Mutation in Flower Colour and Shape of Chrysanthemum morifolium Induced by γ-Radiation

Flowers of Chrysanthemum morifolium Ramat cv. Lalima were greyed red and florets were flat spoon shaped. Ray florets after inoculation on the Murashige and Skoog's medium supplemented with 1.07 μM α-naphthaleneacetic acid and 8.87 μM benzyladenine were irradiated with γ-radiation (0.5 Gy and 1 Gy). All the regenerated shoots either from control or from γ-irradiated florets were isolated, rooted and transplanted in the field after hardening. Two mutants were obtained in the γ-irradiated plants (0.5 Gy). Both the mutants were yellow coloured but one having flat spoon shaped ray florets similar to the original cultivar, while the other having tubular florets. Both the mutants were propagated vegetatively and have produced true-to-type flowers. This revised version was published online in July 2006 with corrections to the Cover Date.     

Primary and secondary somatic embryogenesis in Chrysanthemum (Chrysanthemum morifolium) cv. ‘Baeksun’ and assessment of ploidy stability of somatic embryogenesis process by flow cytometry

We developed an efficient and simple system for inducing somatic embryogenesis and regenerating plantlets from petal explant of Chrysanthemum (Chrysanthemum morifolium) cv. ‘Baeksun’. Somatic embryogenesis was induced from petal explants on the Murashige and Skoog (MS) medium supplemented with 1.0 mg l^?1 2,4-dichlorophenoxyacetic acid (2,4-D) and 3.0 mg l^?1 6-benzyladenine (BA), yielding the highest mean number of embryos (56.3) per explant after 5 weeks of culture. We evaluated the effects of basal medium and various concentrations of sucrose on the proliferation of secondary somatic embryos. MS medium was observed to be more effective in promoting the proliferation of somatic embryos than half-strength Murashige and Skoog (1/2MS). In addition, 1 % sucrose was also found to be the best in induction of secondary embryogenesis. The highest germination rate (70 %) of the somatic embryos was observed on the MS medium containing 0.2 mg l^?1 α-naphthalene acetic acid and 1 g l^?1 activated charcoal (AC). Shoots elongated rapidly and roots developed well on hormone-free MS medium with 1 g l^?1 AC and successfully acclimated in the greenhouse. Flow cytometric analysis of the primary somatic embryos, secondary somatic embryos, and the somatic embryo-obtained plants along with the parent grown in the greenhouse showed that they all had same identical peaks, indicating that there was no variation of ploidy level during the regeneration process. We expect that our report would be useful for micropropagation and Agrobacterium-mediated genetic transformation studies of this cultivar.     

Quantitative trait loci for yield and yield components in an Oryza sativa×Oryza rufipogon BC2F2 population evaluated in an upland environment

An advanced backcross breeding strategy was used to identify quantitative trait loci (QTLs) associated with eight agronomic traits in a BC₂F₂ population derived from an interspecific cross between Caiapo, an upland Oryza sativa subsp. japonica rice variety from Brazil, and an accession of Oryza rufipogon from Malaysia. Caiapo is one of the most-widely grown dryland cultivars in Latin America and may be planted as a monoculture or in a multicropping system with pastures. The objectives of this study were: (1) to determine whether trait-enhancing QTLs from O. rufipogon would be detected in 274 BC₂F₂ families grown under the drought-prone, acid soil conditions to which Caiapo was adapted, (2) to compare the performance with and without pasture competition, and (3) to compare putative QTL-containing regions identified in this study with those previously reported for populations adapted to irrigated, low-land conditions. Based on analyses of 125 SSLP and RFLP markers distributed throughout the genome and using single-point, interval, and composite interval mapping, two putative O. rufipogon derived QTLs were detected for yield, 13 for yield components, four for maturity and six for plant height.We conclude that advanced backcross QTL analysis offers a useful germplasm enhancement strategy for the genetic improvement of cultivars adapted to stress-prone environments. Although the phenotypic performance of the wild germplasm would not suggest its value as a breeding parent, it is noteworthy that 56% of the trait-enhancing QTLs identified in this study were derived from O. rufipogon. This figure is similar to the 51% of favorable QTLs derived from the same parent in crosses with a high-yielding hybrid rice cultivar evaluated under irrigated conditions in a previous study. In conclusion, parallel studies in rice using AB-QTL analysis provide increasing evidence that certain regions of the rice genome are likely to harbor genes of interest for plant improvement in multiple environments. Received: 3 September 1999 / Accepted: 16 May 2000     

