Genetic variations among 17 accessions of zoysiagrasses collected from natural populations in Japan were investigated by RFLP analyses of chloroplast DNA (cpDNA) and nuclear DNA. These accessions were classified into five species based on morphological characteristics: Zoysia japonica, Z. matrella, Z. tenuifolia, Z. sinica, and Z. macrostachya. On the basis of eight kinds of RFLPs in cpDNAs detected across accessions, six chloroplast genome types (types A-F) were identified. Although type-A cpDNA was shared by five accessions of japonica and four accessions of matrella, derivative cpDNAs of type A, which each arose by a mutation, were identified in one accession of japonica (type B) and in two accessions of matrella (type C). One accession of japonica which showed spikelets similar to those of shapes macrostachya, contained type-F cpDNA as did sinica and macrostachya. The two accessions of tenuifolia each showed a specific cpDNA type, i.e. types D and E. Genetic relationships among the 17 accessions were investigated by the RFLP analyses of nuclear DNA with 20 genomic and gene probes. A dendrogram constructed with genetic distances calculated from the RFLP patterns indicated four major groups among them. Six accessions of japonica comprised one group, whereas the one accession of japonica possessing the type-F cpDNA was clustered with macrostachya and sinica. Four accessions of matrella with type A cpDNA constituted another group in the dendrogram, showing a closer relationship to the japonica accessions than to the other two accessions of matrella. The remaining two accessions of matrella and tenuifolia accessions were grouped together. These data indicate that zoysiagrasses distributed in Japan harbor highly genetic variations, and that interspecific hybridization has occurred in natural populations.
To study the effect of the extra chromosomes on morphological characters both in vegetative and reproductive stages, a series of alien monosomic addition lines of Japanese bunching onion (Allium fistulosum L.) with extra chromosomes from shallot (A. cepa L. Aggregatum group) were grown in the experimental farm of Saga University, Saga, Japan. Several morphological characters of the alien monosomic addition lines were found to be specific for the respective alien chromosomes from A. cepa Aggregatum group. The most distinctive characteristics in each alien monosomic addition line were as follows; spheroidal spathe in FF+1A, bloom-less leaf blade in FF+2A, slow expansion of leaf in FF+3A, acuminate spathe in FF+4A, reddish-yellow leaf sheath in FF+5A, arch-like leaf brade in FF+6A, fast expansion of leaf in FF+7A, and intensely yellow anther in FF+8A. The results indicate that these character expressions are deeply related to alien genes on extra chromosomes from A. cepa Aggregatum group.
Inductions of dicentric chromosome bridges in root-tip cells and of micronuclei in pollen tetrads by X rays and maleic hydrazide (MH) were studied in Tradescantia clone BNL 4430, in order to compare the accuracies of these endpoints for mutagenicity testings with that of somatic pink mutations in the stamen hairs of the same clone, the most accurate endpoint established in higher plant testers. The frequency of dicentric bridges in root-tip cells increased with X-ray doses with a slope of 1.249 on a log-log graph, the slope value being unexpectedly small (much smaller than the theoretical value of 2 for two-break events). The dose-response curve on a log-log graph for MH-induced dicentric bridges had a somewhat smaller slope of 1.188, and the bridges observed were predominantly of chromatid type, reflecting the nature of MH acting at the S period of cell cycle. As for X-ray- and MH-induced micronuclei in pollen tetrads, on the other hand, the dose-response curves could not be determined, excepting that for X-ray-induced micronuclei in pollen tetrads at earlier stage. Namely, the data obtained from pollen tetrads at later stage were not consistent with X-ray and MH doses, and those from pollen tetrads at earlier stage were also inconsistent with MH doses. These results were contrary to our expectation that the frequency of micronuclei would be more reliable in pollen tetrads at later stage than in those at earlier stage at least in clone BNL 4430, a hybrid clone. The micronucleus assay in pollen tetrads was also found to be unsuited for determining the effects of MH. Therefore, the assay of somatic mutations in Tradescantia stamen hairs is concluded to be the most accurate and most reliable mutagenicity test system with a high degree of reappearance.
