Genetic linkage between cytological markers and the seed storage protein lociSec2[Gli-R2] andSec3[Glu-R1] in rye

In order to reach a higher accuracy concerning the cytological locations of the rye seed storage protein lociSec2[Gli-R2] andSec3[Glu-R1] located within chromosome arms 2RS and 1RL, respectively, the linkage relationships between the following loci were analyzed: isozyme lociGpi-R1,Mdh-R1, andPgd2, translocationT273W (Wageningen tester set, involving chromosome arms 1RS and 5RL), the telomere C-bands of chromosome arms 1RL (tL1), 2RS (tS2), and 5RS (tS5), and three interstitial C-bands in chromosome arm 1RS (iS1), in the middle of chromosome arm 1RL (iL1), and in the middle of chromosome arm 2RL (iL2), respectively. The data indicated that locusSec3 is located in the distal half of chromosome arm 1RL (between C-bandiL1 and locusPgd2), while locusSec2 is located a short distance (2.9 ± 1.4%) from the telomere C-band of chromosome arm 2RS.     

A cytogenetic map on the entire length of rye chromosome 1R,including one translocation breakpoint,three isozyme loci and four C-bands

Summary A cytogenetic map of the whole 1 R chromosome of rye has been made, with distances between adjacent markers shorter than 50% recombination. Included in the map are isozyme loci Gpi-R1, Mdh-R1 and Pgd2, the telomere C-bands of the short arm (ts1) and the long arm (tl1), two interstitial C-bands in the short arm proximal to the nuclear organizing region (NOR) (is1) and in the middle of the long arm (il1), respectively, and translocation T273W (Wageningen tester set). By means of electron microscope analysis of spread pachytene synaptonemal complexes, the breakpoint of this translocation was physically mapped in the short arm of 1R, proximal to NOR, and in the long arm of 5R (contrary to previous assumptions). The data indicated the marker order: ts1 — Gpi-R1 — is1 — T273W/Mdh-R1 — il1 — Pgd2 — tl1. A comparison between genetic and physical maps revealed that recombination is mainly restricted to the distal regions of both arms. For the translocation T273W, in heterozygotes no recombinants were observed between the translocation breakpoint and its two adjacently located markers (is1 and Mdh-R1), but recombination was not reduced in the distal regions of the chromosome. The segregations of several other isozyme and C-band markers also analyzed in the investigation presented here were consistent with observations of earlier authors concerning chromosome asignment and linkage relationships.     

两种突颜蝗的染色体C带核型研究

采用染色体C分带技术初次对癞蝗科Pamphagidae中国特有的突颜蝗属Eotmethis B.-Bienko 2个种,即天祝突颜蝗E. tientsuensis (Chang)和景泰突颜蝗E.jintaiensis Xi et Zheng的精原细胞有丝分裂中期和初级精母细胞减数分裂中期（中期I）染色体C带核型进行了比较研究。结果表明: 2种突颜蝗的染色体基数、着丝粒位置及染色体分组形式相同,且与前人的研究结果基本吻合,反映了癞蝗科昆虫核型的稳定性。同时,2种突颜蝗染色体相对长度值较为接近;结构异染色质总含量没有明显差异;并且两者无论在精原细胞有丝分裂中期还是减数分裂中期I细胞,其3号、4号和X染色体上都显现深着色较大块的着丝粒C带, 9号染色体上都出现大块深着色的端部C带,2号染色体上都发生清晰的近中部居间C带,以上反映了2个种在系统发生上的亲缘关系。另外,2种突颜蝗在C带带型上的差异,在1号、7号、8号染色体上有不同程度的反映,尤其是对应的7号、8号染色体上着丝粒C带块的大小和强弱有明显变化。     

Identification of the chromosomes showing neocentric activity in rye

Summary Chromosomes showing neocentric activity were identified with the aid of the C-banding technique in an inbred line of rye, 1940-129 of cv. Stålråg. The frequency of cells with neocentrics varied from 34 to 35.7% at first anaphase, and from 32 to 68% at second metaphase. In most cells only one chromosome showed the activity. It always belonged to the group 4-5-6R, and in cells where individual identification of chromosomes was possible the activity was invariably located at the telomere of the arm 4RS. When in rare cases two or three chromosomes were active, one chromosome again belonged to the group 4-5-6R, the other was identified in four cells as a member of the group 2-3-7R, but it is possible that all the telomeres with a prominent C-band can occasionally show the activity. It is assumed that certain telomeric regions remain in the active state at both meiotic divisions and offer secondary accumulation sites for kinetochoric proteins.     

Localization of viral transforming sequences within marker chromosomes associated with tumor formation and progression in a murine fibrosarcoma

The low-metastatic RSV-transformed fibrosarcoma line B77-3T3 and its metastatic variant AA12, selected in vitro, have been analysed by blot and in situ hybridization with v-src and murine c-myc specific probes in order to detect molecular rearrangements underlying the transition from the low-metastatic to the high-metastatic phenotype. Previous cytogenetic analysis had evidenced that a marker chromosome of the parental tumor line (chromosome A) is replaced in the metastatic counterpart by a new marker chromosome (chromosome B), possibly arisen by duplication of a chromosome A segment, included between two C-positive regions (L. Doneda et al., 1985). In situ hybridization on chromosome spreads of the two related lines with a ³H-labelled v-src probe showed that src sequences are located within the marker chromosomes A and B, and the percentage of grains over the AA12 marker chromosome is always double that found on the B77-3T3 marker. These signals were considered to identify v-src sequences as they were found to be slightly amplified in the metastatic variant DNA by blot hybridization with the v-src probe. As regards the intrachromosomal location of the signals, most grains were clustered near the heterochromatic bands, suggesting a possible role for heterochromatic sites in tumor formation and evolution. No involvement of the A and B marker chromosomes was shown by in situ hybridization experiments with a c-myc probe. However the dosage of c-myc sequences was also found to be slightly increased in the metastatic variant DNA.     

