Molecular mapping of a new gene Rrs4 CI 11549 for resistance to barley scald (Rhynchosporium secalis)

Doubled haploid (DH) progeny from a cross between the scald susceptible barley (Hordeum vulgare L.) cultivar Ingrid and the resistant accession CI 11549 (Nigrinudum) was evaluated for resistance in the pathogen Rhynchosporium secalis (Oudem) J.J. Davis. Two linked and incompletely dominant loci confer resistance CI 11549 against isolate 4004. One is an allele at the complex Rrs1 locus on chromosome 3H close to the centromere; the other is located 22 cM distally on the long arm. The latter locus is designated Rrs4. In BC₃-lines into Ingrid from CI 2222 (another Nigrinudum) resistance seems governed by one locus close to the telomeric region of chromosome 7H, probably allelic to Rrs2. In neither case did we find any trace of the recessive gene rh8 reported to be present in Nigrinudum. Various resistance donors of Ethiopian origin designated as Nigrinudum, Jet or Abyssinian were identical to a great extent with respect to markers, but differed in resistance to different isolates of scald or in barley yellow dwarf virus (BYDV) resistance. The implications for their use as differentials in scald tests and screening of germplasm collections are discussed.     

The mitochondrial membrane potential (deltapsi(m)) in apoptosis; an update

Mitochondrial dysfunction has been shown to participate in the induction of apoptosis and has even been suggested to be central to the apoptotic pathway. Indeed, opening of the mitochondrial permeability transition pore has been demonstrated to induce depolarization of the transmembrane potential (_m), release of apoptogenic factors and loss of oxidative phosphorylation. In some apoptotic systems, loss of _m may be an early event in the apoptotic process. However, there are emerging data suggesting that, depending on the model of apoptosis, the loss of _m may not be an early requirement for apoptosis, but on the contrary may be a consequence of the apoptotic-signaling pathway. Furthermore, to add to these conflicting data, loss of _m has been demonstrated to not be required for cytochrome c release, whereas release of apoptosis inducing factor AIF is dependent upon disruption of _m early in the apoptotic pathway. Together, the existing literature suggests that depending on the cell system under investigation and the apoptotic stimuli used, dissipation of _m may or may not be an early event in the apoptotic pathway. Discrepancies in this area of apoptosis research may be attributed to the fluorochromes used to detect _m. Differential degrees of sensitivity of these fluorochromes exist, and there are also important factors that contribute to their ability to accurately discriminate changes in _m.     

Inheritance and linkage of isozyme loci in almond

The segregation of seven isozyme marker genes was investigated using eight controlled crosses in almond. The cultivar Nonpareil was the maternal parent in all crosses. Pollination was achieved using eight different cultivars, and a total of 3200 individual kernels were assessed. For each isozyme the goodness-of-fit test was used to test for departure from the expected frequencies assuming Mendelian inheritance. Given a higher than expected number of significant results for individual isozymes, independent segregation between pairs of isozymes was tested using the chi-square statistic on the resulting two-way contingency tables. In all crosses a highly significant association (P value< 0.001) was observed between (1) the AAT- 1 and IDH isozymes loci and (2) the LAP-1 and PGM-2 isozymes loci, which leads to the conclusion that the respective isozyme pairs are linked.In addition, a significant association (P value < 0.001) was observed between LAP-1 and GPI-2 when the pollen sources were Fritz, Mission, or Price, but this could not be tested for the remaining five pollen sources, Carmel, Grant, Keane, Ne plus Ultra, Peerless, because they are homozygous at these loci. If LAP-1 is linked with GPI-2 and PGM-2, it might be expected that we should find evidence of linkage between GPI-2 and PGM-2. The lack of a significant association between these two isozymes suggests that LAP-1 is located centrally on the chromosome. These three pairs of linked loci are the first to be reported in almond.     

Is repetitive DNA involved in male gametogenesis ofNarcissus papyraceus?

