Population differences in the expression of nucleolus organizer regions in the grasshopperEyprepocnemis plorans

Summary Fluorescence in situ hybridization revealed the presence of ribosomal RNA genes in paracentromeric regions of all A chromosomes and in the distal half of B chromosomes in embryonic cells from Moroccan specimens of the grasshopperEyprepocnemis plorans. The expression of these genes was monitored by the presence of nucleoli attached to each chromosome bivalent in diplotene cells from males collected from two different Moroccan populations and was compared to previous data of Spanish populations. Whereas only the nucleolus organizer regions (NORs) on S₉–S₁₁ and X chromosomes were active in the Spanish specimens. Moroccan individuals showed NOR activity in all chromosomes. The rRNA genes on the B chromosome were inactive in both populations. The S₉ and S₁₀ NORs were less active in Moroccan specimens than in Spanish specimen, which might be partly explained by the negative interdependence for expression of the S₁₀ NOR with respect to those on L₂ and X chromosomes. On the other hand, the X NOR was more active in Moroccan specimens than in Spanish specimens, and this might be partly due to the positive effect that the presence of B chromosomes has on the expression of this NOR. The implications of these observations on current models of NOR activity regulation are discussed.Abbreviation NOR nucleolus organizer region     

Cytochemical immunolocalization of the abundant pistil protein Sk2 in potato (Solanum tuberosum)

S_k2 protein is the most abundant member of the pistil-specific proteins of Solanum tuberosum. S_k2 protein has been localized by use of a polyclonal antibody (anti-S_k2) in the pistils of four clones of Solanum tuberosum. In the stigmas S_k2 protein accumulates to a high level in the cytoplasm of the internal secretory cells underlying the papillae one day prior to anthesis. In styles, the intercellular matrix of the transmitting tissue cells is intensely labelled by anti-S_k2. S_k2 protein is present in all four clones and shows the same labelling pattern. The possible role of the S_k2 protein in pollen tube growth is discussed.     

Expression of a bacterial effector,harpin N,causes increased resistance to fire blight in <Emphasis Type="Italic">Pyrus communis</Emphasis>

The rapid and effective activation of disease resistance responses is essential for plant defense against pathogen attack. These responses are initiated when pathogen-derived molecules (elicitors) are recognized by the host. In order to create novel mechanisms for fire blight resistance in pear, we have generated transgenic pears expressing the elicitor harpin N_ea from Erwinia amylovora under the control of the constitutive promoter CaMV35S. The transient expression of hrpN _Ea in pear cells did not provoke any apparent damage. Therefore, stable constitutive expression of hrpN _Ea was studied in seventeen transgenic clones of the very susceptible cultivar “Passe Crassane.” Most transgenic clones displayed significant reduction of susceptibility to fire blight in vitro when inoculated by E. amylovora, which was positively correlated to their degree of expression of the transgene hrpN _Ea . These results indicate that ectopic expression of a bacterial elicitor such as harpin N_ea is a promising way to improve pear resistance to fire blight.     

Multicolor FISH mapping of the dioecious model plant,<Emphasis Type="Italic"> Silene latifolia</Emphasis>

Silene latifolia is a key plant model in the study of sex determination and sex chromosome evolution. Current studies have been based on genetic mapping of the sequences linked to sex chromosomes with analysis of their characters and relative positions on the X and Y chromosomes. Until recently, very few DNA sequences have been physically mapped to the sex chromosomes of S. latifolia. We have carried out multicolor fluorescent in situ hybridization (FISH) analysis of S. latifolia chromosomes based on the presence and intensity of FISH signals on individual chromosomes. We have generated new markers by constructing and screening a sample bacterial artificial chromosome (BAC) library for appropriate FISH probes. Five newly isolated BAC clones yielded discrete signals on the chromosomes: two were specific for one autosome pair and three hybridized preferentially to the sex chromosomes. We present the FISH hybridization patterns of these five BAC inserts together with previously described repetitive sequences (X-43.1, 25S rDNA and 5S rDNA) and use them to analyze the S. latifolia karyotype. The autosomes of S. latifolia are difficult to distinguish based on their relative arm lengths. Using one BAC insert and the three repetitive sequences, we have constructed a standard FISH karyotype that can be used to distinguish all autosome pairs. We also analyze the hybridization patterns of these sequences on the sex chromosomes and discuss the utility of the karyotype mapping strategy presented to study sex chromosome evolution and Y chromosome degeneration.Communicated by J.S. Heslop-Harrison     