Developing stable progenies of ×Brassicoraphanus, an intergeneric allopolyploid between Brassica rapa and Raphanus sativus, through induced mutation using microspore culture

Induced mutations were used to improve the low seed fertility of an intergeneric allopolyploid, ‘Baemoochae,’ ×Brassicoraphanus, synthesized following hybridization between Brassica rapa and Raphanus sativus. The mutagen N-methyl-N-nitroso-urethane (NMU) was added to microspore cultures. Four lines of nine in the Mi₂ generation showed very high fertility under controlled pollination. The progeny lines (Mi₃) confirmed this result under open pollination, and excellent uniformity was observed in plants grown in the field, as well as in their AFLP profile. On attaining high fertility and uniformity, one of the lines was released to farmers as a new leafy vegetable crop. The original nine lines shared very similar AFLP banding patterns, without any large differences between the high and low seed fertility lines. Thus, mutation induction accelerated genetic stabilization of a newly synthesized allopolyploid, ×Brassicoraphanus.     

Isozyme Analysis of F 5 and BC 1F 4 from Cultivated Barley (Hordeum vulgare)× Roegneria ciliaris

栽培大麦,纤毛鹅观草,属间杂种,酯酶,过氧化物酶 ISOZYME ANALYSIS OF F5 AND BCiF4 FROM CULTIVATED BARLEY ( HORDEUM VULGARE ) ~ ROEGNERIA CILIARIS LI Wan-Ji LI Yi-Ping L1U Fang Abstract Esterase and peroxidase isozymes were analysed in the variants including 4 types, 16 lines of Fs, BC1F4 and the parents derived from cultivated barley ( Hordeum vulgare cv. Arupo) x Roegneria ciliaris (Trin.) Nevski in young roots, shoots, spikes and seeds. The zymogram patterns of esterase and peroxidase demonstrated that the 16 lines of F5 and BC1F4 had all or most bands of the cultivated barley parent cv. "Arupo", 1 to 3 bands from the male R. ciliaris, and new hybrid isozyme bands in various amount. Some bands of parent "Arupo" were lost. It suggested that the genetic substances come from R. ciliaris were stably inherited to the progenies of selfing and backcrossing, and there were some variations among the lines. There was certain relationship between isozyme variance and plant characters. Thus, in identifying the translocation lines by isozyme analysis, it would be preferable to study the various organ-specific isozymes or to trace one type of isozyme pattern in consequence.     

Increase in incidence of chromosome instability and non-conservative recombination between repeats in Saccharomyces cerevisiae hpr1Δ strains

Null hprl Δ strains show a large increase (up to 2000-fold) over wild type in the frequency of occurrence of deletions between direct repeats on three different chromosomes. However, we show that hprl Δ mutations have little or no effect on reciprocal exchange, gene conversion or unequal sister chromatid exchange, as determined using intrachromosomal, interchromosomal and plasmid-chromosome assay systems. A novel intrachromosomal recombination system has allowed us to determine that over 95% of deletions in hpr1 Δ strains do not occur by reciprocal exchange. On the other hand, hpr1 Δ strains show chromosome loss frequencies of up to 100 times the wild-type level. Our results suggest that yeast cells have a very efficient non-conservative recombination mechanism, dependent on RADI and RAD52, that causes deletions between direct DNA repeats, and this mechanism is strongly stimulated in hpr1 Δ strains. The results indicate that the Hpr1 protein is required for stability of DNA repeats and chromosomes. We propose that in the absence of the Hprl protein the cell destabilizes the genome by allowing the initiation of events that lead to deletions of sequences between repeats, and to chromosome instability. We discuss the roles that proteins such as Hprl have in maintaining direct repeats and in preventing non-conservative recombination and consider the importance of these functions for chromosome stability.     

