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New proline-rich proteins in isolated insect Z-discs.

ABSTRACT: Z-discs were isolated from Lethocerus (waterbug) flight muscle by removing the contractile proteins from myofibrils with a solution of high ionic strength. Sodium dodecyl sulphate (SDS)/polyacrylamide-gel electrophoresis confirmed a previous report that major Z-disc proteins had subunit mol.wts of 200 000, 180 000, 105 000, 95 000, 42 000 and 35 000. A protein of subunit mol.wt 25 000 was found in once-washed Z-discs but was degraded or was removed by successive washes. In addition, a protein of high molecular weight (less than 300 000) was found in Z-discs. Proteins of subunit mol.wts. 42 000, 35 000 and 25 000 were individually sliced from SDS/polyacrylamide gels and eluted. Amino acid analysis showed that the 35 000-subunit-mol.wt. protein was not, as was previously suggested, tropomyosin, but was a distinct Z-disc protein rich in proline. Calculations based on the amino acid analysis showed that this protein contained substantial hydrophobic regions. Preliminary investigations into the isoelectric point and a method of isolation of the 35 000-subunit-mol.wt. Z-disc protein are described. This protein was found in slices cut from SDS/polyacrylamide-gel electrophoretograms of whole myofibrils. The protein of 42 000 subunit mol.wt. was shown by amino acid analysis to be actin and the 25 000-subunit-mol.wt. Z-disc protein was proline-rich.

SUBMITTER: Sainsbury GM

PROVIDER: S-EPMC1162222 | biostudies-other | 1980 Nov

REPOSITORIES: biostudies-other

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Project description:Landscape heterogeneity in floral communities has the potential to modify pollinator behavior. Pollinator foraging varies with the diversity, abundance, and spatial configuration of floral resources. However, the implications of this variation for pollen transfer and ultimately the reproductive success of insect pollinated plants remains unclear, especially for species which are rare or isolated in the landscape. We used a landscape-scale experiment, coupled with microsatellite genotyping, to explore how the floral richness of habitats affected pollinator behavior and pollination effectiveness. Small arrays of the partially self-compatible plant Californian poppy (Eschscholzia californica) were introduced across a landscape gradient to simulate rare, spatially isolated populations. The effects on pollinator activity, outcrossing, and plant reproduction were measured. In florally rich habitats, we found reduced pollen movement between plants, leading to fewer long-distance pollination events, lower plant outcrossing, and a higher incidence of pollen limitation. This pattern indicates a potential reduction in per capita pollinator visitation, as suggested by the lower activity densities and richness of pollinators observed within florally rich habitats. In addition, seed production reduced by a factor of 1.8 in plants within florally rich habitats and progeny germination reduced by a factor of 1.2. We show this to be a consequence of self-fertilization within the partially self-compatible plant, E. californica. These findings indicate that locally rare plants are at a competitive disadvantage within florally rich habitats because neighboring plant species disrupt conspecific mating by co-opting pollinators. Ultimately, this Allee effect may play an important role in determining the long-term persistence of rarer plants in the landscape, both in terms of seed production and viability. Community context therefore requires consideration when designing and implementing conservation management for plants which are comparatively rare in the landscape.

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New proline-rich proteins in isolated insect Z-discs.

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