Genetic processes in intergeneric cell hybrids Atropa + Nicotiana

Summary The genetic constitution of the cell hybrids Atropa belladonna + Nicotiana chinensis, obtained by cloning of individual heteroplasmic protoplast fusion products (Gleba et al. 1982) and cultured in vitro for 12 months, has been studied. The study comprised 11 hybrid cell clones of independent origin and included analysis of a) chromosome number, size, morphology, and relative position in metaphase plates, b) multiple molecular forms of the enzymes esterase and amylase, and c) relative nuclear DNA content. The data obtained permit us to conclude that, after one year of unorganized growth in vitro, the cells of most (8) clones had retained chromosomes of both parents, while species-specific elimination of nearly all Atropa chromosomes had occurred in three clones. About half of the non-segregating clones possess 120–150 chromosomes including 50–70 of Atropa and 50–90 of Nicotiana. Other clones are polyploid and possess 200–250 chromosomes with a predominance of either Atropa or Nicotiana chromosome types. Only a few chromosomal changes (reconstituted chromosomes, ring chromosomes) have been detected. In some metaphase plates, chromosomes of the two parents tend to group separately, indicating non-random arrangement of chromosomes of the two parents within the hybrid nucleus. Cytophotometric studies of the relative nuclear DNA content showed that distribution histograms for cell clones were similar to those of non-hybrid cultured cells. Cell populations were relatively homogenous and do not indicate any genetic instability as a result of hybridization between remote plant species. Biochemical analysis of isoenzyme patterns confirmed that in most cell clones, species-specific multiple molecular forms of esterase and amylase from both parents were present, i.e. genetic material of both parental species was expressed in the cell hybrids.Dedicated to Professor G. Melchers with gratitude     

Transfer of resistance to the beet cyst nematode (Heterodera Schachtii Schm.) from Sinapis alba L. (white mustard) to the Brassica napus L. gene pool by means of sexual and somatic hybridization

Summary Sexual and somatic hybrid plants have been produced between Sinapis alba L. (white mustard) and Brassica napus L. (oil-seed rape), with the aim to transfer resistance to the beet cyst nematode Heterodera schachtii Schm. (BCN) from white mustard into the oil-seed rape gene pool. Only crosses between diploid accessions of S. alba (2n = 24, S_a1S_a1) as the pistillate parent and several B. napus accessions (2n = 38, AACC) yielded hybrid plants with 31 chromosomes. Crosses between tetraploid accessions of S. alba (2n = 48, S_a1S_a1S_a1S_a1) and B. napus were unsuccessful. Somatic hybrid plants were also obtained between a diploid accession of S. alba and B. napus. These hybrids were mitotically unstable, the number of chromosomes ranging from 56 to more than 90. Analysis of total DNA using a pea rDNA probe confirmed the hybrid nature of the sexual hybrids, whereas for the somatic hybrids a pattern identical to that of B. napus was obtained. Using chloroplast (cp) and mitochondrial (mt) DNA sequences, we found that all of the sexual F₁ hybrids and somatic hybrids contained cpDNA and mtDNA of the S. alba parent. No recombinant mtDNA or cpDNA pattern was observed. Three BC₁ plants were obtained when sexual hybrids were back-crossed with B. napus. Backcrossing of somatic hybrids with B. napus was not successful. Three sexual hybrids and one BC₁ plant, the latter obtained from a cross between a sexual hybrid and B. napus, were found to show a high level of BCN resistance. The level of BCN resistance of the somatic hybrids was in general high, but varied between cuttings from the same plant. Results from cytological studies of chromosome association at meiotic metaphase I in the sexual hybrids suggest partial homology between chromosomes of the AC and S_a1 genomes and thus their potential for gene exchange.     