Morphological characteristics of leaf epidermis and size variation of leaf,flower and fruit in different ploidy levels in Buddleja macrostachya （Buddlejaceae）

Buddleja macrostachya （Buddlejaceae） is a widespread shrub native to the Sino-Himalayan mountains and beyond. It has been found to occur at two ploidy levels, hexaploid, 2n=6x=114 and dodecaploid, 2n= 12x=228. To determine if morphological characters might be used as indicators of ploidy levels, we measured floral and fruit length, relative and absolute leaf size, trichome density on both leaf surfaces, and stomatal density and length in different populations orB. macrostachya. In general, flower and fruit length, absolute leaf size, and stomatal length in,eased with an increase at ploidy level （P〈0.01）, whereas adaxial cell and stomatal density decreased with an increase at ploidy level （P〈0.01）. We found no conspicuous differences in relative leaf size （P〉0.05） in different populations. Other characters studied such as trichome type, cuticular membrane and ornamentation of stomata, cell and stomatal shape, and anticlinal wall pattern were quite constant in this species. Thus it appears that flower and fruit length, absolute leaf size, and stomatal frequency and length can be used to distinguish hexaptoid from dodecaploid cytotypes either in the field or in herbarium specimens.     

Interleukin-1 α and β genes: linkage on chromosome 2 in the mouse

Two interleukin-1 polypeptides, and , are known, and cDNAs corresponding to each have been described. Genomic cloning and Southern blotting experiments suggest that in the mouse each is encoded by a gene present in one copy per haploid genome. Analysis of a panel of somatic cell hybrids carrying various mouse chromosomes on a constant Chinese hamster background indicates that both genes map to mouse chromosome 2. Further, analysis of the inheritance of DNA restriction fragment length polymorphisms associated with each gene in recombinant inbred strains of mice shows the two loci to be tightly linked to one another, and to lie approximately 4.7 centimorgans distal to B2m (beta-2 microglobulin). We have named the locus encoding IL-1 Il-1 and the locus encoding IL-1 Il-1b.     

Mapping through somatic cell hybrids and cDNA probes of protein C to chromosome 2, factor X to chromosome 13, and α1-acid glycoprotein to chromosome 9

Summary The previously unassigned gene coding for the anticoagulatory protein C has been mapped on chromosome 2 using a cDNA probe and genomic blots from a human-hamster somatic cell hybrid panel. The assignments of the genes coding for the coagulation factor X to chromosome 13, and for 1-acid glycoprotein to chromosome 9 have been confirmed using a similar direct approach.     

Non-random associations between Lap and Pept-1 loci and gene arrangements of chromosome O in D. subobscura — experiments in laboratory populations

In this paper the well-known non-random associations between Lap and Pept-1 loci and gene arrangements of chromosome O are studied in laboratory populations of D. subobscura. An increase of the frequency of the allele Lap ^1.00, towards an equilibrium point (0.70), was found to be associated with an increase of the gene arrangement O₃₊₄. This is an accordance to the associations found in natural populations. On the contrary no such an increase was observed in populations polymorphic for Lap and Pep-1 loci but homokaryotypic for gene arrangement O₃₊₄₊₈ differing in the initial allele frequencies at these loci. Although epistatic selection cannot be completely ruled out, our results are better explained under the assumption of neutrality.     

Epistasis between QTLs for bone density variation in Copenhagen × dark agouti F2 rats

The variation in several of the risk factors for osteoporotic fracture, including bone mineral density (BMD), has been shown to be strongly influenced by genetic differences. However, the genetic architecture of BMD is complex in both humans and in model organisms. We previously reported quantitative trait locus (QTL) results for BMD from a genome screen of 828 F2 progeny of Copenhagen and dark agouti rats. These progeny also provide an excellent opportunity to search for epistatic effects, or interaction between genetic loci, that contribute to fracture risk. Microsatellite marker data from a 20-cM genome screen was analyzed along with weight-adjusted bone density (DXA and pQCT) phenotypic data using the R/qtl software package. Genotype and phenotype data were permuted to determine genome-wide significance thresholds for the full model and epistasis (interaction) LOD scores corresponding to an alpha level of 0.01. A novel locus on chromosome 15 and a previously reported chromosome 14 QTL demonstrated a strong epistatic effect on BMD at the femur by DXA (LOD = 5.4). Two novel QTLs on chromosomes 2 and 12 were found to interact to affect total BMD at the femur midshaft by pQCT (LOD = 5.0). These results provide new information regarding the mode of action of previously identified QTL in the rat, as well as identifying novel loci that act in combination with known QTL or with other novel loci to contribute to BMD variation.     