Summary The male gametophyte of the Spermatophyta is of particular interest when studying quantitative modifications of repetitive DNA which accompany plant differentiation. In fact, this well documented system offers the opportunity to investigate the phenomenon at the nuclear level. In particular, it permits comparison between single haploid nuclei which, though derived from the same mitotic division, have different, well-defined morphological and functional processes. The aim of the present work was to investigate the behaviour of repetitive DNA during male gametogenesis inNarcissus papyraceus. By the use of A+T and G+C specific fluorochromes (DAPI and Chromomycin A₃), and by in situ DNA digestion with appropriate restriction endonucleases (Eco RI and Hae III), it is shown that during the course of gametogenesis, generative and vegetative nuclei behave differently with respect to particular sections of the genome. Characteristic agglomerations of specific A+T rich DNA sequences can be observed, localized by the two distal ends of the spindle-shaped generative nucleus. The surface area occupied by the agglomerations differs significantly at the ends in all observed cases. The above agglomerations are present in most of the generative nuclei and are probably composed of repetitive DNA sequences. Some embryological questions are discussed in the light of these results.Abbreviations DAPI 4,6-diamidino-2-phenylindole - Eco RI Eco RI with star activity (N/AATTN) Dedicated to Prof. E. Battaglia on the occasion of his 75th birthday     

Identification and confirmation of three neutral alleles conferring wide compatibility in inter-subspecific hybrids of rice (Oryza sativa L.) using near-isogenic lines

Wide-compatibility varieties (WCVs) are a special class of rice germplasm that is able to produce fertile hybrids when crossed to both indica and japonica subspecies. Previous studies determined Dular and 02428 as two WCVs and identified a number of QTLs as having large effects on fertility of inter-subspecific hybrids. In this study, we developed five near-isogenic lines (NILs) for three of the QTLs, f5, f6 and S5, by backcrossing and marker-assisted selection, using Dular and 02428 as the donors and Zhenshan 97 as the recipient. Three of the NILs each carried one introgressed allele, and two NILs each carried two introgressed alleles in combinations. The NILs were testcrossed to an indica tester Nanjing 11 and a japonica tester Balilla. The results showed that the f5 allele from Dular (f5-Du) is a neutral allele conferring wide compatibility, with a large effect on both pollen and spikelet fertility, and the f6 allele from Dular (f6-Du) is a neutral allele for spikelet fertility with smaller effect. The S5 allele from 02428 (S5-08) was confirmed to be a neutral allele for spikelet fertility. It is likely that f6 and S5 are the same locus as deduced by their genomic locations and effects. The results also showed that even in combination, two neutral alleles of different loci were not able to produce normal fertility hybrids in typical indica–japonica crosses. The implications of the findings in rice breeding programs are discussed.     

Effect of Gamma Irradiation on Embryogenic Avocado Cultures and Somatic Embryo Development

Embryogenic avocado cultures were exposed to ionizing irradiation in order to determine its effect on proliferation and subsequent somatic embryo development. The approximate PD₅₀ as determined by linear regression is 35 Gy 2 weeks after irradiation for Fuerte 2.11.1 and 4 weeks after irradiation for T362 2.11.1. Irradiation of embryogenic cultures did not significantly affect the number of early stage Fuerte 2.11.1 somatic embryos that developed directly from irradiated cultures; however, 10–50 Gy inhibited somatic embryo development. Irradiation of T362 2.11.1 embryogenic cultures at 25–50 Gy inhibited the number of intermediate and mature stages of somatic embryos that developed directly from irradiated cultures, and 50 Gy inhibited somatic embryo maturation. Inhibition of somatic embryo development could be partially offset by proliferation of irradiated embryogenic cultures as suspensions. Irradiation up to 10 Gy significantly increased the number of mature Fuerte 2.11.1 somatic embryos that developed from suspension cultures. Irradiation with doses up to 25 Gy stimulated development of heart stage T362 2.11.1 somatic embryos; however, mature somatic embryo development was suppressed at dosages of 10 Gy and greater.     