Male and female segregation distortion for heterochromatic supernumerary segments on the S8 chromosome of the grasshopper Chorthippus jacobsi

The mode of inheritance of supernumerary segments located on three different chromosome pairs was investigated in controlled crosses with specimens of the grasshopper Chorthippus jacobsi. While extra segments located on chromosomes M₅ and M₆ showed Mendelian inheritance, that on S₈ did not. Thus, the two supernumerary heterochromatic chromosome segments located distally on the S₈ chromosome accumulated through non-Mendelian transmission through both sexes. The observed transmission patterns may be explained by gametic selection for spermatozoa carrying segmented S₈ chromosomes, in addition to meiotic drive for segmented S₈ chromosomes in heterozygous females. The significance of these findings for the maintenance of these polymorphisms in natural populations is discussed.by S.A. Gerbi     

Genomic in situ hybridization (GISH) analyses of Thinopyrum intermedium, its partial amphiploid Zhong 5, and disease-resistant derivatives in wheat

Genomic in situhybridization (GISH) to root-tip cells at mitotic metaphase, using genomic DNA probes from Thinopyrum intermedium and Pseudoroegneria strigosa, was used to examine the genomic constitution of Th. intermedium, the 56-chromosome partial amphiploid to wheat called Zhong 5 and disease-resistant derivatives of Zhong 5, in a wheat background. Evidence from GISH indicated that Th. intermedium contained seven pairs of St, seven J^S and 21 J chromosomes; three pairs of Th. intermedium chromosomes with satellites in their short arms belonging to the St, J, J genomes and homoeologous groups 1, 1, and 5 respectively. GISH results using different materials and different probes showed that seven pairs of added Th. intermedium chromosomes in Zhong 5 included three pairs of St chromosomes, two pairs of J^S chromosomes and two pairs of St-J^S reciprocal tanslocation chromosomes. A pair of chromosomes, which substituted a pair of wheat chromosomes in Yi 4212 and in HG 295 and was added to 21 pairs of wheat chromosomes in the disomic additions Z1, Z2 and Z6, conferred BYDV-resistance and was identical to a pair of St-J^S tanslocation chromosomes (StJ^S) in Zhong 5. The StJ^S chromosome had a special GISH signal pattern and could be easily distinguished from other added chromosomes in Zhong 5; it has not yet been possible to locate the BYDV-resistant gene(s) of this translocated chromosome either in the St chromosome portion belonging to homoeologous group 2 or in the J^S chromosome portion whose homoeologous group relationship is still uncertain. Among 22 chromosome pairs in disomic addition line Z3, the added chromosome pair had satellites and belonged to the St genome and homoeologous group 1. Disomic addition line Z4 carried a pair of added chromosomes which was composed of a group-7 J^S chromosome translocated with a wheat chromosome; this chromosome was different to 7 Ai-1, but was identical to 7 Ai-2. The leaf rust and stem rust resistance genes were located in the distal region of the long arm, whereas the stripe rust resistance gene(s) was located in the short arm or in the proximal region of the long arm of 7 Ai-2. A pair of J^S-wheat translocation chromosomes, which originated from the WJ^S chromosomes in Z4, was added to the disomic addition line Z5; the added chromosomes of Z5 carried leaf and stem rust resistance but not stripe rust resistance; Z5 is a potentially useful source for rust resistance genes in wheat breeding and for cloning these novel rust-resistant genes. GISH analysis using the St genome as a probe has proved advantageous in identifying alien Th. intermedium in wheat. Received: 17 May 1999 / Accepted: 22 June 1999     

