Although it is acknowledged that genetic variation contributes to individual differences in thermotolerance, the specific genes and pathways involved and how they are modulated by the environment remain poorly understood. We link natural variation in the thermotolerance of neural function and behavior in Drosophila melanogaster to the foraging gene (for, which encodes a cGMP-dependent protein kinase (PKG)) as well as to its downstream target, protein phosphatase 2A (PP2A). Genetic and pharmacological manipulations revealed that reduced PKG (or PP2A) activity caused increased thermotolerance of synaptic transmission at the larval neuromuscular junction. Like synaptic transmission, feeding movements were preserved at higher temperatures in larvae with lower PKG levels. In a comparative assay, pharmacological manipulations altering thermotolerance in a central circuit of Locusta migratoria demonstrated conservation of this neuroprotective pathway. In this circuit, either the inhibition of PKG or PP2A induced robust thermotolerance of neural function. We suggest that PKG and therefore the polymorphism associated with the allelic variation in for may provide populations with natural variation in heat stress tolerance. for's function in behavior is conserved across most organisms, including ants, bees, nematodes, and mammals. PKG's role in thermotolerance may also apply to these and other species. Natural variation in thermotolerance arising from genes involved in the PKG pathway could impact the evolution of thermotolerance in natural populations.
References
[1]
Guschina IA, Harwood JL (2006) Mechanisms of temperature adaptation in poikilotherms. FEBS 580: 5477.
[2]
Rinehart JP, Hayward S, Elnitsky MA, Sandro L, Lee R Jr, et al. (2006) Continuous up-regulation of heat shock proteins in larvae, but not adults, of a polar insect. Proc Natl Acad Sci USA 103: 14223.
[3]
Hazel JR (1995) Thermal adaptation in biological membranes: is homeoviscous adaptation the explanation? Annu Rev Physiol 57: 19.
[4]
Newman AEM, Foerster M, Shoemaker KL, Robertson RM (2003) Stress-induced thermotolerance of ventilatory motor pattern generation in the locust, Locusta migratoria. J Insect Physiol 49: 1039.
[5]
Bressin S, Willmer PG (2000) Estimation of thermal constants: the importance of using equilibrium temperature rather than ambient temperature demonstrated with hoverflies (Diptera, Syrphidae, genus Eristalis). J Exp Biol 203: 2511.
[6]
Spiewok S, Schmolz E (2006) Changes in temperature and light alter the flight speed of hornets (Vespa crabro L.). Physiol Biochem Zool 79: 188.
[7]
Glazer JL (2005) Management of heatstroke and heat exhaustion. Am Fam Physician 71: 11 2133.
[8]
Bouchama A, Knochel JP (2002) Heat stroke. N Engl J Med 346: 1978.
Feder ME (1997) Necrotic fruit: a novel model system for thermal biologists. J Therm Biol 22: 1.
[11]
Osborne KA, Robichon A, Burgess E, Butland S, Shaw RA, et al. (1997) Natural behavior polymorphism due to a cGMP-dependent protein kinase of Drosophila. Science 277: 834.
[12]
de Belle JS, Sokolowski MB, Hilliker AJ (1989) Genetic localization of foraging (for): a major gene for larval behavior in Drosophila melanogaster. Genetics 123: 157.
[13]
Renger JJ, Yao WD, Sokolowski MB, Wu CF (1999) Neuronal polymorphism among natural alleles of a cGMP-dependent kinase gene, foraging, in Drosophila. J Neurosci 19: RC28.
[14]
Ramirez JM, Elsen FP, Robertson RM (1999) Long-term effects of prior heat shock on neuronal potassium currents recorded in a novel insect ganglion slice preparation. J Neurophysiol 81: 795.
Zhou XB, Ruth P, Schlossmann J, Hofmann F, Korth M (1996) Protein phosphatase 2A is essential for the activation of Ca2+-activated K+ currents by cGMP-dependent protein kinase in tracheal smooth muscle and Chinese hamster ovary cells. J Biol Chem 271(33): 19760.