Evidence of β-carotene 7,8(7′,8′) oxygenase (β-cyclocitral,crocetindial generating) in Microcystis

A -carotene oxygenase is described which occurs in the Cyanobacterium Microcystis. It cleaves -carotene and zeaxanthin specifically at the positions 7,8 and 7,8, while echinenone and myxoxanthophyll are not affected. The oxidative cleavage of -carotene leads to the formation of -cyclocitral and crocetindial and that of zeaxanthin to hydroxy--cyclocitral and crocetindial in nearly stoichiometric amounts. Oxidant is dioxygen as has been demonstrated by high incroporation (86%) of ¹⁸O₂ into -cyclocitral. -Carotene oxygenase is membrane bound, sensitive to sulfhydryl reagents, antioxidants and chelating agents. Iron seems to be an essential part of the enzyme activity. Cofactors necessary for the reaction could not be detected.Abbreviations TLC thin layer-chromatography - PIPES piperazine-N,N-bis-(2-ethanesulfonate) Na - TES 2{[tris-(hydroxymethyl)-methyl]-amino} ethanesulfonic acid Dedicated to Professor G. Drews on occasion of his 60th birthday     

Immunofluorescence and electron microscopic studies of microtubule organization during the cell cycle ofDictyota dichotoma (Phaeophyta,Dictyotales)

Summary Interphase cells ofDictyota dichotoma (Hudson) Lamour. lack cortical microtubules (Mts) but display an impressive network of cytoplasmic microtubules (c-Mts). These are focussed on two opposed perinuclear centriolar sites where centrin or a centrin-homologue is localized. Some of the Mts surround the nucleus, but the majority traverse the cytoplasm as bundles variously directed towards the plasmalemma. In apical cells, and to a lesser extent in the square or slightly elongated meristematic cells, Mts are more or less evenly arranged. In elongated cells they form thick bundles longitudinally traversing the cytoplasm; a pattern maintained in differentiated cells. In early prophase the non-perinuclear Mts disappear but by late prophase a bi-astral arrangement of short Mts is observed. They enter polar nuclear depressions and attach to differentiated regions of the nuclear envelope where polar gaps open. By metaphase the spindle Mts converge on the centrioles at the polar gaps. At anaphase, interzonal Mts are evident and the asters start to reassemble. After telophase disruption of the interzonal Mts, the daughter nuclei approach each other, but move apart again before cytokinesis. The latter movement keeps pace with the development of two interdigitating Mt systems, ensheathing both daughter nuclei. The partition membrane bisects this Mt cage. Between telophase and cytokinesis the centrosomes separate, finally occupying opposed perinuclear sites. New Mts arise at the new centrosomes, some terminating on the consolidating partition membrane. Our data show thatD. dichotoma vegetative cells display a prominent cytoplasmic Mt cytoskeleton, which undergoes continual, but definite, change in organization during the cell cycle.     

Cytogenetic analysis of structural rearrangements in three varieties of common wheat,Triticum aestivum

Summary The winter wheat varieties Starke and Cappelle Desprez and the spring wheat Chinese Spring were analysed for structural chromosome rearrangements that resulted in the formation of multivalents in F₁ hybrids. The analyses were carried out using hybrids involving euploids, monosomic and ditelosomic stocks, and double-monotelodisomic constructs. The study confirmed that Cappelle Desprez differs from Chinese Spring in a reciprocal translocation between chromosomes 5B and 7B (Riley et al. 1967); a translocation involving chromosomes 3B and 3D could not be verified. Furthermore, the analysis showed that Starke differs from Chinese Spring in a reciprocal translocation between chromosomes 7A and 7D. Both translocations have a coefficient of multivalent realisation of about 0.84. Further multivalents in euploid Starke, in euploid and some aneuploid stocks of Cappelle Desprez, and in euploid as well as various types of aneuploid hybrids between all three varieties could nearly all be explained hypothesizing that chromosome 2B of both Starke and Cappelle Desprez is a duplication-deficiency chromosome. In the hypothesis a part of the long arm of 2B is missing and replaced by a duplicated part of the long arm of chromosome 2D. The multivalents of this rearrangement showed an average coefficient of realisation of about 0.09.Sven Ellerström died in December 1985     