The structural genes for the ω-secalins of rye (Secale cereale) are located in the Sec-1 locus on the short arm of rye chromosome 1R. We applied PCR (polymerase chain reaction) to detect the Sec-1 locus in a wheat genomic background. A primer set we designed based on a published sequence of a ω-secalin gene amplified not only the ω-secalin sequence, but also a putative ω-gliadin sequence. We determined partial sequences of both PCR-amplified fragments and designed different primers for the specific amplification of the ω-secalin sequence. One of the new primer sets amplified DNA fragments only in rye and wheat lines carrying chromosome 1R or telosome 1RS; no amplification occurred in either euploid wheats or 1RS deletion lines. This PCR-based method would provide efficient screening for the Sec-1 locus in progeny of wheat lines carrying chromosome 1R.
There are three group I introns in the nuclear small subunit ribosomal RNA gene (SSU rDNA) of the ballistoconidiogenous anamorphic yeast-like fungus Tilletiopsis flava JCM 5186. The size of these sequences were 325 nt (position 516), 335 nt (position 1199) and 437 nt (position 1506), respectively. The introns at position 516 (T.flav516) and position 1199 (T.flav1199) belonged to subgroup IB3, and that of position 1506 (T.flav1506) belonged to subgroup IC1. The results of comparison with other group I introns found in SSU rDNA of eucaryotes showed that the positions 516 and 1199 were common positions to IB3 group I introns of fungi and green algae, and that positions 943, 1506 and 1512 were those to IC1 group I introns of fungi, and green and red algae. It is indicated that the insertion position of introns have close relationship with the nature of the subgroup to which they belonged. For phylogenetic analysis, we employed 9 IB3 introns, in which 7 were at position 516 and 2 were at position 1199, and 25 IC1 introns. The maximum likelihood tree based on the conserved region alignment showed that group I introns of subgroup IB3 were phylogenetically distant from those of subgroup IC1. T.flav516 (basidiomycete) constituted a subcluster with R.dacr516 (basidiomycete) and M.albo516 (ascomycete). T. flav1199 was located at the closer position of C.chlo1199 (green alga) than other IB3 introns at position 516. T.flav1506 was located at the subcluster, which was constituted by the 1506 introns found in SSU rDNA of fungi (B.yama1506, P.cari1506, and P.inou1506) and those of green algae (C.elli1506, C.mira1506, G.spir1506, and M.sacl1506) with IC1 introns at the position 1512 (D.parv1512 and C.sacc1512). The analysis of flanking regions showed that both 5' and 3' flanking sequences were well conserved in each insertion site, and indicated that the ancestors of the intron at different site had been inherited from the different origin. Therefore, the two IB3 introns found positions 516 and 1199, T.flav516 and T.flav1199, were supposed to have the independent ancestors. Our results supported the theory of the diversity of group I introns that group I introns had been transferred horizontally to the distinct insertion site, and were inherited and diverged vertically.
The genes for major ribosomal RNA were localized on chromosomes 5pter-p15, 9q64-qter, and 13q38-qter of the house musk shrew, Suncus murinus (Insectivora, Soricidae) by silver staining of mitotic metaphase and meiotic pachytene spreads and fluorescence in situ hybridization using the human 28S-RNA genes as a probe to mitotic metaphase spreads. The data presented indicate a correlation between sites of in situ hybridization and silver staining. The finding of nuclear materials in mitosis was in a good agreement with observation in meiosis: same chromosomes carried active NORs in both meiotic and mitotic cells.
We have identified a mariner-like element (MLE) in the genome of the silkworm, Bombyx mori. The cloned MLE, desiqnated as BmMLE, contained an ORF that was interrupted by insertions, stop codons, and frameshifts. The complete ORF sequence was estimated by sequencing the PCR products. The hypothetical protein coded by this ORF showed 34% homology to the Mos1 element of Drosophila mauritiana, and is phylogenetically very close to MLE of Hyalophora cecropia. BmMLE is present in 80 to 100 copies in the B. mori genome. Many BmMLEs with different lengths were identified by Southern blot analysis and LA PCR of the genomic DNA. The distribution of these BmMLEs differed in geographic races.
