Achiasmate Segregation of a B Chromosome from the X Chromosome in Two Species of Psyllids (Psylloidea, Homoptera)

The segregation of a B chromosome from the X chromosome was studied in male meiosis in two psyllid species, Rhinocola aceris (L.) and Psylla foersteri (Flor.) (Psylloidea, Homoptera). The frequency of segregation was determined from cells at metaphase II. In R. aceris, the B chromosome was mitotically stable and segregated quite regularly from the X chromosome in four geographically distant populations, while it showed less regular, but preferential segregation in one population. This was attributed to the presence of B chromosome variants that differ in their ability to interact with the X chromosome in segregation. In P. foersteri, the B chromosome was mitotically unstable and segregated preferentially from the X chromosome in spermatocyte cysts, which displayed one B chromosome in every cell. Behaviour of the B chromosome and X chromosome univalents during meiotic prophase and at metaphase I in R. aceris, and during anaphase I in P. foersteri suggested that the regular segregation resulted from the incorporation of B chromosomes in achiasmate segregation mechanisms with the X chromosome in the place occupied by the Y chromosome in species with XY system. The regular segregation of a B chromosome from the X chromosome may obscure the distinction of a B chromosome and an achiasmate Y chromosome in some cases. This revised version was published online in August 2006 with corrections to the Cover Date.     

Comparative cytogenetic studies in Sus verrucosus,Sus celebensis and Sus scrofa vittatus (Suidae,Mammalia)

Chromosome studies on the Javan warty pig (Sus verrucosus), the Sulawesi warty pig (S. celebensis) and a subspecies of the wild boar, S. scrofa vittatus, have revealed diploid chromosome numbers of 38. The morphology and C-band size of chromosome 10 are different in S. verrucosus and the two other species. Both S. verrucosus and S. celebensis have a Y chromosome that is larger than the Y chromosome of domestic and wild S. scrofa, and is submetacentric rather than metacentric. There are differences between all three species in the G-banding pattern of the long arm of the Y chromosome. The presence of 2n=38 chromosomes in the Javan warty pig and the Sulawesi warty pig provides new strong evidence that the basic chromosome number in the genus Sus is 38. The differences in karyotype between these pigs (chromosome 10 and the Y chromosome) confirm that they are separate species.     

Intraspecific chromosome variation in Cebus apella (cebidae,platyrrhini): The chromosomes of the yellow breasted capuchin Cebus apella xanthosternos wied, 1820

Chromosome studies in six wild-caught specimens of Cebus apella xanthosternos showed a distinctive chromosome pair number 11 that made it possible to distinguish this subspecies from other Cebus apella. The characteristic chromosome pair had intercalar heterochromatin unlike the “standard” chromosome type of Cebus apella and other species of the same genus, in which this chromosome pair shows a large, terminal, heterochromatic block. A comparison at the chromosomal level between different Cebus apella populations suggests that chromosome 11 in Cebus apella xanthosternos is a derived chromosome that has probably become fixed in this subspecies, either by selection or by drift in a small isolated population.     

The role of chromosomal rearrangements in the evolution of <Emphasis Type="Italic">Silene latifolia</Emphasis> sex chromosomes

Silene latifolia is a model plant for studies of the early steps of sex chromosome evolution. In comparison to mammalian sex chromosomes that evolved 300 mya, sex chromosomes of S. latifolia appeared approximately 20 mya. Here, we combine results from physical mapping of sex-linked genes using polymerase chain reaction on microdissected arms of the S. latifolia X chromosome, and fluorescence in situ hybridization analysis of a new cytogenetic marker, Silene tandem repeat accumulated on the Y chromosome. The data are interpreted in the light of current genetic linkage maps of the X chromosome and a physical map of the Y chromosome. Our results identify the position of the centromere relative to the mapped genes on the X chromosome. We suggest that the evolution of the S. latifolia Y chromosome has been accompanied by at least one paracentric and one pericentric inversion. These results indicate that large chromosomal rearrangements have played an important role in Y chromosome evolution in S. latifolia and that chromosomal rearrangements are an integral part of sex chromosome evolution.     

