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First published online November 30, 2007
Journal of Experimental Biology 210, 4298-4306 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.011114
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Parasites, proteomics and performance: effects of gregarine gut parasites on dragonfly flight muscle composition and function

Rudolf J. Schilder* and James H. Marden

Department of Biology, 208 Mueller Lab, Pennsylvania State University, University Park, PA 16802, USA


Figure 1
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  		Fig. 1. Representative 2-D PAGE gels showing muscle protein expression in healthy and infected individuals. Lower panels highlighting spots of interest in areas `a' (Spot 6) and `b' (TnT Spots 1–5). Vertical dimension markers represent molecular mass (in kDa) markers added to the gel; horizontal dimension markers indicate pH range.

 

Figure 2
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  		Fig. 2. (A) 3-D structure model of Drosophila melanogaster MHC head region (i.e. incomplete MHC), showing theoretical calpain digestion sites (marked as red and blue spheres). Regions that would be excluded from Spot 6 due to digestion by calpain are shown in grey. (B) Protein sequence alignment for three insect species of MHC head region in which theoretical calpain digestion sites are located. One such site (Lys560–Ser561) is present for the mosquito Anopheles gambiae (A. gam), while both sites are present for the fruitfly Drosophila melanogaster (D. mel) and honey bee Apis mellifera (Ap. mel; Lys561–Ser562 and Lys613–Ser614, respectively).

 

Figure 3
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  		Fig. 3. (A) Western blot on muscle homogenates enriched in myofibrillar proteins from infected (i) and healthy (h) individuals, probed with a monoclonal antibody to Drosophila MHC. Lanes contain identical protein concentrations. Aside from the 206 kDa muscle MHC and non-specific reactivity to some high-molecular-mass proteins, a 165 and 155 kDa protein were identified. Left tick marks represent molecular mass standards (lane not shown). The presence of 165 and 155 kDa bands in infected muscle indicates that this may be a relatively `high-powered' infected individual, as shown in Fig. 5E. However, no performance measures were obtained from this individual's muscles. (B) Silver-stained SDS-PAGE gel showing peptides obtained by calpain (lane b) digestion of purified L. pulchella MHC from both healthy and infected individuals (lane a). In calpain-treated samples, a 156 kDa peptide can be observed, as well as a 122 and 110 kDa peptide. In addition, we putatively identified a calpain 80 kDa subunit, and other bands as calpain autodegradation products [i.e. similar to results reported by Pemrick and Grebenau (Pemrick and Grebenau, 1984Go)].

 

Figure 4
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  		Fig. 4. Quantitative variation in MHC155 abundance and the first principal component (PC1) of TnT isoform composition in flight muscles of healthy (N=6) and infected (N=11) dragonflies. Upper panels highlight comparisons for (A) MHC155 and (B) TnT spots between healthy and infected individuals. Lower panels show comparison of mean values of log10 %MHC155 and PC1 TnT. Error bars represent standard deviation from means.

 

Figure 5
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  		Fig. 5. Relationships between muscle power output (W kg–1) and (A) log10 %MHC155 (r2=0.85) and (B) PC1 TnT (r2=0.79) obtained from principal component analysis of five TnT spot quantities for healthy dragonflies (open circles, N=6). (C,D) No significant relationships between muscle power output and MHC155 and PC1 TnT values were found for infected individuals (filled circles, N=11). Relationships between muscle power output and (E) log10 %MHC155 [muscle power output= 159.05506 + 16.421664(log10%MHC155) – 55.997116(log10%MHC155 – 0.2526)2] and (F) PC1 TnT [muscle power output=139.5–14.6(PC1TnT)] for healthy (open circles) and infected (filled circles) individuals combined.

 

Figure 6
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  		Fig. 6. Results of multiple linear regression of muscle power output (W kg–1) and the two predictor variables log10 %MHC155 and PC1 TnT (see also Table 1), showing the relationship between actual muscle power output and that predicted by the two parameter model (adjusted r2=0.979, P=0.001, N=6) for healthy individuals (A). The same model explains only 38.3% (adjusted r2=0.295, P=0.034, N=17) of the variation in muscle power output when data for infected individuals (filled circles) are included (B).

 




© The Company of Biologists Ltd 2007