Nathan Rank

Sonoma State University

Local adaptation in montane leaf beetles
Environmental Gradients and Stress Proteins (Page 3 of 4)

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Enzyme polymorphisms

Environmental Gradients & Stress Proteins

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See also research summary.
Evidence for environmental variation and for thermal physiological responses to it.

  • The northern drainage Rock Creek is cooler than Bishop Creek or Big Pine Creek
  • Air temperature decreases as elevation increases.
  • Chrysomela aeneicollis body temperatures track air temperatures closely. Thus, beetles cannot behaviorally thermoregulate well enough to avoid habitat temperature variation..
  • Levels of heat shock proteins differ among beetle populations living in different environments.
    • BPC beetles contain higher levels of the consitutive stress protein HSC70.
    • RC beetles contained higher levels of the inducible form HSP72.

Mean air temperatures in three drainages over six weeks

Air temperature differences among drainages

  • We placed dataloggers in 5 localities per drainage (2800-3300m) in June 1998.
  • The northern drainage RC is cooler than BC or BPC.
  • Air temperature decreases with elevation

Heat shock protein levels differ among beetle populations in different environments

  • To cope with heat stress, many organisms produce heat shock proteins.
    • Heat shock proteins interact with other enzyme molecules and thereby 'protect' the enzymes from heat denaturation.
    • Some heat shock proteins are continuously produced (constitutive). Others are induced in response to heat stress.
  • The blot shown below shows that two stress proteins were assayed in C. aeneicollis.
    • All 180 beetles expressed measurable amounts of the consitutive protein HSC73.
    • Eleven beetles expressed the inducible protein HSP72 (e.g. RC8 in the blot below).

One of 44 experimental blots taken from gels from 180 beetles. Two samples were run per beetle and different numbers represent different beetles. Gels were run in the laboratory of Prof. Elizabeth Dahlhoff

Results of stress protein analsysis

  • Beetles from BPC expressed more HSC73 than those from BC or RC
  • Beetles from high elevation populations produced less HSC73 than those from low elevation populations.
  • Beetles from the coolest drainage RC produced more of the inducible heat shock protein HSP72.

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January 23, 1999 NER