The eects of a ring chromosome on the meiotic segregation of other chromosomes in Saccharomyces cerevisiae

Meiotic chromosome segregation must occur with high fidelity in order to prevent the generation of aneuploid cells. We have previously described the identification and genetic characterization of a yeast mutant with defects in meiotic sister-chromatid segregation. We attributed the phenotype in this mutant to a dominant allele, which we referred to as SID1-1. These mutants appeared to exhibit high levels of nondisjunction and precocious separation of sister-chromatids of chromosome III, as well as precocious separation of sister chromatids of chromosome VIII and a univalent artificial chromosome. We show here that the unusual meiotic behavior of chromosome III in these strains is due to the presence of a ring III chromosome, rather than a mutant gene. Additional experiments demonstrate that a ring III/rod III pair alters the meiotic segregation of a univalent artificial chromosome.     

半蒴苣苔属植物染色体制片优化及染色体数目和倍性研究

染色体数目和倍性是系统与进化生物学和遗传学研究中十分重要的基础信息。为探索半蒴苣苔属染色体制片的适宜条件以及染色体数目的进化模式及其与物种的进化关系，该研究基于半蒴苣苔属染色体数目的进化历史，并根据该属植物具有叶片扦插繁殖的特性，采用叶片水培生根法获取半蒴苣苔(Hemiboea subcapitata)、弄岗半蒴苣苔(H.longgangensis)、龙州半蒴苣苔(H.longzhouensis)、江西半蒴苣苔(H.subacaulis var.jiangxiensis)、华南半蒴苣苔(H.follicularis)和永福半蒴苣苔(H.yongfuensis)6种植物的根尖材料，分析不同实验条件对染色体制片效果的影响，对染色体制片实验的条件进行优化及染色体计数，结果表明：(1)9:30—10:00取材，解离10 min以及染色15 min为半蒴苣苔属染色体制片的适宜条件。(2)上述6种半蒴苣苔属植物均为二倍体，染色体数目均为32(2n=2x=32)。(3)除个别物种染色体数目有变化以外，该属大部分物种染色体数目可能为2n=2x=32且染色体数目变化可能是非整倍化的作用，与物种进化没有明...     

Molecular and cytological characterization of an extra acrocentric chromosome that restores male fertility of wheat in the msH1 CMS system

A new CMS system designated as ‘msH1’ has been reported in bread wheat using the cytoplasm of H. chilense. While testing this system in different wheat backgrounds, a highly fertile line with chromosome number 42 plus an extra acrocentric chromosome was obtained. The extra chromosome did not pair with any wheat chromosome at meiosis, and progeny from this line which lack the acrocentric chromosome showed pollen abortion and male sterility. In order to establish the origin of this chromosome, FISH using H. chilense genomic DNA as probe was used and showed that it had originated from H. chilense chromosome(s). The novel chromosome did not possess sequences similar to wheat rDNA; however, the probe pSc119.2 from S. cereale containing the 120 bp family was found to occur at the end of its long arm. Data obtained from FISH and EST molecular markers confirm that the long arm of the acrocentric chromosome is indeed, the short arm of chromosome 1H^ch from H. chilense. We suggest that the novel chromosome originated from a deletion of the distal part of the long arm of chromosome 1H^ch. Neither the 1H^chS short arm, nor the whole chromosome 1H^ch restores pollen fertility of the alloplasmic wheat. Therefore, the restorer gene on the acrocentric chromosome must be located on the retained segment from the hypothetical 1H^chL, while some pollen fertility inhibitor could be present on the deleted 1H^chL distal segment. Disomic addition of the acrocentric chromosome was obtained and this line resulted fully stable and fertile.     

Biochemical evidence of homoeology between Triticum aestivum and Agropyron intermedium chromosomes

Summary The alcohol dehydrogenase (ADH), phosphoglucose mutase (PGM), glucosephosphate isomerase (GPI), glutamic oxaloacetic transaminase (GOT), malate dehydrogenase (MDH), leaf esterases (ESTL), leaf acid (ACPH) and endosperm alkaline (PHE) phosphatases, leaf peroxidases (PERL) zymogram phenotypes of Triticum aestivum, Agropyron intermedium, Triticum aestivum — Agropyron intermedium octoploids and six Agropyron intermedium chromosome additions to Triticum aestivum and two ditelocentric addition lines were determined. It was found that the six disomic chromosome addition lines and one ditelocentric chromosome addition line could be distinguished from one another and from the other possible lines on the basis of the zymogram phenotypes of these isozymes. The structural gene Acph-X1 was located on Agropyron chromosome L1, the genes Got-X3 and Mdh-X2 on chromosome L2, the gene Gpi-X1 on chromosome L3, the genes Adh-X1, Pgm-X1 and Phe-3 on chromosome L4, gene Perl-1 on chromosome L5 and the gene Estl-2 on chromosome L7 and chromosome arm L7d2. These gene locations provide evidence of homoeology between Agropyron chromosomes L1, L2, L3, L4, L5 and L7 and the Triticum aestivum chromosomes of homoeologous groups 7, 3, 1, 4, 2 and 6, respectively.     

