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White E, Kim S, Wegh G, Chiari Y. Thermal tolerance plasticity and dynamics of thermal tolerance in Eublepharis macularius: Implications for future climate-driven heat stress. J Therm Biol 2024; 123:103912. [PMID: 39024848 DOI: 10.1016/j.jtherbio.2024.103912] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2024] [Revised: 06/02/2024] [Accepted: 06/26/2024] [Indexed: 07/20/2024]
Abstract
The intensity and duration of heat waves, as well as average global temperatures, are expected to increase due to climate change. Heat waves can cause physiological stress and reduce fitness in animals. Species can reduce overheating risk through phenotypic plasticity, which allows them to raise their thermal tolerance limits over time. This mechanism could be important for ectotherms whose body temperatures are directly influenced by available environmental temperatures. Geckos are a large, diverse group of ectotherms that vary in their thermal habitats and times of daily activity, which could affect how they physiologically adjust to heat waves. Data on thermal physiology are scarce for reptiles, with only one study in geckos. Understanding thermal tolerance and plasticity, and their relationship, is essential for understanding how some species are able to adjust or adapt to changing temperatures. In this study, we estimated thermal tolerance and plasticity, and their interaction, in the crepuscular gecko, Eublepharis macularius, a species that is emerging as a model for reptile biology. After estimating basal thermal tolerance for 28 geckos, thermal tolerance was measured for each individual a second time at several timepoints (3, 6, or 24 h) to determine thermal tolerance plasticity. We found that thermal tolerance plasticity (1) does not depend on the basal thermal tolerance of the organism, (2) was highest after 6 h from initial heat shock, and (3) was negatively influenced by individual body mass. Our findings contribute to the increasing body of work focused on understanding the influence of biological and environmental factors on thermal tolerance plasticity in organisms and provide phenotypic data to further investigate the molecular basis of thermal tolerance plasticity in organisms.
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Affiliation(s)
- Emma White
- George Mason University, Department of Biology, Fairfax, VA, USA.
| | - Solyip Kim
- George Mason University, Department of Biology, Fairfax, VA, USA.
| | - Garrett Wegh
- George Mason University, Department of Biology, Fairfax, VA, USA.
| | - Ylenia Chiari
- George Mason University, Department of Biology, Fairfax, VA, USA; University of Nottingham, School of Life Sciences, Nottingham, UK.
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González-Tokman D, Córdoba-Aguilar A, Dáttilo W, Lira-Noriega A, Sánchez-Guillén RA, Villalobos F. Insect responses to heat: physiological mechanisms, evolution and ecological implications in a warming world. Biol Rev Camb Philos Soc 2020; 95:802-821. [PMID: 32035015 DOI: 10.1111/brv.12588] [Citation(s) in RCA: 170] [Impact Index Per Article: 42.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Revised: 01/24/2020] [Accepted: 01/29/2020] [Indexed: 12/12/2022]
Abstract
Surviving changing climate conditions is particularly difficult for organisms such as insects that depend on environmental temperature to regulate their physiological functions. Insects are extremely threatened by global warming, since many do not have enough physiological tolerance even to survive continuous exposure to the current maximum temperatures experienced in their habitats. Here, we review literature on the physiological mechanisms that regulate responses to heat and provide heat tolerance in insects: (i) neuronal mechanisms to detect and respond to heat; (ii) metabolic responses to heat; (iii) thermoregulation; (iv) stress responses to tolerate heat; and (v) hormones that coordinate developmental and behavioural responses at warm temperatures. Our review shows that, apart from the stress response mediated by heat shock proteins, the physiological mechanisms of heat tolerance in insects remain poorly studied. Based on life-history theory, we discuss the costs of heat tolerance and the potential evolutionary mechanisms driving insect adaptations to high temperatures. Some insects may deal with ongoing global warming by the joint action of phenotypic plasticity and genetic adaptation. Plastic responses are limited and may not be by themselves enough to withstand ongoing warming trends. Although the evidence is still scarce and deserves further research in different insect taxa, genetic adaptation to high temperatures may result from rapid evolution. Finally, we emphasize the importance of incorporating physiological information for modelling species distributions and ecological interactions under global warming scenarios. This review identifies several open questions to improve our understanding of how insects respond physiologically to heat and the evolutionary and ecological consequences of those responses. Further lines of research are suggested at the species, order and class levels, with experimental and analytical approaches such as artificial selection, quantitative genetics and comparative analyses.
