Genaktivitäten in den Riesenchromosomen von Chironomus tentans und ihre Beziehungen zur Entwicklung—III : Das Aktivitätsmuster in Phasen der Entwicklungsruhe

Abstract

The puffs in giant chromosomes of Diptera are morphological sings of gene activities. The subject of this series of papers is the relationship between these gene activities and developmental processes in the larva. In this paper we present results on puff behaviour during phases of dormancy which may serve to extend our previous studies of puffing during the normal course of development and in cases of ecdysone-induced pupation. The lower metabolism of dormancy expresses itself in the salivary gland chromosomes by a reduction of puff frequency. However, any puffs which are active in rapidly growing larvae may also be present in dormant larvae. While the frequency of some puffs is strongly reduced, the frequency of others is unchanged or even increased. Thus, puffs which are present in a given stage of development must be concerned with independent metabolic processes in the cell. There is no sign that the metabolic processes in the salivary gland cells of dormant larvae are different from those in rapidly growing ones. In the pupal moult following dormancy the same sequence of gene activations occurred as in prepupae from normal cultures and after experimental induction of pupation. Some larvae fell back into a phase of dormancy after they had passed through some of the processes of the pupal moult. This was accompanied by lack of ecdysone in the haemolymph. Dormant prepupae lack all those puffs which are specific for metamorphosis. This agrees with our former conclusion that even such processes in the course of moulting which are not directly influenced by ecdysone are under the control of hormone-dependent processes.