To test the hypothesis that the domestic dogs are derived from several different ancestral gray wolf populations, we compared the sequence of the displacement (D)-loop region of the mitochondrial DNA (mtDNA) from 24 breeds of domestic dog (34 individual dogs) and 3 subspecies of gray wolf (Canis lupus lupus, C. l. pallipes and C. l. chanco; 19 individuals). The intraspecific sequence variations within domestic dogs (0.00~3.19%) and within wolves (0.00~2.88%) were comparable to the interspecific variations between domestic dogs and wolves (0.30~3.35%). A repetitive sequence with repeat units (TACACGTA/GCG) that causes the size variation in the D-loop region was also found in both dogs and wolves. However, no nucleotide substitutions or repetitive arrays were specific for domestic dogs or for wolves. These results showed that there is a close genetic relationship between dogs and wolves. Two major clades appeared in the phylogenetic trees constructed by neighbor-joining and by the maximum parsimony method; one clade containing Chinese wolf (C. l. chanco) showed extensive variations while the other showed only slight variation. This showed that there were two major genetic components both in domestic dogs and in wolves. However, neither clades nor haplotypes specific for any dog breed were observed, whereas subspecies-specific clades were found in Asiatic wolves. These results suggested that the extant breeds of domestic dogs have maintained a large degree of mtDNA polymorphisms introduced from their ancestral wolf populations, and that extensive interbreedings had occurred among multiple matriarchal origins.
The spatial genetic structure within a population of an endangered plant, Cerastium fischerianum var. molle, was examined using spatial autocorrelation analysis. All individuals in 22 × 15 m area in a population were mapped and genotyped by three allozyme loci. Many spatial autocorrelation indices (Moran's I) were significantly larger than the expected values and their averages across three marker loci examined were positive in the short distance classes and the opposite pattern was shown in the larger distance classes, suggesting that individuals located nearly each other tend to have similar genotypes and pairs of individuals located far from each other tend to have different genotypes. Because the marker loci are considered to be neutral and the linkage disequilibria were not detected, the spatial genetic structure observed in this study seems to result from the restricted gene flow because of predominant selfing of C. fischerianum var. molle.
Chromosome breaks occur in a hexaploid wheat (Triticum aestivum), variety Chinese Spring carrying a single gametocidal chromosome, 2C, from Aegilops cylindrica. In an attempt to induce breakage in barley chromosomes, we introduced the 2C chromosome into six wheat-barley addition lines. Plants disomic for each of the barley chromosomes and monosomic for 2C were identified using C-banding and meiotic analysis. Chromosomal breakage was expected to occur in the progeny of these lines.
The chromosomal locations of randomly amplified polymorphic DNA (RAPD) markers were examined in shallot (Allium cepa L. Aggregatum group). A series of alien monosomic addition lines of Japanese bunching onion (A. fistulosum L.) with extra chromosomes (1A-8A) from A. cepa Aggregatum group was used as plant materials. Several decamer (OPERON KITs A, E, and G) and 12-mer (Wako DNA Oligomer sets A-1, C-4, F-4, and F-5) oligonucleotides were applied as random primers. The chromosomal locations of the 16 RAPD markers were determined; the RAPD marker OPE091600 was located on the chromosome 1A of A. cepa Aggregatum group, OPE03600 and OPE181400 on 2A, OPA12700 on 3A, OPA11950, OPE181500, OPG10800, WAA091800, WAF65900, and WAF83800 on 4A, OPE17500 and OPE182000 on 5A, OPG08500 on 6A, WAF812800 and WAF832200 on 7A, and WAC68500 on 8A. Consequently, the RAPD markers were assigned to all the chromosomes of A. cepa Aggregatum group.