Genomic in situ hybridization in Brassica amphidiploids and interspecific hybrids

Genomic in situ hybridization (GISH) methods were used to detect different genome components within Brassica amphidiploid species and to identify donor chromatin in hybrids between Brassica napus and Raphanus sativus. In Brassica juncea and Brassica carinata the respective diploid donor genomes could be reliably distinguished by GISH, as could all R-genome chromosomes in the intergeneric hybrids. The A- and C-genome components in B. napus could not be clearly distinguished from one another using GISH, confirming the considerable homoeology between these genomes. GISH methods will be extremely beneficial for monitoring chromatin transfer and introgression in interspecific Brassica hybrids. Received: 20 May 1997 / Accepted: 28 July 1997     

HYBRIDIZATION STUDIES ON THE HOST RACES OF EUROSTA SOLIDAGINIS: IMPLICATIONS FOR SYMPATRIC SPECIATION

We studied the inheritance of survival ability in host-associated populations of the tephritid fly, Eurosta solidaginis, to test predictions of sympatric speciation models. Eurosta solidaginis induces galls on two species of goldenrod, Solidago altissima and S. gigantea. The host-associated populations have been hypothesized to be host races that originated in sympatry (Craig et al. 1993). We found evidence for disruptive selection for host use, which is a critical assumption of sympatric speciation models. Each host race had higher survival rates on their host plant than on the alternative host. F₁ and backcross hybrids also had lower survival rates than the pure host-race flies on their host plant. Since assortative mating occurs due to host-plant preference (Craig et al. 1993) this would select for divergence in host preference. Low hybrid survival could have been due to strong genetic incompatibilities of the populations or due to host adaptation by each population. Strong genetic incompatibilities would result in poor survival on all host plants, while host adaptation could result in low overall survival with high hybrid survival on some host plants with particularly “benign” environments. High survival of F₁, F₂, and backcross hybrids on some plant genotypes in some years supported the host adaptation hypothesis. F₁ flies mated and oviposited normally and produced viable F₂ and backcross hybrids indicating gene flow is possible between the host races. A few flies developed and emerged on the alternative host plant. This demonstrates that genes necessary to utilize the alternative host exist in both host races. This could have facilitated the origin of one of the populations via a host shift from the ancestral host. The inheritance of survival ability appears to be an autosomal trait. We did not find evidence that survival ability was maternally influenced or sex linked.     

Resin acids of Pinus resinosa needles

The principal resin acids in the needles of Pinus resinosa are the labdane diterpenes, the new 8,13-epoxy-14-labden-19-oic acid (epimanoyl oxide acid), 8,13β-epoxy-14-labden-19-oic acid (manoyl oxide acid), 8(17),E-12,14-labdatrien-19-oic acid (communic acid) and 15-oxo-8(17)-labden-19-oic acid (imbricataloic acid). A survey of needles from representative populations of P. resinosa showed a limited variability in resin acid composition consistent with the uniformity of other traits. The composition of needle resin acids for putative P. nigra x resinosa hybrids strongly suggests the improbability of P. resinosa as the pollen parent.     

Evidence of mitochondrial DNA clones of Siberian sturgeon, Acipenser baerii, within Russian sturgeon, Acipenser gueldenstaedtii, caught in the River Volga

Eleven of 34 sturgeons caught in the River Volga classified morphologically as Acipenser gueldenstaedtii were identified as Acipenser baerii from sequence analysis of the mitochondrial cytochrome- b gene. The Caspian Sea and its tributaries including the Volga are not native habitats of A. baerii . No A. baerii haplotype was observed in A. gueldenstaedtii from the Sea of Azov or the South Caspian Sea. Genetic contamination of A. gueldenstaedtii with A. baerii or A. baerii hybrids has occurred in the Volga. Crosses and backcrosses of these specimens with native A. gueldenstaedtii resulted in the loss of the morphological diagnostic A. baerii features. These findings are of special concern for conservation and management programmes, as well as for specimen identification for caviar trading control.     