Location of genes coding isozyme markers on Aegilops umbellulata chromosomes adds data on homoeology among Triticeae chromosomes

Summary Zymogram analysis was used to identify the Aegilops umbellulata chromosomes that carry the structural genes for particular isozymes. Wheat, Aegilops and wheat-Aegilops hybrid derivative lines (which contained identified Aegilops chromosomes) were tested by gel electrophoresis for isozymes of particular enzymes. It was found that Aegilops chromosome A (nomenclature according to G. Kimber 1967) carries a structural gene for 6-phosphogluconate dehydrogenase, Aegilops chromosome B carries structural genes for glucose phosphate isomerase and phosphoglucose mutase, Aegilops chromosome D carries genes for leaf peroxidases, Aegilops chromosome E carries structural genes for endosperm peroxidases, acid phosphatases and leaf esterases, Aegilops chromosome F carries a gene for embryo plus scutellum peroxidases and Aegilops chromosome G carries structural genes for endosperm alkaline phosphatases, leaf alkaline phosphatases and leaf esterases. The results obtained indicate that chromosome B is partially homoeologous of the wheat chromosomes of group 1 and 4, and chromosome E is partially homoeologous of wheat chromosomes of groups 7 and 4. Circumstantial evidence is also provided about the possible association between chromosomes C, D and A of A. umbellulata respectively with chromosomes 5, 2 and 1 of wheat.     

The female-killing chromosome of the silkworm, Bombyx mori, was generated by translocation between the Z and W chromosomes

Bombyx mori is a female-heterogametic organism (female, ZW; male, ZZ) that appears to have a putative feminizing gene (Fem) on the W chromosome. The paternally transmitted mutant W chromosome, Df(p ^Sa + ^p W + ^od )Fem, derived from the translocation-carrying W chromosome (p ^Sa + ^p W + ^od ), is inert as femaleness determinant. Moreover, this Df(p ^Sa + ^p W + ^od )Fem chromosome has been thought to have a female-killing factor because no female larvae having the Df(p ^Sa + ^p W + ^od )Fem chromosome are produced. Initially, to investigate whether the Df(p ^Sa + ^p W + ^od )Fem chromosome contains any region of the W chromosome or not, we analyzed the presence or absence of 12 W-specific RAPD markers. The Df(p ^Sa + ^p W + ^od )Fem chromosome contained 3 of 12 W-specific RAPD markers. These results strongly indicate that the Df(p ^Sa + ^p W + ^od )Fem chromosome contains the region of the W chromosome. Moreover, by using phenotypic and molecular markers, we confirmed that the Df(p ^Sa + ^p W + ^od )Fem chromosome is connected with a partially deleted Z chromosome and that this fused chromosome behaves as a Z chromosome during male meiosis. Furthermore, we demonstrated that the ZZW-type triploid female having the Df(p ^Sa + ^p W + ^od )Fem chromosome is viable. Therefore, we concluded that the Df(p ^Sa + ^p W + ^od )Fem chromosome does not have a female-killing factor but that partial deletion of the Z chromosome causes the death of the ZW-type diploid female having the Df(p ^Sa + ^p W + ^od )Fem chromosome. Additionally, our results of detailed genetic analyses strongly indicate that the female-killing chromosome composed of the Df(p ^Sa + ^p W + ^od )Fem chromosome and deleted Z chromosome was generated by translocation between the Z chromosome and the translocation-carrying W chromosome, p ^Sa + ^p W + ^od .     

