Localization of rRNA genes in the nuclear space of Calliphora erythrocephala Mg. nurse cells during polytenization

Analysis of cytomixis in tobacco microsporocytes with confocal laser scanning microscopy

Confocal laser scanning microscopy for the first time is used to examine the structure of the tobacco microsporocytes involved in the intercellular migration of nuclei (cytomixis). As is observed, the cytomictic channels are distributed over the surface of tobacco microsporocytes in a non-random manner and their number depends on the meiotic stage. Analysis of non-squash cells demonstrates the differences in cytological patterns of cytomixis in a normal meiosis of control tobacco plants (SR1 line) and the abnormal meiosis of polyploids. As a rule, two to three adjacent cells are involved in cytomixis during meiosis of control tobacco plants; after cytomixis, several micronuclei are formed in recipient cells; cytoplasts (enucleated cells) are rare; and polyads are undetectable. In the meiosis of polyploids, cytomixis is massive, with a larger number of cells (sometimes, over ten) involved in nuclear migration simultaneously; recipient cells on completion of cytomixis develop tens of micronuclei; cytoplasts and polyads are frequently detectable.

Tissue-specific differences in the spatial interposition of X-chromosome and 3R chromosome regions in the malaria mosquito Anopheles messeae Fall

Spatial organization of a chromosome in a nucleus is very important in biology but many aspects of it are still generally unresolved. We focused on tissue-specific features of chromosome architecture in closely related malaria mosquitoes, which have essential inter-specific differences in polytene chromosome attachments in nurse cells. We showed that the region responsible for X-chromosome attachment interacts with nuclear lamina stronger in nurse cells, then in salivary glands cells in Anopheles messeae Fall. The inter-tissue differences were demonstrated more convincingly in an experiment of two distinct chromosomes interposition in the nucleus space of cells from four tissues. Microdissected DNA-probes from nurse cells X-chromosome (2BC) and 3R chromosomes (32D) attachment regions were hybridized with intact nuclei of nurse cells, salivary gland cells, follicle epithelium cells and imaginal disсs cells in 3D-FISH experiments. We showed that only salivary gland cells and follicle epithelium cells have no statistical differences in the interposition of 2BC and 32D. Generally, the X-chromosome and 3R chromosome are located closer to each other in cells of the somatic system in comparison with nurse cells on average. The imaginal disсs cell nuclei have an intermediate arrangement of chromosome interposition, similar to other somatic cells and nurse cells. In spite of species-specific chromosome attachments there are no differences in interposition of nurse cells chromosomes in An. messeae and An. atroparvus Thiel. Nurse cells have an unusual chromosome arrangement without a chromocenter, which could be due to the special mission of generative system cells in ontogenesis and evolution.