Increase in incidence of chromosome instability and non-conservative recombination between repeats in Saccharomyces cerevisiae hpr1Δ strains

Null hprl strains show a large increase (up to 2000-fold) over wild type in the frequency of occurrence of deletions between direct repeats on three different chromosomes. However, we show that hprl mutations have little or no effect on reciprocal exchange, gene conversion or unequal sister chromatid exchange, as determined using intrachromosomal, interchromosomal and plasmid-chromosome assay systems. A novel intrachromosomal recombination system has allowed us to determine that over 95% of deletions in hpr1 strains do not occur by reciprocal exchange. On the other hand, hpr1 strains show chromosome loss frequencies of up to 100 times the wild-type level. Our results suggest that yeast cells have a very efficient non-conservative recombination mechanism, dependent on RADI and RAD52, that causes deletions between direct DNA repeats, and this mechanism is strongly stimulated in hpr1 strains. The results indicate that the Hpr1 protein is required for stability of DNA repeats and chromosomes. We propose that in the absence of the Hprl protein the cell destabilizes the genome by allowing the initiation of events that lead to deletions of sequences between repeats, and to chromosome instability. We discuss the roles that proteins such as Hprl have in maintaining direct repeats and in preventing non-conservative recombination and consider the importance of these functions for chromosome stability.     

Bradykinin and prostaglandin E1, E2 and F2α-induced macromolecular leakage in the hamster cheek pouch

The hamster cheek pouch prepared for intravital observations on macromolecular permeability with fluorescein labelled dextran was used in four series of 5 hamsters each, all pretreated with indomethacin. Bradykinin, PGE₁, PGE₂ and PGF_2α increased macromolecular leakage at postcapillary venules, and this leakage was reversible on removal of agent. A linear relation was found between the logarithmic value of dose of bradykinin and the mean number of leakage sites. No tachyphylaxis to bradykinin was seen. The effect of either PGE₁, PGE₂ or PGF_2α applied simultaneously with bradykinin was to significantly (p<0.05) potentiate the bradykinin response. Bradykinin and these prostaglandins appeared to have the same site of action for their effect of increasing permeability, e.g. the postcapillary venule.     

Genetic association of IDE,POU2F1, PON1, IL1α and IL1β with type 2 diabetes in Pakistani population

A number of genes are known to be involved in glucose homeostasis. Mutations and polymorphisms in candidate genes may effect insulin production, action or resistance. This study was designed to report the association of genetic polymorphism with the type 2 diabetes (T2D) in Pakistani population. A total of 458 subjects (case n = 288, control n = 170) participated in the study. Nine single nucleotide polymorphisms were investigated in genes IDE (rs6583813 C>T, rs7910977 C>T), POU2F1 (rs3767434 A>T, rs10918682 A>T, rs2146727 A>G), WFS1 (rs734312 A>G), PON1 (rs854560 T>A), IL1α (rs1800587 C>T) and IL1β (rs1143634 C>T). Genotyping was performed by DNA sequencing after nested polymerase chain reaction of targeted regions. Results indicated that rs7910977 in IDE showed significant association with the development of T2D [P = 0.012, OR 1.677 (95 % CI 1.112–2.438)]. The rs10918682 in POU2F1 was associated with T2D [P < 0.001, OR 3.606 (95 % CI 2.165–6.005)]. The rs854560 in PON1was associated with incidences of T2D and increased the risk of cardiovascular complications [P = 0.031, OR 0.663 (95 % CI 0.455–0.965)] in diabetics. The rs734312 from WFS1 gene was associated with diabetes at genotype level (P < 0.01). Haplotype analysis of rs1800587–rs1143634 depicted CC haplotype increased the susceptibility to diabetes (P < 0.05). Haplotype GAA from rs2146727–10918682–rs3767434 was protective against diabetes (P < 0.01) and GGA exhibited the association with T2D (P < 0.01). Haplotype CT from rs6583813–rs7910977 was protective against diabetes (P = 0.02). Our study provided evidence to IDE, PON1, WFS1, POU2F1, IL1α and IL1β associated with T2D in Pakistanis.     

