Microsatellite-centromere distances and microsatellite diversity in different ploidy classes of Chinese shrimp (Fenneropenaeus Chinensis)

This is the first report of microsatellite-centromere mapping in this commercial species Fenneropenaeus Chinensis, and will be important for providing fixed points in the linkage groups of genetic maps. Triploid Chinese shrimp was induced by heat shock. The fertilized eggs were treated either by retention of the first polar body or the second polar body to produce Meiosis I (MI) or Meiosis II (MII) triploid. The triploidy status in each Chinese shrimp could be confirmed by nine polymorphic microsatellite loci, in which the parents with different alleles and the female parents were each heterozygous. The nine loci were mapped in relation to their centromeres in three MII triploid families, which were induced by retention of the second polar bodies after fertilization with sperm. Microsatellite-centromere (M-C) distances ranged from 9.6 cM to 37 cM under the assumption of complete interference. Information on the positions of centromeres in relation to the microsatellite loci will represent a contribution towards assembly of genetic maps in F. chinensis. Twelve polymorphic microsatellites were used to assess the heterozygosity and allelic diversity in different ploidy classes. As expected, triploids were significantly more polymorphic than diploids. The diploids had an average heterozygosity and allelic diversity value of 0.86, whereas the triploids heterozygosity averaged 0.93 and had allelic diversity value of 1.29. However, MI triploids were not significantly more polymorphic than MII in the microsatellite loci.

Defining the orientation of the tandem fusions that occurred during the evolution of Indian muntjac chromosomes by BAC mapping

The Indian muntjac (Muntiacus muntjak vaginalis) has a karyotype of 2n=6 in the female and 7 in the male, the karyotypic evolution of which through extensive tandem fusions and several centric fusions has been well-documented by recent molecular cytogenetic studies. In an attempt to define the fusion orientations of conserved chromosomal segments and the molecular mechanisms underlying the tandem fusions, we have constructed a highly redundant (more than six times of whole genome coverage) bacterial artificial chromosome (BAC) library of Indian muntjac. The BAC library contains 124,800 clones with no chromosome bias and has an average insert DNA size of 120 kb. A total of 223 clones have been mapped by fluorescent in situ hybridization onto the chromosomes of both Indian muntjac and Chinese muntjac and a high-resolution comparative map has been established. Our mapping results demonstrate that all tandem fusions that occurred during the evolution of Indian muntjac karyotype from the acrocentric 2n=70 hypothetical ancestral karyotype are centromere-telomere (head-tail) fusions.

Identification and molecular evolution of cow CENP-A gene family

The centromere protein A (CENP-A), a histone H3-like protein, provides an essential role for chromosomal segregation during mitosis and meiosis. In this study we identified ten new CENP-A-like genes (excluding the original CENP-A gene) in cow by searching

New insights into the karyotypic relationships of Chinese muntjac (Muntiacus reevesi), forest musk deer (Moschus berezovskii) and gayal (Bos frontalis)

To investigate the karyotypic relationships between Chinese muntjac (Muntiacus reevesi), forest musk deer (Moschus berezovskii) and gayal (Bos frontalis), a complete set of Chinese muntjac chromosome-specific painting probes has been assigned to G-banded chromosomes of these three species. Sixteen autosomal probes (i.e. 6-10, 12-22) of the Chinese muntjac each delineated one pair of conserved segments in the forest musk deer and gayal, respectively. The remaining six autosomal probes (1-5, and 11) each delineated two to five pairs of conserved segments. In total, the 22 autosomal painting probes of Chinese muntjac delineated 33 and 34 conserved chromosomal segments in the genomes of forest musk deer and gayal, respectively. The combined analysis of comparative chromosome painting and G-band comparison reveals that most interspecific homologous segments show a high degree of conservation in G-banding patterns. Eleven chromosome fissions and five chromosome fusions differentiate the karyotypes of Chinese muntjac and forest musk deer; twelve chromosome fissions and six fusions are required to convert the Chinese muntjac karyotype to that of gayal; one chromosome fission and one fusion separate the forest musk deer and gayal. The musk deer has retained a highly conserved karyotype that closely resembles the proposed ancestral pecoran karyotype but shares none of the rearrangements characteristic for the Cervidae and Bovidae. Our results substantiate that chromosomes 1-5 and 11 of Chinese muntjac originated through exclusive centromere-to-telomere fusions of ancestral acrocentric chromosomes. Copyright (C) 2005 S. Karger AG, Basel.

