The wavelength of maximum absorbance (λ) in LWS was 570.2 in short-beaked echidna (Tachyglossus aculeatus) and 560.6 nm in platypus (Ornithorhynchus anatinus); in SWS2, λ was 451.7 and 442.6 nm, respectively. Thus, the spectral range in echidna color vision is ~ 10 nm longer overall than in platypus. Natural selection analysis showed that the molecular evolution of monotreme color opsins is generally functionally conserved, suggesting that these taxa rely on species-specific color vision. In order to understand the usage of color vision in monotremes, we made 24-h behavioral observations of captive echidnas at warm temperatures and analyzed the resultant ethograms. Echidnas showed cathemeral activity and various behavioral repertoires such as feeding, traveling, digging, and self-grooming without light/dark environment selectivity. Halting (careful) behavior is more frequent in dark conditions, which suggests that echidnas may be more dependent on vision during the day and olfaction at night. Color vision functions have contributed to dynamic adaptations and dramatic ecological changes during the ~ 60 million years of divergent monotreme evolution. The ethogram of various day and night behaviors in captive echidnas also contributes information relevant to habitat conservation and animal welfare in this iconic species, which is locally endangered.
PubMed: 38167154
DOI: 10.1186/s40851-023-00224-7 -
Translational Vision Science &... Dec 2023The purpose of this study was to establish and validate a novel fundus-controlled dark-adaptometry method.
PURPOSE
The purpose of this study was to establish and validate a novel fundus-controlled dark-adaptometry method.
METHODS
We developed a custom dark-adaptometry software for the S-MAIA device using the open-perimetry-interface. In the validation-substudy, participants underwent dark-adaptometry testing with a comparator device (MonCvONE, 59% rhodopsin bleach, cyan and red stimuli centered at 2 degrees, 4 degrees, and 6 degrees eccentricity). Following a brief break (approximately 5 minutes), the participants were bleached again and underwent dark-adaptometry testing with the S-MAIA device (same loci). In the retest reliability-substudy, participants were tested twice with the S-MAIA device (same loci as above). Nonlinear curve fitting was applied to extract dark-adaptation curve parameters. Validity and repeatability were summarized in terms of the mean bias and 95% limits of agreement (LoAs).
RESULTS
In the validation-substudy (N = 20 participants, median age interquartile range [IQR] 31.5 years [IQR = 25.8, 62.0]), measures of rod-mediated dark-adaptation showed little to no between method differences for the cone-rod-break-time (bias 95% confidence interval [95% CI] of +0.1 minutes [95% CI = -0.6 to 0.8]), rod-intercept-time (-0.23 minutes [95% CI = -1.38 to 0.93]), and S2 slope (-0.01 LogUnits/minutes [95% CI = -0.02 to -0.01]). In the retest reliability-substudy (N = 10 participants, 32.0 years [95% CI = 27.0, 57.5]), the corresponding LoAs were (cone-rod-break-time) -3.94 to 2.78 minutes, (rod-intercept-time) -4.55 to 3.11 minutes, and (S2 slope [rate-limited component of rod recovery]) -0.03 to 0.03 LogUnits/minutes. The LoAs for the steady-state cone and rod thresholds were -0.28 to 0.33 LogUnits and -0.34 to 0.28 LogUnits.
CONCLUSIONS
The devised fundus-controlled dark-adaptometry method yields valid and reliable results.
TRANSLATIONAL RELEVANCE
Fundus-controlled dark-adaptometry solves the critical need for localized testing of the visual cycle and retinoid transfer in eyes with unstable fixation.
Topics: Humans; Adult; Retinal Rod Photoreceptor Cells; Reproducibility of Results; Dark Adaptation; Fundus Oculi; Retinal Cone Photoreceptor Cells
PubMed: 38112496
DOI: 10.1167/tvst.12.12.18 -
BMC Biology Dec 2023Rhabdomeric photoreceptors of eyes in the terrestrial slug Limax are the typical invertebrate-type but unique in that three visual opsins (Gq-coupled rhodopsin,...
BACKGROUND
Rhabdomeric photoreceptors of eyes in the terrestrial slug Limax are the typical invertebrate-type but unique in that three visual opsins (Gq-coupled rhodopsin, xenopsin, Opn5A) and one retinochrome, all belonging to different groups, are co-expressed. However, molecular properties including spectral sensitivity and G protein selectivity of any of them are not determined, which prevents us from understanding an advantage of multiplicity of opsin properties in a single rhabdomeric photoreceptor. To gain insight into the functional role of the co-expression of multiple opsin species in a photoreceptor, we investigated the molecular properties of the visual opsins in the present study.