Somatic embryogenesis,plant regeneration and somaclonal variation in barley

In vitro culture of immature embryo and young leaf tissues was carried out with five cultivars of barley, Hordeum vulgare. Two cultivars (Albacete and Porthos) responded poorly from both types of explants, while the three others (Dissa, Golden Promise and Ingrid) produced a high frequency of embryogenic callus from these explants (25–60%). For Dissa and Ingrid, young leaf explants were slightly better than immature embryo explants for embryogenic callus induction, while immature embryo cultures of Golden Promise responded better than young leaf explants. Thus, there appears to be a significant genotype × explant interaction in the initiation of embryogenic callus in barley.Some phenotypic variants were detected among the regenerated plants of Golden Promise and Ingrid, most originating by epigenetic changes. Only in one case was the variant phenotype heritable, probably due to a mutation in the chloroplast DNA. Mitotic alteractions were not detected. Consequently, somaclonal variation did not appear to be a very frequent event in plants regenerated from 1- to 6- month-old cultures of barley.     

Solution conformations of proline rings in proteins studied by NMR spectroscopy

Summary Three different conformations of proline rings in a protein in solution, Up, Down and Twist, have been distinguished, and stereospecific assignments of the pyrrolidine -, - and -hydrogens have been made on the basis of ¹H-¹H vicinal coupling constant patterns and intraresidue NOEs. For all three conformations, interhydrogen distances in the pairs -³, ³-³, ²-², ²-², and ³-³ (2.3 Å) are shorter than those in the pairs -², ²-³, ³-², ²-³, and ³-² (2.7–3.0 Å), resulting in stronger NOESY cross peaks. For the Up conformation, the ³-² and ²-³ spin-spin coupling constants are small (<3 Hz), and weak cross peaks are obtained in a short-mixing-time (10 ms) TOCSY spectrum; all other vicinal coupling constants are in the range 5–12 Hz, and result in medium to strong TOCSY cross peaks. For the Down form, the -², ²-³, and ³-² vicinal coupling constants are small, leading to weak TOCSY cross peaks; all other couplings again are in the range 5–12 Hz, and result in medium to strong TOCSY cross peaks. In the case of a Twist conformation, dynamically averaged coupling constants are anticipated. The procedure has been applied to bovine pancreatic trypsin inhibitor and Cucurbita maxima trypsin inhibitor-V, and ring conformations of all prolines in the two proteins have been determined.     

In vitro biosynthesis of the C-glycosidic bond in aloin

Biosynthetic studies with cell-free extracts from Aloe arborescens Mill. demonstrate the transfer of the glucose moiety from UDP-glucose to aloe emodin anthrone, forming the C-glycosidic linkage in the anthracene derivative aloin. The pH-dependence and the specificity of UDP-glucose and aloe emodin anthrone for the biosynthesis of the C-glycosidic bond in aloin are shown.Abbreviations ADP-Glc adenosine-5-diphosphate glucose - AEA aloe emodin anthrone (1,8-dihydroxy-3-(hydroxymethyl)-9(10 H)-anthracenone) - CoASAc acetyl coenzyme A - GDP-Glc guanosine-5-diphosphate glucose - Glc glucose - Glc-1-P glucose-1-phosphate - HPLC high performance liquid chromatography - TLC thin layer chromatography - UDP-Gal uridine-5-diphosphate galactose - UDP-Glc uridine-5-diphosphate glucose     

The impact of domestication on the genetic variability in the orange carrot,cultivated Daucus carota ssp. sativus and the genetic homogeneity of various cultivars

Summary Isozyme analysis of wild and domesticated accessions indicated that domestication of the cultivated carrot Daucus carota ssp. sativus resulted in an insignificant reduction of all genetic variability and genetic distance estimates. Although they are less variable genetically, cultivated forms maintain a high proportion of observed heterozygosity. Relative to the overall genetic variability of the species, samples from four common cultivars Red Cored Chantenay, Scarlet Nantes, Danvers Half Long and A Plus demonstrated a high degree of genetic similarity. This is attributed to the recent development of orange cultivars and the limited gene pool utilized in their development.     