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Affiliation(s)
- Daniel González-Tokman
- CONACYT, CDMX, 03940, Mexico.,Red de Ecoetología, Instituto de Ecología A. C, Xalapa, 91073, Mexico
| | - Alex Córdoba-Aguilar
- Instituto de Ecología, Universidad Nacional Autónoma de México. Circuito exterior s/n Ciudad Universitaria, CDMX, 04510, Mexico
| | - Wesley Dáttilo
- Red de Ecoetología, Instituto de Ecología A. C, Xalapa, 91073, Mexico
| | - Andrés Lira-Noriega
- CONACYT, CDMX, 03940, Mexico.,Red de Estudios Moleculares Avanzados, Instituto de Ecología A. C, Xalapa, 91073, Mexico
| | | | - Fabricio Villalobos
- Red de Biología Evolutiva, Instituto de Ecología A. C, Xalapa, 91073, Mexico
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Krill JL, Dawson-Scully K. cGMP-Dependent Protein Kinase Inhibition Extends the Upper Temperature Limit of Stimulus-Evoked Calcium Responses in Motoneuronal Boutons of Drosophila melanogaster Larvae. PLoS One 2016; 11:e0164114. [PMID: 27711243 PMCID: PMC5053426 DOI: 10.1371/journal.pone.0164114] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Accepted: 09/20/2016] [Indexed: 12/31/2022] Open
Abstract
While the mammalian brain functions within a very narrow range of oxygen concentrations and temperatures, the fruit fly, Drosophila melanogaster, has employed strategies to deal with a much wider range of acute environmental stressors. The foraging (for) gene encodes the cGMP-dependent protein kinase (PKG), has been shown to regulate thermotolerance in many stress-adapted species, including Drosophila, and could be a potential therapeutic target in the treatment of hyperthermia in mammals. Whereas previous thermotolerance studies have looked at the effects of PKG variation on Drosophila behavior or excitatory postsynaptic potentials at the neuromuscular junction (NMJ), little is known about PKG effects on presynaptic mechanisms. In this study, we characterize presynaptic calcium ([Ca2+]i) dynamics at the Drosophila larval NMJ to determine the effects of high temperature stress on synaptic transmission. We investigated the neuroprotective role of PKG modulation both genetically using RNA interference (RNAi), and pharmacologically, to determine if and how PKG affects presynaptic [Ca2+]i dynamics during hyperthermia. We found that PKG activity modulates presynaptic neuronal Ca2+ responses during acute hyperthermia, where PKG activation makes neurons more sensitive to temperature-induced failure of Ca2+ flux and PKG inhibition confers thermotolerance and maintains normal Ca2+ dynamics under the same conditions. Targeted motoneuronal knockdown of PKG using RNAi demonstrated that decreased PKG expression was sufficient to confer thermoprotection. These results demonstrate that the PKG pathway regulates presynaptic motoneuronal Ca2+ signaling to influence thermotolerance of presynaptic function during acute hyperthermia.
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Affiliation(s)
- Jennifer L. Krill
- Department of Biological Sciences, Florida Atlantic University, Boca Raton, Florida, United States of America
| | - Ken Dawson-Scully
- Department of Biological Sciences, Florida Atlantic University, Boca Raton, Florida, United States of America
- * E-mail:
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Karunanithi S, Brown IR. Heat shock response and homeostatic plasticity. Front Cell Neurosci 2015; 9:68. [PMID: 25814928 PMCID: PMC4357293 DOI: 10.3389/fncel.2015.00068] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Accepted: 02/17/2015] [Indexed: 11/13/2022] Open
Abstract
Heat shock response and homeostatic plasticity are mechanisms that afford functional stability to cells in the face of stress. Each mechanism has been investigated independently, but the link between the two has not been extensively explored. We explore this link. The heat shock response enables cells to adapt to stresses such as high temperature, metabolic stress and reduced oxygen levels. This mechanism results from the production of heat shock proteins (HSPs) which maintain normal cellular functions by counteracting the misfolding of cellular proteins. Homeostatic plasticity enables neurons and their target cells to maintain their activity levels around their respective set points in the face of stress or disturbances. This mechanism results from the recruitment of adaptations at synaptic inputs, or at voltage-gated ion channels. In this perspective, we argue that heat shock triggers homeostatic plasticity through the production of HSPs. We also suggest that homeostatic plasticity is a form of neuroprotection.