C-heterochromatin during synapsis and recombination in grey cockroach Nauphoeta cinerea spermatogenesis

The behavior of large, distal, C-heterochromatic blocks in the spermatogenesis of the grey cockroach Nauphoeta cinerea was investigated by light and electron microscopy. In early meiotic prophase I, heterochromatic blocks of some autosomes are involved in the nonhomologous association and form a chromocenter. Fluorescent in situ hybridization (FISH) with a ribosomal DNA (rDNA) probe revealed the signal on only two pairs of middle chromosomes not engaged in the chromocenter formation; therefore, ectopic conjugation was not caused by the formation of a nucleolus. Analysis showed that chromocentric heterochromatin does not participate (functionally or spatially) in basic meiotic events. Heterochromatin does not participate in the formation of a bouquet, initiation of homologous synapsis, or recombination events. The chromocenter disintegrates at the end of the pachytene when synapsis is totally completed. Heterochromatin polymorphism results in asymmetric synaptonemal complexes (SCs) with different degrees of synaptic adjustment. The axis of the sex univalent (male sex determination is XO) is split in various sites, regardless of heterochromatin localization.     

Chiasma distribution in rye chromosomes of diploid rye and in wheat/rye addition lines in relation to C-heterochromatin

Summary In five genetically different inbred lines of rye and in the seven Chinese Spring/Imperial wheatrye addition lines, chiasma distribution in rye chromosomes was studied with respect to the amount and position of constitutive heterochromatin (Giemsa C-bands). In all inbred lines, rye chromosomes with one primary terminal band were more frequently found as univalents than those with primary bands on both telomeres. These chromosomes were most probably 5R and/or 6R. In the addition lines a highly significant reduction in the number of arms bound by chiasmata was found for rye chromosomes 5R and 6R. Because of the similar chiasma distribution in the inbred lines and in the rye chromosomes of the addition lines, no effect of the wheat genome on the number of chiasmata in the rye chromosomes can be ascertained. However, a relationship between chiasma frequency and chromosome arm length seems to exist, since under reduced chiasma conditions the two shortest arms of the rye complement, those of chromosomes 5R and 6R, frequently fail to form a chiasma. No effect of the large blocks of constitutive heterochromatin in the telomeres of the rye chromosomes on the position of chiasmata within a bivalent could be established.This study was financially supported by the Deutsche Forschungsgemeinschaft     

Effects of constitutive heterochromatin and genotype on frequency and distribution of chiasmata in the seven individual rye bivalents

Summary Number and distribution of chiasmata were studied in the single pair of homologous rye chromosomes in 29 chromosomal F₁ hybrids between the seven disomic wheat rye addition lines of Chinese Spring/ Imperial and five selected inbred genotypes of cultivated rye by using the differential Giemsa staining technique. The results indicate that the number and position of chiasmata is independent from the amount and position of C-heterochromatin. Genotype had an effect on chiasma number, whereas chiasma distribution within bivalents appeared to be determined by morphological features of chromosomes. Late replicating DNA in constitutive heterochromatin may delay the separation of half bivalents if chiasmata are formed between them and the centromere.Supported by Deutsche Forschungsgemeinschaft, Bonn     

Genetic mapping of cytological and isozyme markers on chromosomes 1R, 3R, 4R and 6R of rye

Cytogenetic maps involving chromosomes 1R, 3R, 4R and 6R have been developed from the analysis of offspring of crosses between multiple heterozygous rye plants. The maps include isozyme loci GpiR1, Mdh-R1 and Pgd2 (located in chromosome 1R), Mdh-R2 (located in chromosome 3R), Pgm-R1 (located in chromosome 4R) and Aco-R1 (located in chromosome 6R). Various telomeric and interstitial C-bands of these four chromosomes, the centromere split of chromosome 3R, and translocation TR01 were used as cytological markers. By means of electron microscope analysis of spread pachytene synaptonemal complexes, the breakpoint of TR01 was physically mapped in chromosome arms 4RS and 6RL. From the linkage data, conclusions were derived concerning the cytological locations of the isozyme loci and the physical extent of the evolutive translocations involving chromosome arm 6RL.     

Genetic mapping between Gli-B1 locus and a telomeric C-heterochromatin band in wheat

Summary Using C-banding it has been possible to prove that the bread wheat varieties Holdfast and CapelleDesprez shows an intense band of telomeric heterochromatin on the short arm of chromosome 1B, while the variety Pané-247 presents a very thin band. Gliadin study using pH-acid electrophoresis revealed the existence of differences in the Gli-B1 locus in the three varieties. Analysis of the progeny of the (P x H) x CD hybrid revealed recombination between the heterochromatin C-band and locus Gli-B1, and allowed the genetic distance between the two markers to be calculated as 6.55±3.16 cMorgan. This is the first time the genetic distance from a locus to the chromosome telomere has been directly obtained in wheat. The heterochromatin C-band studied here gives us a cytological marker on chromosome 1B that can be used as a reference point in the localization of other genes.