The International Journal of Developmental Biology

Int. J. Dev. Biol. 52: 179 - 185 (2008)

Vol 52, Issue 2-3

Special Issue: Developmental Biology in Poland

Accessory nuclei in insect oogenesis: in search of the function of enigmatic organelles

Published: 30 November -0001

Mariusz K. Jaglarz, Malgorzata Kloc1 and Szczepan M. Bilinski*

Institute of Zoology, Jagiellonian University, Krakow, Poland and 1Department of Biochemistry and Molecular Biology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas, USA


This review compiles present knowledge of the structure and molecular composition of the enigmatic cytoplasmic organelles called accessory nuclei. Most typically, they are found in the perinuclear cytoplasm in oocytes of insects and several other invertebrates. Accessory nuclei originate by budding of the oocyte nucleus (germinal vesicle) and are surrounded by an enelope identical to the nuclear envelope. They contain one or several dense inclusions called pseudonucleoli immersed in a translucent ground substance or matrix. Comparative analysis of the morphology, molecular composition and the ultimate fate of accessory nuclei and their inclusions revealed that there are two basic types of these organelles in insect oocytes. In mallophagans, accessory nuclei are associated with the oocyte nucleus throughout entire oogenesis and at least some of them are connected to the germinal vesicle by slender stems. Each accessory nucleus contains a single, dense, RNA-positive inclusion which is likely to correspond to a nucleolus. In hymenopterans, accessory nuclei initially surround the germinal vesicle but during oogenesis they separate from it and migrate toward the peripheral ooplasm. Within the accessory nucleus matrix usually two distinct inclusions develop. One of these is perfectly spherical, contains coilin and small nuclear ribonucleoproteins and is homologous to the Cajal body. In the light of recent discoveries, we discuss the role accessory nuclei play in insect oogenesis and early embryogenesis.


accessory nuclei, oogenesis, organelle distribution, snRNP, Cajal body

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