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Affiliation(s)
- Shanker Karunanithi
- School of Medical Science, Griffith University QLD, Australia ; Menzies Health Institute of Queensland, Griffith University QLD, Australia
| | - Ian R Brown
- Department of Biological Sciences, Centre for the Neurobiology of Stress, University of Toronto Scarborough Toronto, ON, Canada
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Multifaceted role of heat shock protein 70 in neurons. Mol Neurobiol 2010; 42:114-23. [PMID: 20354811 DOI: 10.1007/s12035-010-8116-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2009] [Accepted: 03/15/2010] [Indexed: 12/22/2022]
Abstract
Heat shock protein 70 (Hsp70) plays important roles in neural protection from stress by assisting cellular protein folding. In this review we discuss the current understanding of inducible and constitutive Hsp70 in maintaining and protecting neuronal synaptic function under normal and stressed conditions.
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Mileva-Seitz V, Xiao C, Seroude L, Robertson RM. Tissue-specific targeting of Hsp26 has no effect on heat resistance of neural function in larval Drosophila. Cell Stress Chaperones 2008; 13:85-95. [PMID: 18347945 PMCID: PMC2666220 DOI: 10.1007/s12192-008-0016-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2007] [Revised: 09/10/2007] [Accepted: 09/11/2007] [Indexed: 11/29/2022] Open
Abstract
Hsp26 belongs to the small heat-shock protein family and is normally expressed in all cells during heat stress. We aimed to determine if overexpression of this protein protects behavior and neural function in Drosophila melanogaster during heat stress, as has previously been shown for Hsp70. We used the UAS-GAL4 expression system to drive expression of Hsp26 in the whole animal (ubiquitously), in the motoneurons, and in the muscles of wandering third-instar larvae. There were slight increases in time to crawling failure and normalized excitatory junction potential (EJP) area for some of the transgenic lines, but these were not consistent. In addition, Hsp26 had no effect on the temperature at failure of EJPs, normalized EJP peak amplitude, and normalized EJP half-width. Overexpression larvae had a similar number of motoneuronal boutons and length of nerve terminals as controls, indicating that the occasional protective effects on locomotion were not due to changes at the synapse. We conclude that overexpression had a small thermoprotective effect on locomotion and no effect on neural function. As it has been shown that Hsp26 requires action of other Hsps to reactivate the denatured proteins to which it binds, we propose that at least in larvae, the function of Hsp26 was masked in the relative absence of other Hsps.
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Affiliation(s)
- Viara Mileva-Seitz
- Department of Biology, Queen’s University, Kingston, ON K7L 3N6 Canada
- Institute of Medical Science, University of Toronto, 7213 Medical Sciences Building, 1 King’s College Circle, Toronto, ON M5S 1A8 Canada
| | - Chengfeng Xiao
- Department of Biology, Queen’s University, Kingston, ON K7L 3N6 Canada
| | - Laurent Seroude
- Department of Biology, Queen’s University, Kingston, ON K7L 3N6 Canada
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Folk DG, Hoekstra LA, Gilchrist GW. Critical thermal maxima in knockdown-selected Drosophila: are thermal endpoints correlated? ACTA ACUST UNITED AC 2007; 210:2649-56. [PMID: 17644679 DOI: 10.1242/jeb.003350] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
To explore the correlation of traits linked to thermotolerance, we compared three thermal endpoints (knockdown temperature and two critical thermal maxima) among replicate populations of Drosophila melanogaster selected for high, or low, knockdown temperature. The high knockdown flies maintain normal posture and locomotor ability within a knockdown column at temperatures >or=40 degrees C, whereas the low knockdown flies fall out of the column at much cooler temperatures (approximately 35 degrees C, on average). The critical thermal maximum (CT(max)) for respiratory control in the selected knockdown populations was determined by analyzing CO(2) output of individuals during exposure to a temperature ramp (from 30 degrees C to >45 degrees C) and was indicated by an abrupt alteration in the pattern of CO(2) release. The CT(max) for locomotor function was determined by monitoring activity (concurrent with CO(2) analysis) during the temperature ramp and was marked by the abrupt cessation of activity. We hypothesized that selection for high knockdown temperature may cause an upward shift in CT(max), whereas selection for low knockdown may lower CT(max). Correlations among the three thermal endpoints varied between the high and low knockdown flies. Finally, we compared metabolic profiles, as well as Q(10) values, among the high and low knockdown males and females during the temperature ramp.
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Affiliation(s)
- Donna G Folk
- Department of Biology, College of William and Mary, Williamsburg, VA 23187, USA.
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