Karyological observations on Turbellaria Proseriata: karyometric analysis ofMonocelis fusca,M. lineata (Monocelididae) andParotoplana macrostyla (Otoplanidae)

A karyometric analysis of the chromosome set of the marine turbellariansMonocelis fusca, M. lineata andParotoplana macrostyla has been carried out. The karyotype of the twoMonocelis species investigated (2n=6) is formed by three pairs of small and similarly sized chromosomes: InM. fusca, chromosome 1 is metacentric, chromosome 2 acrocentric and chromosome 3 is subtelocentric.M. lineata also presents one pair of metacentric chromosomes (chromosome 2), while chromosomes 1 and 3 are submetacentric.P. macrostyla (2n=12) reveals two pairs of large metacentric and four pairs of small chromosomes, three of which are metacentric, whereas the last is subtelocentric.     

“x” is not a bias,but a number with real biological significance

Recent literature criticized the use of the symbol “x” to denote basic chromosome number in cytotaxonomy. I show here that this criticism is superfluous and is based on historical confusion between the concepts of basic chromosome number (or monoploid chromosome number), which is objective, and ancestral basic chromosome number, which is always inferred, by means of several – more or less reliable – methods. The most relevant literature is discussed and, in the end, I propose the use of x for basic chromosome number and p for (hypothetical) ancestral basic chromosome number.     

Polytene chromosome maps in four species of tsetse flies Glossina austeni, G. pallidipes, G. morsitans morsitans and G. m. submorsitans (Diptera: Glossinidae): a comparative analysis

Photographic polytene chromosome maps from pupal trichogen cells of four tsetse species, Glossina austeni, G. pallidipes, G. morsitans morsitans and G. m. submorsitans were constructed and compared. The homology of chromosomal elements between the species was achieved by comparing banding patterns. The telomeric and subtelomeric chromosome regions were found to be identical in all species. The pericentromeric regions were found to be similar in the X chromosome and the left arm of L1 chromosome (L1L) but different in L2 chromosome and the right arm of L1 chromosome (L1R). The L2 chromosome differs by a pericentric inversion that is fixed in the three species, G. pallidipes, G. morsitans morsitans and G. m. submorsitans. Moreover, the two morsitans subspecies appeared to be homosequential and differ only by two paracentric inversions on XL and L2L arm. Although a degree of similarity was observed across the homologous chromosomes in the four species, the relative position of specific chromosome regions was different due to chromosome inversions established during their phylogeny. However, there are regions that show no apparent homology between the species, an observation that may be attributed to the considerable intra—chromosomal rearrangements that have occurred following the species divergence. The results of this comparative analysis support the current phylogenetic relationships of the genus Glossina.     

Genetics and mapping of new isozyme loci in Vicia faba L using trisomics

Polymorphism in ten enzyme systems (ACO, ACP, AAT, EST, FK, ME, NAG, PRX, 6PGD, and SOD) in Vicia faba L. was analyzed, revealing 13 loci, six of which have not been reported before. Inheritance, genetics, possible location, and linkage analysis were studied in 13 different F² populations trisomic for four of the six chromosomes (nos. 3, 4, 5, and 6) of the species. Each of these loci exhibited typical Mendelian inheritance except for those involved in the trisomic chromosome. Five loci have been assigned to a specific chromosome: Est-2 to chromosome 3, Fk-2 to chromosome 4, Prx-1 to chromosome 5, and Sod-1 and Pgd-p to chromosome 6. Nag-1 and Pgd-c displayed a linkage of 22.8 cM indicating a clear homology with chromosome 5 of garden pea on which both markers are syntenic.     

Karyotype analysis in some species of Consolida (Ranunculaceae) from Iran

Consolida (dc .) S. F. Gray belongs to Ranunculaceae. The genus includes about 52 species worldwide. Here we report the diploid chromosome number and chromosome size and morphology for six Consolida species. For C. anthoroidea, C. leptocarpa, C. paradoxa and C. rugulosa the diploid chromosome number is reported for the first time. All investigated species have a diploid chromosome number of 2n = 2x = 16, except for C. persica having 2n = 2x = 14. The karyotypes of all six taxa are asymmetric, consisting of all four major chromosome types: metacentric, submetacentric, subtelocentric and telocentric chromosome type. However, considering the karyotype formula, all six species could be distinguished. In all taxa, metacentric chromosome pair 1 possesses a satellite. The only exception is C. rugulosa having an additional satellite positioned on metacentric chromosome pair 2. Karyotype data allow the separation of Aconitella from Consolida. Karyotype data plus morphological evidence support the reduction of C. paradoxa to formae level of C. rugulosa. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

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.     

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.     