Anaerobically induced production of hybrid monokaryons by heterokaryons of Candida albicans

Summary During aerobic replication, balanced heterokaryons (hets) of Candida albicans produced by fusing protoplasts of complementing auxotrophic strains characteristically segregate low frequencies of prototrophic monokaryons bearing hybrid nuclei formed either through karyogamy or unidirectional internuclear genetic transfers within het cells. Anaerobic growth causes exponential inactivation of hets and induces their production of hybrid monokaryons. Both responses are functions of heterokaryosis as such and not the genetic backgrounds of hets. Evidence is presented that (i) the nuclei of anaerobically generated hybrids arise through induction in hets of karyogamy not internuclear genetic transfers and that (ii) the events underlying that induction are different from those responsible for inactivation of the cells.     

Structural analysis of prokaryotic and eukaryotic 5S rRNAs by RNase H

The availabilities of single-stranded 5S rRNA regions c, d and d' for base pairing interactions were analyzed by using synthetic DNA oligomers. Hybrid formation was detected by the endonucleolytical mode of the RNA-DNA specific action of RNase H. Provided that the hybrid interaction involved 6 successive base pairs, 5S rRNA loop c nucleotides 42-47 displayed accessibility in Escherichia coli, Bacillus stearothermophilus and Thermus thermophilus 5S rRNAs as well as in eukaryotic 5S rRNAs from Saccharomyces carlsbergensis, Rattus rattus and Equisetum arvense. Investigating eubacterial 5S rRNA regions d and d' (nucleotides 71-76 and 99-105, respectively), susceptibility was observed in E. coli 5S rRNA which, however, decreases in B. stearothermophilus and even more so in T. thermophilus 5S rRNA. For additional evaluation of the data obtained by RNase H cleavage, association constants of the hexanucleotides were determined by equilibrium dialysis at 4 degrees C for B. stearothermophilus 5S rRNA. The results obtained reveal that nucleotides 36-41 of B. stearothermophilus 5S rRNA are inaccessible for Watson-Crick interaction, which suggests that this part of loop c is in a structurally constrained configuration, or buried in the tertiary structure or involved in tertiary interactions.     

Chromosome evolution within theOrnithogalum tenuifolium complex (Hyacinthaceae), with special emphasis on the evolution of bimodal karyotypes

Hypotheses on the evolution of the karyotypes of 8 chromosome races (2n = 4, 6, 8, 10, 12, 16-two forms, 26) within theOrnithogalum tenuifolium complex are discussed. Four of the karyotypes are strictly bimodal: 2n = 8 (6 long and two short chromosomes), 2n = 10 (6 long and 4 short chromosomes), 2n = 12 (6 long and 6 short chromosomes) and 2n = 16 (12 long and 4 short chromosomes). The hypotheses are tested by means of measurements of nuclear DNA content, studies of meiosis and pollen fertility of hybrids, and comparisons of karyotype morphology. The results indicate that the E. African 2n = 12 chromosome race is the most primitive and has given rise to the other chromosome races. The 2n = 6 race is found to have a significantly higher fitness than the 2n = 12 race.     

Zur funktionellen Bedeutung der osmiophilen Granula in Herzorganen niederer Vertebraten

