Exposure of Drosophila melanogaster larvae to high temperature for short periods of time results in marked changes in the puffing patterns of salivary gland chromosomes. Temperature shock "induces" puffing at 9 specific loci; this pattern of induced puffs shows little developmental specificity and is similar in three strains of D. melanogaster (including the mutant lethal giant-larvae) and in D. simulans. Temperature shock also (i) retards the regression of some devel- opmentally specific puffs and (ii) results in the regression of all other puffs normal to development. The effect of temperature treatment is similar in vivo and after in vitro treatment of salivary glands. The in vitro response is not sensitive to cycloheximide. A similar pattern of induced puffs to that found after temperature treatment is found during recovery of larvae from anoxia, but additional puffs are "induced" after anoxia. The size and duration of activity of the induced puffs is dependent upon the magnitude of the treatment.

Patterns of Puffing Activity in the Salivary Gland Chromosomes of Drosophila V. Responses to Environmental Treatments

The large scale structure and dynamics of gene control circuits: An ensemble approach

Patterns of puffing activity during the third larval instar and the prepupal period of two different strains of D. melanogaster (Oregon and vg6) are compared. The variation in puffing activity observed is both quantitative (involving the mean size or timing of activity of individual puffs) and qualitative. The pattern of activity of 64% of the puffs is the same in the two strains, 12% show strain differences in puff size and 19% in the time of their activity. One puff (64C) is active only in one of the strains (vg6). In genetic experiments this puff segregates normally and the puff locus has been mapped genetically to a site coincident with, or at least very close to, the cytogenetic position of the puff. In heterozygotes the puff is homozygous only when the maternal and paternal homologues are synapsed. When the homologues are asynapsed only the homologue from the vg6 parent is puffed at 64C. With the exeption of some strains closely related to vg6 no other strain of D. melanogaster has been found to possess puffing activity at 64C. In vg6/In(3LR)C165 heterozygotes 64C forms a heterozygous puff even when the homologues are synapsed. In the discussion consideration is given to the various factors that control puff size.

Patterns of puffing activity in the salivary gland chromosomes of Drosophila. IV. Variability of puffing patterns.

Publisher Summary This chapter highlights some of the more important lacunae in the knowledge of polytene chromosome puffs, their physiology and biochemistry. While there can be little doubt that Beermann's hypothesis “that puffs represent active gene loci” is essentially correct and that puffs are regions of RNA synthesis, the molecular basis of puff information is still obscure. Several processes are presumably involved: (i) the recognition of specific chromosomal sites by controlling elements resulting in (ii) a change in the tertiary structure of the DNA-protein complex of the chromosome such that (iii) specific RNA synthesis can now take place, (iv) the control of the transport of the RNA from the puff site perhaps involving some change in the molecular structure of the RNA itself, (v) the cessation of RNA synthesis as the result of specific signals and (vi) the return of the DNA-protein complex to the pre-active state. The precise molecular events involved in these processes, and even, in some cases, the relative order of the events, is unknown. New techniques are continually being involved for an attack on these problems.

Function and Structure of Polytene Chromosomes During Insect Development

Heterozygotes for the dominant temperature sensitive mutant DTS-3 of Drosophila melanogaster die as third instar larvae when grown at 29° C. These larvae have grossly hypertrophied ring glands due to the growth of the prothoracic gland cells. The nuclei of the prothoracic glands possess polytene chromosomes which are as large as those of salivary gland nuclei. The banding pattern of these chromosomes is similar, if not identical, to that of salivary gland polytene chromosomes but the puffing patterns are quite different. The salivary gland chromosomes of DTS-3/+ larvae also hypertrophy and lack the normal ecdysone induced puffs. Both the prothoracic gland and salivary gland chromosomes of these mutant larvae react to ecdysone in vitro by the induction of similar puffs.

Patterns of puffing activity in the salivary gland chromosomes of Drosophila: IX. The salivary and prothoracic gland chromosomes of a dominant temperature sensitive lethal of D. melanogaster

The induction of changes in chromosomal activity in different polytene types of cell in Drosophila hydei.

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The induction of changes in chromosomal activity in different polytene types of cell in Drosophila hydei.