[17]
White RE, Han G, Maunz M, Dimitropoulou C, El-Mowafy AM, et al. (2002) Endothelium-independent effect of estrogen on Ca(2+)-activated K(+) channels in human coronary artery smooth muscle cells. Cardiovasc Res 53(3): 650.
[18]
Dawson-Scully K, Robertson RM (1998) Heat shock protects synaptic transmission in flight motor circuitry of locusts. Neuroreport 9: 2589.
[19]
Armstrong GA, Shoemaker KL, Money TG, Robertson RM (2006) Octopamine mediates thermal preconditioning of the locust ventilatory central pattern generator via a cAMP/protein kinase A signaling pathway. J Neurosci 26(47): 12118.
[20]
Karunanithi S, Barclay JW, Robertson RM, Brown IR, Atwood HL (1999) Neuroprotection at Drosophila synapses conferred by prior heat shock. J Neurosci 19: 4360.
[21]
Wang HD, Kazemi-Esfarjani P, Benzer S (2004) Multiple-stress analysis for isolation of Drosophila longevity genes. Proc Natl Acad Sci USA 101: 12610.
[22]
Cairns J, Qin S, Philp R, Tan YH, Guy GR (1994) Dephosphorylation of the small heat shock protein Hsp27 in vivo by protein phosphatase 2A. J Biol Chem 269: 9176.
[23]
Whyard S, Wyatt G, Walker VK (1986) The heat shock response in Locusta migratoria. J Comp Physiol B 156: 813.
[24]
Sokolowski MB, Carton Y (1990) Microgeographic variation in Drosophila melanogaster larval behavior. J Insect Behav 2: 829.
[25]
de Belle JS, Sokolowski MB (1987) Heredity of rover/sitter: Alternative foraging strategies of Drosophila melanogaster. Heredity 59: 73.
[26]
P？rtner HO, Knust R (2007) Climate change affects marine fishes through the oxygen limitation of thermal tolerance. Science 315: 5808, 95:
[27]
Pereira HS, Sokolowski MB (1993) Mutations in the larval foraging gene affect adult locomotory behavior after feeding in Drosophila melanogaster. Proc Natl Acad Sci USA 90: 5044.
[28]
Macleod GT, Hegstrom-Wojtowicz M, Charlton MP, Atwood HL (2003) Fast calcium signals in Drosophila motor neuron terminals. J Neurophysiol 88(5): 2659.
[29]
Grider JR (1993) Interplay of VIP and nitric oxide in regulation of the descending relaxation phase of peristalsis. Am J Physiol 264: G334–G340.
[30]
Kase H, Iwahashi K, Nakanishi S, Matsuda Y, Yamada K, et al. (1987) K-252 compounds, novel and potent inhibitors of protein kinase C and cyclic nucleotide-dependent protein kinases. Biochem Biophys Res Comm 142: 436–440.
[31]
Li YM, Casida JE (1992) Cantharidin-binding protein: identification as protein phosphatase 2A. Proc Natl Acad Sci USA 89: 11867–11870.
[32]
Rothermel JD, Parker Botelho LH (1988) A mechanistic and kinetic analysis of the interactions of the diastereoisomers of adenosine 3′,5′-(cyclic)phosphorothioate with purified cyclic AMP-dependent protein kinase. Biochem J 251: 757–762.
[33]
Li YM, Mackintosh C, Casida JE (1993) Protein phosphatase 2A and its [3H]cantharidin/[3H]endothall thioanhydride binding site. Inhibitor specificity of cantharidin and ATP analogues. Biochem Pharmacol 46: 1435.
[34]
Graziano MJ, Pessah IN, Matsuzawa M, Casida JE (1988) Partial characterization of specific cantharidin binding sites in mouse tissues. Mol Pharmacol 6: 706–12.