MEIOTIC CHROMOSOME BEHAVIOR IN FEMALE INTERSEXES OF ARTIFICIAL TRIPLOID TRANSPARENT-COLORED CRUCIAN CARP

Chromosome behavior in meiosis was studied by air-drying, C-banding and surface-spreading methods in female intersexes of artificial triploid transparent-colored crucian carp (Carassius auratus). Chromosome pairing and contraction were obviously asynchronous. The preferential pairing of two homologous chromosomes was the major pattern of chromosome pairing, and a few triple pairing, repeated pairing, telomer or centromere associating and multiple pairing were also observed in the pachytene cells. The metaphase I cells were mainly composed of univalents, bivalents and trivalents, as well as few of other multivalents, such as tetravalents, pentavalents, hexavalents and heptavalents, were also found in some metaphase I cells. The chromosome elements including uni-, bi-, tri- and other multivalents varied considerably among the metaphase I cells, and the associating patterns of multivalents were also diverse. Some 6 n and 12 n cells, in which premeiotic endomitosis occurred once or twice, were found at the prophase and first metaphase of meiosis, and the pairing and associating patterns were basically similar to that of the triploid cells.

ACHT操作引起黑麦(Secale cereale)染色体的畸变和重建

用ACHT处理黑麦萌动种子，对修复前后材料的观察和分析结果表明：1. ACHT操作引起染色体数目变化和染色体断裂损失。在一定 条件和范围内，不同处理引起的这种变化具有显著差异，条件越剧烈，染色体数目变化的范围和频率愈大，断片发生的数量和频率 也愈高，同时修复前后染色体数目的变化范围和频率与断片发生的数量和频率以及它们的修复频率均表现明显的相关性。2. ACHT 操作引起染色体畸变的多样性。经ACHT处理后，胚根细胞染色体有4种断裂方式，包括着丝粒断裂、次溢痕断裂、长臂断裂和短臂 断裂等，其中着丝断裂频率最高；产生6种断片类型，包括有着丝粒和端粒的、有着丝粒而无端粒的、有部分着丝粒和端粒的、有 部分着丝粒而无端粒的、只有端粒的、既无着丝粒也无端粒的断片等。3. ACHT操作引起遗传结构重建的多样性。经ACHT处理后， 对修复24-72小时材料进行核型比较(按Stebbins 和 Levan 标准)和随体分析，处理细胞在染色体数目、大小、形态、位置等方面 均发生显著变化，说明ACHT处理使这些细胞的染色体结构和染色体组型发生了深刻变化。进一步通过Giemsa C— 带分析，观察到 多种重建染色体类型，包括易位型染色体、附加型染色体、无着丝粒染色体、化染色体、增加的m染色体以及某些带型特异的染色 体等。4. RAPD 分析从分子水平上验证了ACHT能有效地引起遗传结构的改变。所用10种引物对处理和对照材料基因组DNA的扩增产 物在条带数目、条带位置及带型特征等方面均有明显差异，其中4种引物出现条带减少，6种引物出现条带增加，后者还包括一个带 位移动。这说明两种材料的基因组DNA具有明显的RAPD反应多态性差异。This paper descripes some results draw on the basis of the observation and analysis on the rye before and after repaired through treating its budding seeds by ACHT in contrast to without ACHT: 1. ACHT manipulation caused the number variation and breakage damage of rye chromosome. Within certain conditions and timits, this phenomenon caused by different treats had signifcant difference: the more the treatment condition is drastie, the more the chageable range and frequence of rye chromosomae number, and so is the produced fragments. Meanwhile, there existed striking relationship among the changeable range and frequence of rye chromosome, the produced number and frequence of fragments and repairing frequence. 2. ACHT manipulafion engendered the diversify of rye chromosomal aberration. Four breakage patterns and six sorts of fragment were observed by watching the chromosome of the rye radicle treated by ACHT, including centric breakage (occuring in the highest frequence), secondary constriction breakage, long arm breakage and short arm breakage to the former, Comprising that with both centromere and telomere, that with centromere and without telomere, that with partial centromere and with telomere, that with partfial ceetromere and without telomere, that only with telomere and that neither with centromere nor with telomere, etc. 3. ACHT manipulation engendered the diversify or rye genetic structs reconstruction. Karureotype analysis(according to Stebbins and Levan) and satellite anaeysis were carried out to rye radicle through 24-72-hour-long recoverage after ACHT manipulation, which showed remarkable change happened on the rye chromosomal number、shape、arm ration and pattern, etc. and also on the satellite number、size、shape and location etc. Those indicated that ACHT manipulation engendered violent changes to rye chromatin structure and chromosome type. Further Giemsa C-banding analysis showed many types of reconstructed chromosome, such as translocation、addition、without centromere、st and other chromosome. 4. RAPD analysis checked the validity of ACHT on changing genetic structure of rye on the level of molecular biology. The treated and recovered rye has different amplifying band pattern by using IO valid arbitary primers selected from 40 comparing with the control.