Inheritance of the dwarf plant type in blackgram (Vigna mungo (L.) Hepper)

Summary The inheritance of the dwarf plant type was studied in blackgram (V. mungo (L.) Hepper). Type 9 has erect plant type with normal internode length. The mutant line, EMSD has reduced internode length. The F₁, F₂ and F₃ generations of a cross between Type 9 and EMSD and its reciprocal were studied. The extreme dwarf plant type appeared to be governed by a single recessive gene, dw ₁ dw ₁ with no cytoplasmic effect.Part of Ph.D. Thesis submitted by the first author     

Ultrastructure of freeze-substituted pollen tubes ofLilium longiflorum

Summary In view of the importance of the lily pollen tube as an experimental model and the improvements in ultrastructural detail that can now be attained by the use of rapid freeze fixation and freeze substitution (RF-FS), we have reexamined the ultrastructure of these cells in material prepared by RF-FS. Several previously unreported details have been revealed: (1) the cytoplasm is organized into axial slow and fast lanes, each with a distinct structure; (2) long, straight microtubule (MT) and microfilament (MF) bundles occur in the cytoplasm of the fast lanes and are coaligned with every organelle present; (3) the cortical cytoplasm contains complexes of coaligned MTs, MFs, and endoplasmic reticulum (ER); (4) the cortical ER is arranged in a tight hexagonal pattern and individual elements are closely appressed to the plasma membrane with no space between; (5) mitochondria and ER extend into the extreme apex along the flanks of the pollen tube, and vesicles and ER are packed into an inverted cone-shaped area at the center of the apex; (6) MF bundles in the tip region are fewer, finer, and in random orientation in comparison to those of the fast lanes; (7) the generative cell (GC) cell wall complex contains patches of plasmodesmata; (8) The GC cytoplasm contains groups of spiny vesicles that are closely associated with and seem to be fusing with or pinching off from mitochondria, and (9) the vegetative nucleus (VN) contains internal MT-like structures as well as numerous cytoplasmic MTs associated with its membrane and also located between the VN and GC.Abbrevations CF chemical fixation - ER endoplasmic reticulum - GC generative cell - MF microfilament - MT microtubule - PD plasmodesmata - PM plasma membrane - RF-FS rapid freeze fixation-freeze substitution - VN vegetative nucleus     

Microtubule organization in cultured soybean and black spruce cells: Interphase —mitosis transition and spindle morphology

Summary Microtubule (MT) distribution during the cell cycle, especially spindle organization, has been investigated using immunofluorescence light microscopy in cultured cells of two higher plant species, soybean (angiosperm) and black spruce (gymnosperm). In soybean, the prophase and metaphase spindles were different in morphology and structure. The prophase spindle covering the nucleus was barrel-shaped and MTs extended between poles. The metaphase spindle consisted mainly of short MT bundles on either side of the chromosome mass. During prometaphase, the polarity and shape of the prophase spindle disappeared, suggesting that the metaphase spindle is newly formed in prometaphase and not derived from the prophase spindle. A striking feature of MT organization in black spruce was sharply defined poles during prometaphase and anaphase. They were located close to the cell edge, suggesting that a structure in the cytoplasm or associated with the plasma membrane is responsible for their formation. In black spruce the metaphase spindle was long with pointed poles and MT fir tree structures. In contrast, the metaphase spindle of soybean was short with very broad poles and lacked MT fir trees. These results suggest that MT fir tree structure may not be necessary for a functional spindle.     

SCM2, a tryptophan permease in Saccharomyces cerevisiae, is important for cell growth

SCM2, a novel gene encoding a yeast tryptophan permease, was cloned as a high-copy-number suppressor of cse2-1. The cse2-1 mutation causes cold sensitivity, temperature sensitivity and chromosome missegregation. However, only the cold-sensitive phenotype of cse2-1 cells is suppressed by SCM2 at high copy. SCM2 is located on the left arm of yeast chromosome XV, adjacent to SUP3 and encodes a 65 kDa protein that is highly homologous to known amino acid permeases. Four out of five disrupted scm2 alleles (scm21-4) cause slow growth, whereas one disrupted allele (scm25) is lethal. Cells with both the scm21 and trp1-101 mutations exhibit a synthetic cold-sensitive phenotype and grow much more slowly at the permissive temperature than cells with a single scm21 or trp1-101 mutation. A region of the predicted SCM2 protein is identical to the partial sequence recently reported for the yeast tryptophan permease TAP2, indicating that SCM2 and TAP2 probably encode the same protein.     

