|其他摘要||In this sduty, conventional karyotype analysis, chromosome microdissection techniques and fluorescence in situ hybridization (FISH) had been applied to studies of cytology and molecular cytogenetics of four different plants. Firstly, a karyotype study was performed on Yunnanopilia longistaminea. Secondly, the karyotypes of four geographical populations of Whitfordiodendron filipes were studied. Thirdly, the molecular cytogenetics was studied in two species of Paris by chromosome microdissection techniques and FISH. The origin and evolution of plants were studied at different levels.
1. The karyotype study of Yunnanopilia
A karyotype study was performed on Yunnanopilia, a genus of Opiliaceae from the Red River Valley, South-Central Yunnan Plateau, China. The karyotype formula is: 2n=2x=20=6m+12sm+2st. The chromosome number of Yunnanopilia is consistent with the existing chromosome numbers of other genera of Opiliaceae. Based on the result, there was little differentiation in the karyotypes among genera of Opiliaceae. By analyzing the karyotype of Yunnanopilia, it can be concluded that the differentiation degree of Yunnanopilia is low both in relative length of homologous chromosome and arm ratio of homologous chromosome.The karyotype belongs to 3A type which is relatively symmetrical and original. The result provided evidence for reconsidering the taxology status of the Yunnanopilia longistaminea.
2. The karyotype studies of four geographical populations of Whitfordiodendron filipes
Karyotype studies were performed on four geographical populations of Whitfordiodendron filipes, a species of Whitfordiodendron Elmer (Leguminosae) from China. The chromosome numbers of four populations are all 2n=16. The karyotype formulas of four populations (Yongping, Heko, Wenshan and Simao) are 2n=16=13m+3sm, 2n=16=8m+8sm, 2n=16=7m+9sm and 2n=16=7m+9sm. The karyotypes of Yongping population and Hekou population both belong to 2A type. Karyotypes of other two populations both belong to 2B type. The four populations in this study were collected respectively from Yongping, Hekou, Wenshan and Simao, which locate the west, southwest and southeast of Yunnan province. This study revealed that the karyotype variation in the four populations of W. filipes is not apparent.
3. The FISH of two species in Paris L.
Molecular cytogenetic studies were performed on two species (Paris cronquistii and Paris polyphylla) of Paris in Trilliaceae by chromosome microdissection techniques and FISH.
Paris cronquistii was studied from three aspects. Firstly, the karyotype study of Paris croquistii was performed. Combining with existent studies, the karyotype of Paris cronquistii was reduced to fourteen cellular types. Secondly, B chromosome was microdissected from a metaphase cell of Paris cronquistii and then was amplified by PCR. Fluorescence in situ hybridization (FISH) was carried out in metaphase chromosomes of Paris cronquistii with B chromosome as the probe. Both the B chromosome and A chromosomes showed fluorescent signals. Therefore, it can be concluded that B chromosome was homologous with A chromosomes and probably originated from A chromosomes. Thirdly, we located the telomere repeated sequences in B chromosome of Paris cronquistii by FISH. Signals showed on the telomeres of both two types of B chromosome. Therefore, it can be concluded that B chromosome is similar as A chromosomes in the composement of chromosome structure.
In addition, the telomere repeated sequences were located in mitosis interphase and metaphase chromosomes of Paris polyphylla by FISH. The results showed that strong signals were found just in telomere of metaphase chromosomes but not in other areas of metaphase chromosomes. Based on the result, it can be inferred that chromosomes of Paris polyphylla were conservative in the process of evolution and chromosome structure variations (such as chromosome fusion, arm reversion, transposal, recombination and so on) rarely happened.|