Differentiation of transplanted larval salivary glands of Drosophila hydei in adults of the same species

Abstract

Salivary glands implanted in adult milieu without simultaneous implantation of larval ring glands showed further development and differentiation. The development of the glands was tested by thymidine-HR and uridine-H? incorporation in the chromosomes and by proline-Hy incorporation in the cytoplasm. Differentiation was evaluated on the basis of the presence or absence of mucopolysaccharide synthesis in the cells.Chromosomal thymidine incorporation was observed to proceed for a longer period in the adult milieu. DNA measurements revealed that at least in some cells of glands which were implanted at a mid third instar stage the level of polyteny is increased to a level which is never reached during normal development.Glands implanted at a mid third instar stage showed chromosomal uridine incorporation until at least 18 days after implantation.Comparison of the chromosomal puffing patterns in normal and implanted glands revealed that the chromosomes are still able to produce specific puffs after at least three weeks of implantation.In general, glands which were implanted at younger stages of normal development showed a higher response to the adult milieu than glands implanted at a stage near to puparium formation. Also the individual cells of implanted glands showed obvious differences in their response to the adult milieu. It was concluded that the growth and differentiation of the gland cells proceeds but that the regulation and coordination of the processes are disturbed in the adult milieu.The salivary glands of Drosophila hydei synthesize and store a mucopolysaccharide in their distal cells during the third instar. This mucopolysaccharide is presumed to be the glue by which the larvae become attached to the substrate at the time of puparium formation. From a study of the cellular events which are correlated with the synthesis of this substance, it was found that the onset of synthesis is correlated with a special DNA content (level of polyteny) of the nucleus. During normal development the synthesis of the mucopolysaccharides starts during early third instar in the extreme distal cells of the gland. In the course of mid third and late third instar a successive rise in polyteny could be shown in cells which lack the mucopolysaccharide component. A certain high level of polyteny was always found in cells situated at the boundary of mucopolysaccharide containing cells. This boundary shifts during development in the direction of the glandular duct: A successive rise in DNA content is followed by a n increase in the number of cells con-J. EXP. ZOOL.., 160: 299-318.taining the glue substance. At the time of paparium formation, finally, only a small number of cells (15-30) do not contain this substance. At this moment chromosomal replication has stopped.From the work of Bodenstein ('43), it is known that salivary glands which are transplanted into adults can survive for long periods. Recently, Hadorn et al. ('63) showed that the nuclei of a number of cells continue replication when salivary glands are transp...

Replication in Drosophila chromosomes. IX. Stimulation of initiation of polytene replication cycles in vitro by juvenile hormone

“…In this context, we have also seen (data not presented) that in vitro treatment with ZR 515 fails to stimulate any new polytene replication cycle in salivary glands from older late third instar larvae. Comparable results were obtained by Berendes and Holt (1965) in their studies on transplantation of larval salivary glands into adult abdominal cavity. Thus, it seems that the stimulatory effect of JH on polytene replication cycles may also depend upon the developmental and physiological status of the target cell.…”

“…As noted in the Introduction, the peaks of polytene replication in salivary gland nuclei during intermoult periods of larval life coincide with higher titers of JH in the haemolymph. Also, when Drosophila larval salivary glands are transplanted into the adult abdominal cavity where the JH titer is high (Riddiford and Truman, 1978), they continue polytene replication cycles beyond normal levels (Berendes and Holt, 1965). Recently, a stimulatory effect of JH on DNA synthesis in ovarian follicles of Leucophaea maderae (Koeppe and Wellman, 1980) and polyploid nuclei of the fat body in locusts (Nair et al, 1981) has also been shown.…”