An S-RNase promoter from Nicotiana alata functions in transgenic N. alata plants but not Nicotiana tabacum

Nicotiana tabacum and Nicotiana alata plants were transformed with genomic clones of two S-RNase alleles from N. alata. Neither the S ₂ clone, with 1.6 kb of 5 sequence, nor the S ₆ clone, with 2.8 kb of 5 sequence, were expressed at detectable levels in transgenic N. tabacum plants. In N. alata, expression of the S ₂ clone was not detected, however the S ₆ clone was expressed (at low levels) in three out of four transgenic plants. An S ₆-promoter-GUS fusion gene was also expressed in transgenic N. alata but not N. tabacum. Although endogenous S-RNase genes are expressed exclusively in floral pistils, the GUS fusion was expressed in both styles and leaves.     

Generating stable chinese hamster ovary cell clones to produce a truncated SARS‐CoV spike protein for vaccine development

The spike (S) protein of the severe acute respiratory syndrome coronavirus (SARS‐CoV) is important for vaccine development. S_TR2 (an 88 kDa truncated SARS‐CoV TW1 S protein carrying the S fragments S‐74‐253, S‐294‐739, and S‐1129‐1255) is capable of expressing a major form of glycoprotein as endo H‐sensitive (～115 kDa) in CHO cells. To establish stable expressing cell clones, we transfected CHO/dhFr‐cells with the amplifiable vectors ISID (IRES‐driven dhfr) and ISIZ (SV40‐driven dhfr) to select stepwise MTX, and observed enhanced ～115 kDa glycoform generation through gene amplification. Following stepwise MTX selection, we compared gene amplification levels between two vectors in engineered CHO cell chromosomes. These results confirm that the IRES‐driven dhfr promoter generates greater gene amplification, which in turn enhances S_TR2 expression. Our results indicate that the ～115 kDa glycoform of S_TR2 protein was capable of increasing after gene amplification. The S_TR2 glycoform did not change between suspension and serum‐free cultures, suggesting that the stable and amplified cell clones analyzed in this study have potential for producing homologous S_TR2 on a large scale. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010     

Identification of the different Brassica nigra chromosomes from both sets of B. oleracea-B. nigra and B. napus-B. nigra addition lines with a special emphasis on chromosome transmission and self-incompatibility

 The F₁ hybrids produced after crosses between B. gra and B. oleracea were backcrossed two or three times to B. oleracea. Among the 14 plants analysed, five were monosomic addition lines (2n=19), six were double monosomic addition lines (2n=20) and three had three or four additional chromosomes. From these lines, 14 isozyme and 80 RAPD loci were localized on the eight chromosomes of B. nigra. The comparison between B. napus-B. nigra, from which five B. nigra chromosomes were already described, and the new set of B. oleracea-B. nigra addition lines was performed using five isozyme and 22 common RAPD loci. The homology of the common RAPD loci was confirmed by hybridization of the two sets of addition lines as well as the presence of duplicated loci on different chromosomes. For the five added chromosomes available on the two genetic backgrounds, i.e. B. napus and B. oleracea, using isozyme markers, the chromosome transmission rate was studied from backcross progeny using the recurrent parent either as male or as female and from the selfing of monosomic addition lines. For each chromosome, no difference was detected between male and female transmission except for chromosome 3. This latter presented a percentage of female transmission of around 20%, close to the ones observed for the other chromosomes, but a very low male transmission (1.3%). The analysis from restriction enzyme digests of PCR products, obtained from primers selected in highly conserved regions of self-incompatible genes, suggested that the chromosome 3 probably carried the SLG-B. nigra locus. Received: 25 September 1996 / Accepted: 18 October 1996     

Unequal chromosome division and inter-genomic translocation occurred in somatic cells of wheat–rye allopolyploid

