Amplification of tropharium rDNA in the telotrophic ovariole of the bug,Dysdercus intermedins

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Abstract
In the telotrophic ovariole of the bug, Dysdercus intermedius, the highly endoploid tropharium nuclei which are functioning throughout the gonocycles were analysed with respect to rDNA amplification. The likewise polyploid follicle cell nuclei which degenerate at the end of each cycle of egg formation and diploid larval brain nuclei were used for comparison. A heavy satellite is pronounced only in the tropharium DNA. The restriction patterns after hybridization with a labelled probe of cloned rDNA indicated considerable differences in the amount of ribosomal genes present in the three types of nuclei. These results evidence a high degree of rDNA amplification in the germ-line derived tropharium nuclei, but nothing like this in the diploid or polyploid somatic cells. This is the first record of an amplification of rDNA in a telotrophic insect ovary occurring probably during early trophocyte differentiation. The developmental significance of high amounts of ribosomal genes in the long persisting tropharium nuclei is discussed.