Flexibility in the multi-modal courtship of a wolf spider, Schizocosa ocreata

Male Schizocosa ocreata wolf spiders court females with synchronous visual and seismic displays. We tested whether male S. ocreata modify their courtship in relation to light environment, and associated utility of the visual components. Males were generally more active and more likely to perform the major courtship element (jerky tapping) when in the light. One courtship element (arching) was only observed in the light while another (vertical leg-extend) was only observed in the dark. Courtship in the dark retained visual components, suggesting spiders cannot disengage these components of multi-modal display even when superfluous. Once initiated, there was no evidence that performance rate or time spent in each courtship element differed in the light and in the dark.     

A simple protocol for micropropagating diploid and tetraploid watermelon using shoot-tip explants

Shoot-tip explants from 21-day-old aseptically-germinated watermelon seedlings were incubated on solidified MS medium containing test concentrations of benzyladenine (BA) and kinetin (each at 0, 1, 5 or 10 µM), and thidiazuron (TDZ; 0, 0.1, 1 or 5 µM) for 8 weeks. Approximately 1.5x–2.8x more axillary shoots formed at the optimum BA level (1 µM) compared to the best TDZ (0.1 µM) or kinetin (10 µM) concentration. The ability of various diploid and tetraploid genotypes to undergo prolonged axillary shoot proliferation on medium with 1 µM BA was examined. Among the genotypes tested, the number of axillary shoots per explant was greater for Bush Jubilee and Jubilee II than for Minilee, Dixielee, and the tetraploid genotypes. For a majority of the genotypes tested, the number of shoots per explant was low (2.7–4.0) during the first month of culture, peaked (5.3–12.5) at 2 to 3 months, and then declined (3.7–7.7) at 6 months. In contrast, the number of shoots per explant was greatest (11.7) for Bush Jubilee during the first month of culture and declined to 7.7 by the sixth subculture. The percentage of rooted shoots varied from 60% to 100% and the percentage of acclimatized plants ranged from 21% to 96% depending on the genotype and the length of time in culture. Using this procedure, 13,200 finished plants could be produced in 3 months from 250 seedlings.This process is protected by United States patent No. 5,007,198. Those interested in using this technology must secure a license from the University of Florida.     

Structures of asparagine linked oligosaccharides of immunoglobulins (IgY) isolated from egg-yolk of Japanese quail

Structures of the Asn linked oligosaccharides of quail egg-yolk immunoglobulin (IgY) were determined in this study. Asn linked oligosaccharides were cleaved from IgY by hydrazinolysis and labelled withp-aminobenzoic acid ethyl ester (ABEE) afterN-acetylation. The ABEE labelled oligosaccharides were then fractionated by a combination of Concanavalin A-agarose column chromatography and anion exchange, normal phase and reversed phase HPLC before their structures were determined by sequential exoglycosidase digestion, methylation analysis, HPLC, and 500 MHz¹H-NMR spectroscopy. Quail IgY contained only neutral oligosaccharides of the following categories: the glucosylated oligomannose type (0.6%, Glc1-3Glc1-3Man₉GlcNAc₂; 35.6%, Glc1-3Man_7–9GlcNAc₂). oligomannose type (15.0%, with the structure Man_5–9GlcNAc₂) and biantennary complex type with core structures of-Man1-3(-Man1-6)Man1-4GlcNAc1-4GlcNAc (9.9%),-Man1-3(GlcNAc1-4)(-Man1-6)Man1-4GlcNAc1-4GlcNAc (25.1%) and-Man1-3(GlcNAc1-4)(-Man1-6)Man1-4GlcNAc1-4(Fuc1-6)GlcNAc (11.4%). Although never found in mammalian proteins, glucosylated oligosaccharides (Glc₁Man_7–9GlcNAc₂) have been located previously in hen IgY.Abbreviations IgG, IgM, IgA, IgY immunoglobulin G, M, A and Y, respectively - ABEE p-aminobenzoic acid ethyl ester