Newly synthesized wheat–rye allopolyploids were investigated by genomic in situ hybridization, over the first, second, third and fourth allopolyploid generations. Inter and intra chromosome connections were observed in 12 root-tip cells of CA4.4.7 (S₂ generation), and translocations between wheat and rye chromosomes were also detected in five root-tip cells. In root-tip cells of CA4.4.7.5 and CA4.4.7.2.2 (S₃ and S₄ generation), the chromosome connections occurred again, a dissociative small rye segment was detected in seven cells of CA4.4.7.5. In plants MSV6.1 and MSV6.5 (S₁ generation), almost half of the root-tip cells contained 13 rye chromosomes and the rest held 12 rye chromosomes, and all the cells of the two plants contained 42 wheat chromosomes. Five pairing configurations of rye chromosomes, including 5 II + 3 I, 6 II + 1 I, 6 II, 5 II + 2 I and 4 II + 4 I, were observed in pollen mother cells of the two plants. The two plants’ progeny, including S₂, S₃, and S₄ generation plants, contained 42 wheat chromosomes and 12 rye chromosomes. Therefore, the inter chromosome translocation and unequal chromosome division could occur in somatic cells of wide hybrids. The unequal chromosome division in somatic cell could induce chromosome elimination at the early stages of allopolyploidization.     

Solid state fermentation of Saccharum munja residues into food through Pleurotus cultivation

The technical feasibility of using Saccharum munja as a substrate for the cultivation of the oyster mushroom, Pleurotus sajor-caju, is evaluated. The biological efficiency of mushroom production is compared on different substances-S. munja, S. munja plus paddy straw, and paddy straw. Although the efficiency is low on S. munja, the ready availability of this weed large areas holds a favourable option for its use in mushroom cultivation. The crude proteins, fats, carbohydrates, and energy values are also lower though the differences are not great. The degradation of three major components-cellulose, hemicellulose, and lignin has been observed, which proves P. sajor-caju to be a lignocellulolytic fungus. The nitrogen and mineral analysis of post-mushroom production S. munja (spent substrate) compares favorably with the dry cow-feed ration showing an enhanced protein content in the spent substrate.     

Isolation and identification of Triticum aestivum L. em. Thell. cv Chinese Spring-T. peregrinum Hackel disomic chromosome addition lines

Analyses of RFLPs, isozymes, morphological markers and chromosome pairing were used to isolate 12 Triticum aestivum cv Chinese Spring (genomes A, B, and D)-T. peregrinum (genomes S^v and U^v) disomic chromosome addition lines. The evidence obtained indicates that each of the 12 lines contains an intact pair of T. peregrinum chromosomes. One monosomic addition line, believed to contain an intact 6S^v chromosome, was also isolated. A CS-7U^v chromosome addition line was not obtained. Syntenic relationships in common with the standard Triticeae arrangement were found for five of the seven S^v genome chromosomes. The exceptions were 4S^v and 7S^v. A reciprocal translocation exists between 4S¹ and 7S¹ in T. longissimum and evidence was obtained that the same translocation exists in T. peregrinum. In contrast, evidence for syntenic relationships in common with the standard Triticeae arrangements were found for only one U^v chromosome of T. peregrinum.; namely, chromosome 2U^v. All other U^v genome chromosomes are involved in at least one translocation, and the same translocations were found in the U genome of T. umbellulatum. Evidence was also obtained indicating that the centromeric regions of 4U and 4U^v are homoeologous to the centromeric regions of Triticeae homoeologous group-6 chromosomes, that the centromeric regions of 6U and 6U^v are homoeologous to the centromeric regions of group-4 chromosomes, and that 4U and 4U^v are more closely related overall to Triticeae homoeologous group-6 chromosomes than they are to group-4 chromosomes.     

Development of sequence characterized DNA markers linked to leaf rust (<Emphasis Type="Italic">Hemileia vastatrix</Emphasis>) resistance in coffee (<Emphasis Type="Italic">Coffea arabica</Emphasis> L.)

