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An ultrastructural analysis of the ecdysoneless (1(3)ecd1ts) ring gland during the third larval instar of Drosophila melanogaster

UNCG Author/Contributor (non-UNCG co-authors, if there are any, appear on document)
Vincent C. Henrich, Professor (Creator)
Institution
The University of North Carolina at Greensboro (UNCG )
Web Site: http://library.uncg.edu/

Abstract: In the late third larval instar of Drosophila melanogaster, the prothoracic gland, an endocrine portion of the ring gland, synthesizes ecdysteroids at an accelerated rate. The resultant ecdysteroid titer peak initiates the events associated with metamorphosis. The normal prothoracic gland displays several ultrastructural features at this developmental stage that reflect increased steroidogenic activity, including extensive infoldings of the plasma membrane (membrane invaginations) and an increase in both the concentration of smooth endoplasmic reticulum (SER) (or transitional ER) and elongated mitochondria. By contrast, the prothoracic glands of larvae homozygous for a conditional larval lethal mutation, l(3)ecd1ts, not only fail to produce ecdysteroids at normal levels at the restrictive temperature (29° C), but also acquire abnormal morphological features that reflect the disruptive effects of the mutation. These abnormalities include an accumulation of lipid droplets presumed to contain sterol precursors of ecdysteroids, a disappearance of SER and a drastic reduction of membrane invaginations in the peripheral area of the cell. These morphological defects are observed in pro- thoracic glands dissected from larvae transferred from 18° C to 29° C approximately 24 h before observation and also within 4 h of an in vitro transfer to 29° C following dissection from wandering third instar larvae reared at 18° C. No ultrastructural abnormalities were noted in the corpus allatum portion of mutant ring glands. These observations further indicate the direct involvement of the ecd gene product in ecdysteroid synthesis and suggest a role for the gene in the proper transport of precursors to the site where they can be utilized in ecdysteroid biosynthesis.

Additional Information

Publication
Cell and Tissue Research
Language: English
Date: 1991
Keywords
Prothoracic gland, Ecdysteroid, Corpus allatum, Juvenile hormone, Drosophila melanogaster (Insecta)