Analyses Of Location Of Telomere DNA And RDNA In Several Species In Gramineae By Fluorescence In Situ Hybridization

Maize belongs to genus Zea of tribe Maydeae in Gramineae. Genera Tripsacum and Coix are the close relatives of the genus Zea in the tribe Maydeae. Homologous degree of repetitive DNA sequences among different species reveals their evolutionary relationship in a certain degree. It is a simple approach for identifying distribution of the repeated sequences on chromosomes.1. Quantitative chromosome mapping is a new developed molecular cytogenetic technique in recent years. It is undertaken by quantitatively analyzing the intensely and faintly stained regions or bands on chromosomes using computer software. Accuracy of chromosomal identification could be notably improved by the quantitative analysis. Mitotic metaphase chromosomes of Pennsetum purpureum Schumach studied cytologically have been proved to be hardly distinguishable due to their morphological similarity and the lack of distinct chromosomal landmarks. The metaphase chromosomes, of Pennsetum purpureum Schumach showed obvious differences among intense and faint regions stained by DAPI. The intensely and faintly stained regions corresponded to more condensed and more dispersed chromatin fibers along chromosomes, respectively. The uneven stained regions can be used as key markers to characterize chromosomes of Pennsetum purpureum Schumach and facilitate identification of homologous chromosomes. Distributional DAPI stained patterns along each chromosome were quantified by MetaMorph software. Based on the data besides chromosomal relative length and arm ratio, the quantitative chromosome map was constructed. The chromosome map could illustrate not only the more distinctive chromosome features, but also fractional length of differential condensation regions. The quantitative chromosome map could provide essential information for chromosomal identification.2. Like other special repeat sequence, for example, telomere DNA, its distribution had been analysesed in different mitotic phase in maize and barley by FISH and Fiber-FISH. there was bne pair of signals on each chromosome, but it had shown clearly that some signals were strong, some were weak in different chromosomes. In order to further study, with a new method of preparation of DNA fibers which has conquered the disadvantage of the way of squashing in liquefacient nitrogen,high-quality fibers were been gotten from maize (Zea mays) which has large genome and contains numerous types of highly repeat DNA elements. The result detected the copies of the telomere DNA on the maize chromosomes with the Fiber-FISH and showed the clear variability among different chromosomes. In this study, the variability of number of telomere DNA in maize genome was discussed, we have located and analyzed the sites of the 45 S and 5S rDNA on the mitotic metaphase chromosomes of barley (Hordeum vulgare L.). The results indicated that there were two pairs of signs detected for 45S rDNA, each at IS and 2L. The signal of 5S rDNA was relatively weak, and it was located on 3L. The copy number of 5S rDNA was determined by extended DNA fiber based on DNA fiber fluorescence in situ hybridization (Fiber-FISH) in barley genome. It could be estimated that the copy number was about 408-416 for 5S rDNA. In this study, the variability of number of rDNA in genome among different barley species was discussed.3. Pennsetum purpureum Schumach is a good grazing. Up to now, little cytological studies in this species have been carried out. In this study, a classic karyotype of Pennsetum purpureum Schumach was constructed according to chromosome length, centromere position, and the occurrence of NOR, and then an kamogram on the basis of the 4'-6-diamino-2-phenylindole dihydrochloride staining pattern of mitotic metaphase chromosomes was developed to depict the distribution of heterochromatin in the Pennsetum purpureum Schumach genome and in some extend it can reflect the DNA content of the chromosome. FluoresceceT in hybridization (FISH) was performed to determine genomic distribution of rDNA in Pennsetum purpureum Schumach. It was found that there were two pairs of signals of 45S rDNA located on different chromosomes, and one pair of 5S rDNA signals was mapped on the long arms of chromosome 7. The karyotype will be useful for evolutional, structural and functional genomic studies in Pennsetum purpureum Schumach. We also discuss the relationship between the site numbers of rDNA and genome ploidy of Pennsetum purpureum Schumach.4. there were wide syntenity and colinearity among the gramineous plants.Ahn and Tankley found that rice and maize had colinearity when they made a map in maize genome with rice cDNA. In Dunford et al study it indicated further that conservation of DNA marked sequence in delicated filed (< 1.6cM or 1Mb) rice and the species like barley. The study of location of corresponding linkage group in maize, wheat, cane, and sorghum had established the chromosome map in gramineous original ancestor plants eventually. In our study, with the result of FISH in maize and barley genome and the signals of rDNA location, some things about analysis and comparison could been done of conversation and variation of sequence in different defined locations between the chromosomes of maize and barley, according to the speciality of conversation of different sequence in different genome, and the relationship between maize and barley in evolution had been discussed. Far from the grass species, it would be more veracious to use some research in one species to the other, like the location of genes and etc, and it would benefit the study of genetic breediiig in some important gramineous plants and the exploration of the clues of their evolution.