Coffee leaf rust due to Hemileia vastatrix is one of the most serious diseases in Arabica coffee (Coffea arabica). A resistance gene (S_H3) has been transferred from C. liberica into C. arabica. The present work aimed at developing sequence-characterized genetic markers for leaf rust resistance. Linkage between markers and leaf rust resistance was tested by analysing two segregating populations, one F₂ population of 101 individuals and one backcross (BC₂) population of 43 individuals, derived from a cross between a susceptible and a SH3-introgressed resistant genotype. A total of ten sequence-characterized genetic markers closely associated with the S_H3 leaf rust resistance gene were generated. These included simple sequence repeats (SSR) markers, sequence-characterised amplified regions (SCAR) markers resulting from the conversion of amplified fragment length polymorphism (AFLP) markers previously identified and SCAR markers derived from end-sequences of bacterial artificial chromosome (BAC) clones. Those BAC clones were identified by screening of C. arabica genomic BAC library using a cloned AFLP-marker as probe. The markers we developed are easy and inexpensive to run, requiring one PCR step followed by gel separation. While three markers were linked in repulsion with the S_H3 gene, seven markers were clustered in coupling around the S_H3 gene. Notably, two markers appeared to co-segregate perfectly with the S_H3 gene in the two plant populations analyzed. These markers are suitable for marker-assisted selection for leaf rust resistance and to facilitate pyramiding of the S_H3 gene with other leaf rust resistance genes.     

Introgression of group 4 and 7 chromosomes of <Emphasis Type="Italic">Ae</Emphasis>. <Emphasis Type="Italic">peregrina</Emphasis> in wheat enhances grain iron and zinc density

Dietary deficiency of iron and zinc micronutrients affects more than two billion people worldwide. Breeding for micronutrient-dense crops is the most sustainable and cost-effective approach for alleviation of micronutrient malnutrition. Three accessions of Aegilops peregrina (Hack.) Maire & Weill (2n = 28, U^PU^PS^PS^P), selected for high grain iron and zinc concentration were crossed with Triticum aestivum L. cv. Chinese Spring (Ph ^I ). The sterile F₁ hybrids were backcrossed with elite wheat cultivars to get fertile BC₂F₂ derivatives. Some of the fertile BC₂F₂ derivatives showed nearly 100% increase in grain iron and more than 200% increase in grain zinc concentration compared to the recipient wheat cultivars. The development of derivatives with significantly higher grain micronutrients, high thousand-grain weight and harvest index suggests that the enhanced micronutrient concentration is due to the distinct genetic system of Ae. peregrina and not to the concentration effect. Genomic in situ hybridization, comparison of introgressed chromosomes with the standard karyotype of Ae. peregrina and simple sequence repeat marker analysis revealed the introgression of 7S^P chromosomes in five selected derivatives, 7U^P in four, group 4 and 4S^P in three and a translocated 5U^P of Ae. peregrina in one of the selected derivatives. Molecular marker analysis using the introgressed chromosome markers indicated that two of the BC₂F₃ progenies were stabilized as disomic addition lines. It could, therefore, be concluded that the group 4 and 7 chromosomes of Ae. peregrina carry the genes for high grain iron and zinc concentration.     

Genet Distribution of Ectomycorrhizal Fungus Suillus grevillei Populations in Two Larix kaempferi Stands over Two Years