RESULTS
First, we found that the fourth member of visual opsins, Opn5B, is also co-expressed in the rhabdomere of the photoreceptor together with previously identified three opsins. The photoreceptors were also demonstrated to express Gq and Go alpha subunits. We then determined the spectral sensitivity of the four visual opsins using biochemical and spectroscopic methods. Gq-coupled rhodopsin and xenopsin exhibit maximum sensitivity at ~ 456 and 475 nm, respectively, and Opn5A and Opn5B exhibit maximum sensitivity at ~ 500 and 470 nm, respectively, with significant UV sensitivity. Notably, in vitro experiments revealed that Go alpha was activated by all four visual opsins, in contrast to the specific activation of Gq alpha by Gq-coupled rhodopsin, suggesting that the eye photoreceptor of Limax uses complex G protein signaling pathways.
CONCLUSIONS
The eye photoreceptor in Limax expresses as many as four different visual opsin species belonging to three distinct classes. The combination of opsins with different spectral sensitivities and G protein selectivities may underlie physiological properties of the ocular photoreception, such as a shift in spectral sensitivity between dark- and light-adapted states. This may be allowed by adjustment of the relative contribution of the four opsins without neural networks, enabling a simple strategy for fine-tuning of vision.
Topics: Animals; Opsins; Photoreceptor Cells, Invertebrate; Rhodopsin; Mollusca; GTP-Binding Proteins
PubMed: 38110917
DOI: 10.1186/s12915-023-01789-7 -
ELife Dec 2023Habituation allows animals to learn to ignore persistent but inconsequential stimuli. Despite being the most basic form of learning, a consensus model on the underlying...
Habituation allows animals to learn to ignore persistent but inconsequential stimuli. Despite being the most basic form of learning, a consensus model on the underlying mechanisms has yet to emerge. To probe relevant mechanisms, we took advantage of a visual habituation paradigm in larval zebrafish, where larvae reduce their reactions to abrupt global dimming (a dark flash). We used Ca imaging during repeated dark flashes and identified 12 functional classes of neurons that differ based on their rate of adaptation, stimulus response shape, and anatomical location. While most classes of neurons depressed their responses to repeated stimuli, we identified populations that did not adapt or that potentiated their response. These neurons were distributed across brain areas, consistent with a distributed learning process. Using a small-molecule screening approach, we confirmed that habituation manifests from multiple distinct molecular mechanisms, and we have implicated molecular pathways in habituation, including melatonin, oestrogen, and GABA signalling. However, by combining anatomical analyses and pharmacological manipulations with Ca imaging, we failed to identify a simple relationship between pharmacology, altered activity patterns, and habituation behaviour. Collectively, our work indicates that habituation occurs via a complex and distributed plasticity processes that cannot be captured by a simple model. Therefore, untangling the mechanisms of habituation will likely require dedicated approaches aimed at sub-component mechanisms underlying this multidimensional learning process.
Topics: Animals; Larva; Zebrafish; Spatial Learning; Brain; Consensus; Perciformes
PubMed: 38108818
DOI: 10.7554/eLife.84926 -
Frontiers in Physiology 2023Light traps have been widely used to monitor and manage pest populations, but natural enemies are also influenced. The Fairmaire is an important species of natural...
Light traps have been widely used to monitor and manage pest populations, but natural enemies are also influenced. The Fairmaire is an important species of natural enemy for longhorn beetles. However, the molecular mechanism of in response to light exposure is still scarce. Here, integrated behavioral, comparative transcriptome and weighted gene co-expression network analyses were applied to investigate gene expression profiles in the head of at different light exposure time. The results showed that the phototactic response rates of adults were 1.67%-22.5% and females and males displayed a negative phototaxis under different light exposure [6.31 × 10 (photos/m/s)]; the trapping rates of female and male were influenced significantly by light exposure time, diel rhythm, and light wavelength in the behavioral data. Furthermore, transcriptome data showed that a total of 1,052 significantly differentially expressed genes (DEGs) were identified under different light exposure times relative to dark adaptation. Bioinformatics analyses revealed that the "ECM-receptor interaction," "focal adhesion," "PI3K-Akt signaling," and "lysosome" pathways were significantly downregulated with increasing light exposure time. Furthermore, nine DEGs were identified as hub genes using WGCNA analysis. The results revealed molecular mechanism in negative phototactic behavior response of under the light exposure with relative high intensity, and provided valuable insights into the underlying molecular response mechanism of nocturnal beetles to light stress.
PubMed: 38107477
DOI: 10.3389/fphys.2023.1250836