Transverse sections though Drosophila bristles reveal 7-11 nearly round, plasma membrane-associated bundles of actin filaments. These filaments are hexagonally packed and in a longitudinal section they show a 12-nm periodicity in both the 1.1 and 1.0 views. From earlier studies this periodicity is attributable to cross-links and indicates that the filaments are maximally cross-linked, singed mutants also have 7-11 bundles, but the bundles are smaller, flattened, and the filaments within the bundles are randomly packed (not hexagonal); no periodicity can be detected in longitudinal sections. Another mutant, forked (f36a), also has 7-11 bundles but even though the bundles are very small, the filaments within them are hexagonally packed and display a 12-nm periodicity in longitudinal section. The singed-forked double mutant lacks filament bundles. Thus there are at least two species of cross-links between adjacent actin filaments. Hints of why two species of cross-links are necessary can be gleaned by studying bristle formation. Bristles sprout with only microtubules within them. A little later in development actin filaments appear. At early stages the filaments in the bundles are randomly packed. Later the filaments in the bundles become hexagonally packed and maximally cross-linked. We consider that the forked proteins may be necessary early in development to tie the filaments together in a bundle so that they can be subsequently zippered together by fascin (the singed gene product).
Article|
August 01 1995
F actin bundles in Drosophila bristles. I. Two filament cross-links are involved in bundling.
L G Tilney,
L G Tilney
Department of Biology, University of Pennsylvania, Philadelphia 19104, USA.
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M S Tilney,
M S Tilney
Department of Biology, University of Pennsylvania, Philadelphia 19104, USA.
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G M Guild
G M Guild
Department of Biology, University of Pennsylvania, Philadelphia 19104, USA.
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L G Tilney
Department of Biology, University of Pennsylvania, Philadelphia 19104, USA.
M S Tilney
Department of Biology, University of Pennsylvania, Philadelphia 19104, USA.
G M Guild
Department of Biology, University of Pennsylvania, Philadelphia 19104, USA.
Online ISSN: 1540-8140
Print ISSN: 0021-9525
J Cell Biol (1995) 130 (3): 629–638.
Citation
L G Tilney, M S Tilney, G M Guild; F actin bundles in Drosophila bristles. I. Two filament cross-links are involved in bundling.. J Cell Biol 1 August 1995; 130 (3): 629–638. doi: https://doi.org/10.1083/jcb.130.3.629
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