Post-zygotic gametic selection due to endosperm balance number explains unusual chromosome numbers of 3×× 2× progeny in Solanum

 Crosses between triploid and diploid genotypes are usually the best sources of trisomics in potato as well as in several other crop species. However, 3×× 2× crosses between triploid (2n=3×=36; 2EBN) Solanum commersonii-S. tuberosum hybrids and diploid (2n= 2×=24; 2EBN) genotypes gave progenies with a high number of extra chromosomes, 29–36, suggesting that only eggs with 17–24 chromosomes produced embryos that reached full development. Our hypothesis is that although triploids produce eggs with a range of chromosome numbers, 3×× 2× crosses involving a 2×(2EBN) parent favor eggs with a high chromosome number. These eggs have higher probabilities of possessing the same endosperm balance number (EBN) value (i.e. 1) of gametes produced by the 2EBN diploid parent to give the required 2:1 maternal to paternal EBN ratio in the hybrid endosperm. Under this model, trisomics are produced only if the diploid parent has an EBN of 1. Based on our results and those reported in the literature, it is proposed that in 3×(2EBN) × 2×(2EBN) crosses the endosperm balance number exercises negative selection for gametes with a low chromosome number, and a corresponding low EBN, and positive selection for gametes with a high chromosome number and EBN. Received: 2 April 1998 / Revision accepted: 27 October 1998     

Why are there so many mimicry rings? Correlations between habitat,behaviour and mimicry in Heliconius butterflies

In the new world tropics there is an extravagant array of sympatric butterfly mimicry rings. This is puzzling under strictly coevolutionary (Müllerian) mimicry: all unpalatable species should converge as ‘co-mimics' to the same pattern. If mimicry has usually evolved in unpalatable species by one-sided (Batesian) evolution, however, it is easy to see that mimicry rings centred on different models could remain distinct. If mimicry rings were also segregated by habitat, a diversity of mimicry rings could be stabilized. In this paper we report correlations between behaviour and mimicry of nine unpalatable Heliconius species. It is already known that co-mimics fly in similar habitats, and non-mimics fly in different habitats, although there is much overlap. Contrary to a previous report, we find little difference in flight heights of heliconiine mimicry rings; all species fly from ground level to the canopy. However, co-mimics roost at night in similar habitats and at similar heights above the ground, but in different habitats and at different heights from species in other mimicry rings. Heliconius (especially the erato taxonomic group) are renowned for roosting gregariously; and co-mimics roost gregariously with each other more often than with non-mimics. Gregarious roosting is therefore common between species, as well as within species. There are thus strong links between mimicry and behavioural ecology in Heliconius. The paradoxical correlation between nocturnal roosting and visual mimicry is presumably explained by bird predation at dusk when roosts are forming, or at dawn before they have disbanded. Direct evidence of predation is lacking, but there are high rates of disturbance by birds at these times. These results, together with knowledge of the phylogeny of Heliconius, suggest that species from the melpomene-group of Heliconius have radiated to occupy mimetic niches protected by model species in the Ithomiinae and the erato-group of Heliconius. A variety of sympatric mimicry rings is apparently maintained because key models fail to converge, while more rapidly-evolving unpalatable mimics evolve towards the colour patterns of the models. The maintenance of mimetic diversity would be aided by the habitat and behavioural differences between mimicry rings revealed here, provided that different predators are found in different habitats. This explanation for the maintenance of multiple mimicry rings is more plausible for Heliconius mimicry than alternatives based on visual mating constraints, thermal ecology, or camouflage.     

Arabidopsis S6 kinase mutants display chromosome instability and altered RBR1�CE2F pathway activity

The 40S ribosomal protein S6 kinase (S6K) is a conserved component of signalling pathways controlling growth in eukaryotes. To study S6K function in plants, we isolated single‐ and double‐knockout mutations and RNA‐interference (RNAi)‐silencing lines in the linked Arabidopsis S6K1 and S6K2 genes. Hemizygous s6k1s6k2/++ mutant and S6K1 RNAi lines show high phenotypic instability with variation in size, increased trichome branching, produce non‐viable pollen and high levels of aborted seeds. Analysis of their DNA content by flow cytometry, as well as chromosome counting using DAPI staining and fluorescence in situ hybridization, revealed an increase in ploidy and aneuploidy. In agreement with this data, we found that S6K1 associates with the Retinoblastoma‐related 1 (RBR1)–E2FB complex and this is partly mediated by its N‐terminal LVxCxE motif. Moreover, the S6K1–RBR1 association regulates RBR1 nuclear localization, as well as E2F‐dependent expression of cell cycle genes. Arabidopsis cells grown under nutrient‐limiting conditions require S6K for repression of cell proliferation. The data suggest a new function for plant S6K as a repressor of cell proliferation and required for maintenance of chromosome stability and ploidy levels.