QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

Help viewing high resolution images Return to article

Fig. 5. Ultrastructural analysis of mutant phenotypes. Schematic representations of wild-type cuticle (A) or muscle-attachment sites (B) of late Drosophila embryos (about 21 hours) and micrographs of these structures in wild-type and mutant embryos (C-F"). Symbols and abbreviations are used consistently throughout: aj or white arrow, apical junctions; at or curved white arrows, apical transverse filaments; ch, chitin layer; cu, trilaminar cuticulin layer; dz or black arrowheads, deposition zone; ed, epidermal cell; el, electron-lucent layer; en or asterisk, endocuticle; ep or black dot, epicuticle; es, extracellular space; mt or white arrowhead, microtubules; mtj or curved black arrow, myotendinous junction; mu, muscle; nu, nucleus; pe, fibrillar protein epicuticle; tf or white chevron, tonofilament; tn, tendon cell. [Nomenclature according to Kaznowski et al. (Kaznowski et al., 1985) and Tepass and Hartenstein (Tepass and Hartenstein, 1994).] The characteristic arrangement of the epicuticle (black dots) and the typical occurrence of the darker cuticular deposition zone (dz), which associates with epidermal microvilli (mv), can be seen in wild-type (A-C"), pio^V132 (D,D'), pot^P14 (E,E') and dp^1v1 (F,F') mutant embryos alike. Typical features of epidermal tendon cells (tn) are their pronounced basal junctions with muscles (curved black arrows) and apical junctions (white arrows) adhering to tonofilaments (white chevrons) that anchor in the cuticle. Apical and basal junctions of tendon cells are intracellularly connected via microtubules (white arrowheads). These characteristic features of wild-type embryos (B,C") seem unaffected in pot^P14, pio^V132 and dp^1v1 mutant embryos (D"-F"), although they are difficult to find and interpret owing to epidermal detachment from the cuticle. The main defect of pot^P14, pio^V132 and dp^1v1 mutant embryos consists in a disruption of the chitin layer (ch) of the endocuticle (asterisks), leading to a separation of deposition zone and epicuticle (D-F,D'-F'), and failure of tonofilaments to anchor in the cuticle (D",F", white chevrons). Bar, 0.5 µm (left and right columns, C-F,C"-F"), 0.2 µm (middle column, C'-F').

Return to article