Development of DNA puffs and patterns of polypeptide synthesis in the salivary glands of Bradysia hygida

In the three salivary gland regions of Bradysia hygida (Diptera, Sciaridae) the patterns of polypeptide synthesis, as revealed by electrophoresis and fluorography, are very stable during the fourth larval instar until about 30 h before the pupal molt. At this age the patterns of polypeptide synthesis start to undergo marked changes. The striking correlations between these changes and the development of two distinct groups of DNA puffs support the proposal that DNA puffs are causally related to the synthesis of specific proteins in the salivary glands.

5-Bromo-2'-deoxyuridine induces visible morphological alteration in the DNA puffs of the anterior salivary gland region of Bradysia hygida (Diptera, Sciaridae)

5-Bromo-2'-deoxyuridine (BrdUrd) has long been known to interfere with cell differentiation. We found that treatment of Bradysia hygida larvae with BrdUrd during DNA puff anlage formation in the polytene chromosomes of the salivary gland S1 region noticeably affects anlage morphology. However, it does not affect subsequent metamorphosis to the adult stage. The chromatin of the chromosomal sites that would normally form DNA puffs remains very compact and DNA puff expansion does not occur with administration of 4 to 8 mM BrdUrd. Injection of BrdUrd at different ages provoked a gradient of compaction of the DNA puff chromatin, leading to the formation of very small to almost normal puffs. By immunodetection, we show that the analogue is preferentially incorporated into the DNA puff anlages. When BrdUrd is injected in a mixture with thymidine, it is not incorporated into the DNA, and normal DNA puffs form. Therefore, incorporation of this analogue into the amplified DNA seems to be the cause of this extreme compaction. Autoradiographic experiments and silver grains counting showed that this treatment decreases the efficiency of RNA synthesis at DNA puff anlages.

The Feulgen reaction: importance of the wash after hydrolysis

Washing in absolute ethanol after FEULGEN hydrolysis minimizes losses of DNA. The hydrolysis in HCl diluted in tetrahydrofuran is not superior in this respect to conventional hydrolysis if this is followed by an ethanol wash. These conclusions are based on cytophotometric and radiometric experiments made on salivary glands of sciarid larvae.

Pseudolycoriella hygida (Sauaia and Alves)-An Overview of a Model Organism in Genetics, with New Aspects in Morphology and Systematics

Pseudolycoriella hygida (Sauaia & Alves, 1968) is a sciarid that has been continuously cultured in the laboratory for nearly 60 years. Studies on this species have contributed to the understanding of DNA puffs, which are characteristic of Sciaridae, and to the knowledge of more general aspects of insect biology, including cell death, nucleolar organization, and the role of the hormone ecdysone during molting. The genome of Psl. hygida has now been sequenced, and it is the third publicly available sciarid genome. The aim of this work is to expand the current knowledge on Psl. hygida. The morphology of the adults is revisited. The morphology of larvae and pupae is described, together with the behavior of immature stages under laboratory conditions. Cytogenetic maps of the salivary gland polytene chromosomes are presented, together with a comparative analysis of the mitotic chromosomes of six different sciarid species. Pseudolycoriella hygida was originally described as a species of Bradysia and recently moved to Pseudolycoriella. We examine here the systematic position of Psl. hygida in the latter genus. Our results extend the characterization of an unconventional model organism and constitute an important resource for those working on the cytogenetics, ecology, taxonomy, and phylogenetic systematics of sciarids.