Suillus grevillei in two Larix kaempferi stands was determined over two years by inter-simple sequence repeat (ISSR) polymorphism analysis using primers, (GTG)₅, (GCC)₅ and (GACA)₄. Thirty-five genets were identified from 67 sporocarps at the older stand (stand A in which the distribution of S. grevillei genet in 1997 was analyzed previously) in 1998, and 14 genets from 52 sporocarps at the younger stand (stand B) in 1997 and 1998. The characteristics of S. grevillei genets in stand A in 1998 were similar to those in 1997. A single genet was represented by 1.8 and 3.7 sporocarps on average in stands A and B, respectively. In stand A, 42 out of 61 genets, i.e., about 70% were represented by individual sporocarps compared to five out of 14 genets, i.e., about 35% in stand B. The largest and the average genet sizes was 6.8 m and less than 1 m in stand A, and 11 m and 2.3 m in stand B, respectively. A t-test showed the genet size in stand A to be significantly smaller than that in stand B. The above results indicate that the smaller genets of the S. grevillei population in stand A might be due to environmental conditions not genetic traits specific to this species. Observations over two years showed that although some genets formed sporocarps in both 1997 and 1998, many formed sporocarps only in one of the two years. Emerging positions of sporocarps in 1997 and 1998, which belonged to the same genet, were similar but not identical, about 2 m apart, suggesting mobility in the subterranean parts of ECM fungal genets. Received 10 April 2000/ Accepted in revised form 31 August 2000     

Recent changes in the distribution of carboxylesterase genes and associated chromosomal rearrangements in Greek populations of the tobacco aphid Myzus persicae nicotianae

We present data on the frequency of amplified E4 and FE4 carboxylesterase genes in Myzus persicae s.l. clones collected during the years 2002–2007 and 2012 in Greece. Most clones were of the tobacco aphid, Myzus persicae nicotianae. Samples from 2012 were genotyped with microsatellite DNA markers and a number of them were karyotyped. Aphid clones with amplified FE4 genes predominated in all years, whereas E4 was present in only 3.5% of all samples and always occurred in clones with FE4. Most of the clones examined showed high carboxylesterase activity levels (R2 resistant category). The results showed marked changes in the frequencies of the two carboxylesterase genes in the tobacco aphid populations compared to published data that were collected in Greece in the mid 1990s, when E4 was recorded on its own in 20% of all samples and in 32% of samples from tobacco. A parallel change in karyotype was also observed because the A1,3 translocation, which had a worldwide association with amplified E4 genes in the 1990s, was not detected in the clones analyzed in 2012. Possible causes for these changes are discussed, although selection as a result of pest management practices appears to be the major one. Novel chromosomal rearrangements were also found in M. persicae nicotianae clones. These rearrangements could be a result of clastogenic effects of nicotine, which could persist because of the holocentric nature of aphid chromosomes. The results are discussed in relation to rapid evolution events that have taken place in the tobacco aphid in Greece during the last two decades. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 455–470.     

Physical mapping and microsynteny of Brassica rapa ssp. pekinensis genome corresponding to a 222 kbp gene-rich region of Arabidopsis chromosome 4 and partially duplicated on chromosome 5

We constructed a bacterial artificial chromosome (BAC) library, designated as KBrH, from high molecular weight genomic DNA of Brassica rapa ssp. pekinensis (Chinese cabbage). This library, which was constructed using HindIII-cleaved genomic DNA, consists of 56,592 clones with average insert size of 115 kbp. Using a partially duplicated DNA sequence of Arabidopsis, represented by 19 and 9 predicted genes on chromosome 4 and 5, respectively, and BAC clones from the KBrH library, we studied conservation and microsynteny corresponding to the Arabidopsis regions in B. rapa ssp. pekinensis. The BAC contigs assembled according to the Arabidopsis homoeologues revealed triplication and rearrangements in the Chinese cabbage. In general, collinearity of genes in the paralogous segments was maintained, but gene contents were highly variable with interstitial losses. We also used representative BAC clones, from the assembled contigs, as probes and hybridized them on mitotic (metaphase) and/or meiotic (leptotene/pachytene/metaphase I) chromosomes of Chinese cabbage using bicolor fluorescence in situ hybridization. The hybridization pattern physically identified the paralogous segments of the Arabidopsis homoeologues on B. rapa ssp. pekinensis chromosomes. The homoeologous segments corresponding to chromosome 4 of Arabidopsis were located on chromosomes 2, 8 and 7, whereas those of chromosome 5 were present on chromosomes 6, 1 and 4 of B. rapa ssp. pekinensis.