Trans-inactivation: Repression in a wrong place

Trans-inactivation is the repression of genes on a normal chromosome under the influence of a rearranged homologous chromosome demonstrating the position effect variegation (PEV). This phenomenon was studied in detail on the example of brown^Dominant allele causing the repression of wild-type brown gene on the opposite chromosome. We have investigated another trans-inactivation-inducing chromosome rearrangement, In(2)A4 inversion. In both cases, brown^Dominant and In(2)A4, the repression seems to be the result of dragging of the euchromatic region of the normal chromosome into the heterochromatic environment. It was found that cis-inactivation (classical PEV) and trans-inactivation show different patterns of distribution along the chromosome and respond differently to PEV modifying genes. It appears that the causative mechanism of trans-inactivation is de novo heterochromatin assembly on euchromatic sequences dragged into the heterochromatic nuclear compartment. Trans-inactivation turns out to be the result of a combination of heterochromatin-induced position effect and the somatic interphase chromosome pairing that is widespread in Diptera.     

Single‐copy gene‐based chromosome painting in cucumber and its application for chromosome rearrangement analysis in Cucumis

Chromosome painting based on fluorescence in situ hybridization (FISH) has played an important role in chromosome identification and research into chromosome rearrangements, diagnosis of chromosome abnormalities and evolution in human and animal species. However, it has not been applied widely in plants due to the large amounts of dispersed repetitive sequences in chromosomes. In the present work, a chromosome painting method for single‐copy gene pools in Cucumis sativus was successfully developed. Gene probes with sizes above 2 kb were detected consistently. A cucumber karyotype was constructed based on FISH using a cocktail containing chromosome‐specific gene probes. This single‐copy gene‐based chromosome painting (ScgCP) technique was performed by PCR amplification, purification, pooling, labeling and hybridization onto chromosome spreads. Gene pools containing sequential genes with an interval less than 300 kb yielded painting patterns on pachytene chromosomes. Seven gene pools corresponding to individual chromosomes unambiguously painted each chromosome pair of C. sativus. Three mis‐aligned regions on chromosome 4 were identified by the painting patterns. A probe pool comprising 133 genes covering the 8 Mb distal end of chromosome 4 was used to evaluate the potential utility of the ScgCP technique for chromosome rearrangement research through cross‐species FISH in the Cucumis genus. Distinct painting patterns of this region were observed in C. sativus, C. melo and C. metuliferus species. A comparative chromosome map of this region was constructed between cucumber and melon. With increasing sequence resources, this ScgCP technique may be applied on any other sequenced species for chromosome painting research.     

Negative effect of chromosome 1A on dough strength shown by modification of 1D addition in durum wheat (<Emphasis Type="Italic">Triticum durum</Emphasis>)

A monosomic addition line of Aegilops tauschii chromosome 1D in Triticum durum cv. PBW114 was produced in 1990. This line was self-pollinated and maintained for several generations while following the presence of chromosome 1D carrying the gene for red glume color. Cytological analysis indicated that two of the three derivative lines had substitution of chromosome 1D for 1A and another had substitution of chromosome 1D for 1B. One of these lines carried a pair of small chromosomes in addition to the 1D chromosome. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of the derived lines showed the presence of high-molecular-weight (HMW) glutenin encoded by the Glu-D1 locus. The small chromosome found in one of the lines had nearly regular pairing and transmission to daughter nuclei. Fluorescent in situ hybridization (FISH) and analysis of molecular markers indicated that the small chromosome was derived from the short arm of chromosome 1A and carried the Glu-A3 locus. Microsatellite mapping based on the deletion bin map revealed that the small chromosome had terminal deletions on both the terminal and centromeric sides. The line with the small chromosome showed improvement of the sodium dodecyl sulfate (SDS)-sedimentation value as compared to parent durum. However, the increase in SDS-sedimentation value was more significant in the substitution line of chromosome 1D for 1A without the small chromosome. These facts suggest a negative effect of the Glu-A3 locus on dough strength. The sequence of the Glu-D1 locus from these lines showed that the HMW glutenin subunits were Ae. tauschii specific 2^t + T2, which were previously found to be associated with poor rheological properties and bread loaf volume in synthetic hexaploid wheat by other workers. Thus, the significant improvement in the SDS-sedimentation value of the substitution line of 1D for 1A suggests that the absence of the negative effect of chromosome 1A on quality is more important than the presence of Glu-D1 of Ae. tauschii.