Genetic analysis of meio- and mito-gynogenetic stocks of Paralichthys olivaceus with microsatellite markers

Twenty microsatellite markers (Po1, Po13, Po33, Po35, Po42, Po48, Po56, Po89, Po91, kop6, kop7, kop8, kop12, kop15, kop18, kop21, kop22, kop23, kop26, Po-strl) were used to assess the meiogynogenetic and mitogynogenetic stocks of the left-eyed flounder, Paralichthys olivaceus, which were derived from single pair crossing. Twelve of the 20 loci utilized showed heterozygosity in the female and were mapped in relation to their centromeres in the meiogynogenetic diploid flounder. Microsatellite-centromere map distance, calculated under the assumption of complete interference, ranged from 15.8 cM for kop22 to 50 cM for Po13, Po56 and Po89. Excluding the kop22, the heterozygosities of the rest of the loci were close to 100%, suggesting the occurrence of near complete interference on the chromosome arms that carried these loci. In the mitogynogenetic diploid flounder, each individual showed exact homozygousity and the segregation profiles did not deviate from the Mendelian 1: 1 pattern. The results indicated that there was no lethal gene linked with the loci analyzed. Such high interference accounted for the high recombination rates and large map distances. The Po13 and Po56 loci, Po91 and kop18 loci, kop15 and kop21 loci are tightly linked on the same chromosome arm in pairs.

Chromosomal mapping of 5S ribosomal RNA genes in the eastern oyster, Crassostrea virginica gmelin by fluorescence in situ hybridization

Chromosomal location of the 5S ribosomal RNA gene was studied in the eastern oyster, Crassostrea virginica Gmelin. using fluorescence in situ hybridization (FISH). Metaphase chromosomes were obtained from early embryos, and the FISH probe was made by PCR (polymerase chain reaction) amplification of the 5S rRNA gene and labeled by incorporation of digoxigenin-1 1-dUTP during PCR. Hybridization was detected with fluorescein-labeled antidigoxigenin antibodies. Two pairs of FISH signals were observed on metaphase chromosomes. Karyotypic analysis showed that the 5S rRNA gene cluster is interstitially located on short arms of chromosomes 5 and 6. On chromosome 5, the 5S rRNA genes were located immediately next to the centromere, whereas on chromosome 6, they were located approximately half way between the telomere and the centromere. Chromosomes of C. virginica are difficult to identify because of their similarities in size and arm ratio, and the chromosomal location of 5S rRNA genes provides unambiguous identification of chromosomes 5 and 6. Previous studies have mapped the major rRNA gene cluster (18S-5.8S-28S) to chromosome 2. and this study shows that the 5S rRNA gene cluster is not linked to the major rRNA genes and duplicated during evolution.

Chromosomal mapping of major ribosomal rRNA genes in the hard clam (Mercenaria mercenaria) using fluorescence in situ hybridization

Karyotype and chromosomal location of the major ribosomal RNA genes were studied in the hard clam (Mercenaria mercenaria Linnaeus) using fluorescence in situ hybridization (FISH). Metaphase chromosomes were obtained from early embryos. Internal transcribed spacers (ITS) between major RNA genes were amplified and used as FISH probes. The probes were labeled with digoxigenin-11-dUTP by polymerase chain reaction and detected with fluorescein-labeled anti-digoxigenin antibodies. FISH with the ITS probes produced two to four signals per nucleus or metaphase. M. mercenaria had a haploid number of 19 chromosomes with a karyotype of seven metacentric, four metacentric or submetacentric, seven submetacentric, and one submetacentric or subtelocentric chromosomes (7M + 4M/SM + 7SM + 1SM/ST). Two ITS loci were observed: one located near the centromere on the long arm of Chromosome 10 and the other at the telomere of the short arm of Chromosome 12. FISH signals on Chromosome 10 are strong and consistent, while signals on Chromosome 12 are variable. This study provides the first karyotype and chromosomal assignment of the major RNA genes in M. mercenaria. Similar studies in a wide range of species are needed to understand the role of chromosomal changes in bivalve evolution.