Zusammenfassung Elektronenmikroskopische Untersuchungen am Herzen niederer Vertebraten (Frosch, Forelle, Goldfisch) und am Lymphherzen des Frosches zeigen, daß osmiophile intrazelluläre Granula (800–1300 Å) als Ausdruck sekretorischer Funktionen der Herzmuskelzellen bei verschiedenen poikilothermen Vertebraten vorkommen. — Innerhalb der Granulaansammlungen in Muskelzellen des Froschventrikels werden neben Dictyosomen, Vesikeln und Multivesikulärkörpern besondere Multivesikulärkörper mit Dichtekern gefunden. Übereinstimmende vesikuläre Substruktur dieses Dichtekerns und der spezifischen Granula sowie der Übergangsformen ergeben eine morphogenetische Reihe: Golgiapparat Multivesikulärkörper Multivesikulärkörper mit Dichtekern spezifisches Granulum. — Zwischen den Muskelzellen des Rana-Herzens wird wie bei Cyclostomen ein Zelltyp mit osmiophilen Granula gefunden, die in Größe und Struktur auch den Granula in den terminalen adrenergen Nervenfasern des Froschherzens entsprechen.Vieltägige Isolation des Froschherzens unter physiologischen Bedingungen sowie Inkubierung oder längere Behandlung isolierter Forschherzen mit Reserpin führt zum Abbau der spezifischen Granula. Oxypertin und Acetylcholin haben nur geringen Einfluß auf deren Größe, Struktur und Zahl. L-Dopa und Adrenalin wirken einer isolationsbedingten Reduktion der Granula entgegen. — Fluoreszenzmikroskopisch kann am Rana-Herzen intramuskulär eine auf Catecholamine hindeutende punktartige Gelbgrün-Fluoreszenz nachgewiesen werden. Nach Rückgang des Granulagehaltes durch Reserpin zeigt das isolierte Froschherz eine Sensibilisierung für Acetylcholin und Adrenalin.Es ist wahrscheinlich, daß die spezifischen Granula in den Herzorganen der untersuchten Arten (wie die entsprechenden Strukturen im Cyclostomenherzen) Catecholamine speichern, die für eine gleichbleibende Erregbarkeit der Muskelfasern von Bedeutung sein könnten.

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Function of the osmiophilic granules in the heart-organs of lower vertebratesA comparative electron microscopic and pharmacological study on the isolated heart of frog and other poikilothermic vertebrates

Summary Electron microscopic studies of the hearts of lower vertebrates (frog, trout, goldfish) and of the lymph-heart (frog) show that osmiophilic intracellular granules probably are related to secretory functions of cardiac muscle cells in poikilothermic vertebrates. — Beside dictyosomes, vesicles, and usual multivesicular bodies, a special type of multivesicular body with a dense core is found among the granules in the muscle cells of the frog's ventricle. The vesicular substructure of this dense core, and the specific granules as well as the intermediate forms suggest the following morphogenetic process: Golgisystem multivesicular body multivesicular body with a dense core specific granule. Between the muscle cells of the heart of Rana, as well as with Cyclostomata, a cell type with osmiophilic granules can be found corresponding in size and structure to the adrenergic terminals of the frog's heart.Many days' isolation of the frog's heart under physiological conditions, as well as incubation, or longer treatment of isolated hearts of frogs with reserpine leads to the dissolution of the specific granules. Oxypertin and acetylcholine have only little influence on the size, structure, and number of granules. L-Dopa and adrenalin appose a reduction of granules caused by isolation. Fluorescence microscopic results show a point-like yellow-green fluorescence in the heart of Rana, pointing to an accumulation of catecholamines intramuscularly.— After reduction of the content of granules by reserpine, the isolated frog's heart shows a higher sensitivity to acetylcholine and adrenalin.It is, therefore, probable that the specific granules store catecholamines in the heart organs of the investigated species in the same way as corresponding structures do in the hearts of Cyclostomata. These catecholamines are possibly important for a continual irritability of the cardiac muscle fibres in poikilothermic vertebrates.

Frau A. Beyerle-v. Wehren sei für ihre wertvolle technische Unterstützung gedankt.     

Somatic hybridization in higher plants

Summary Somatic hybridization in higher plants has come into focus since methods have been established for protoplast fusion and uptake of foreign DNA and organelles by protoplasts. Polyethylene glycol (PEG) was an effective agent for inducing fusion. Treatment of protoplasts with PEG resulted in 5 to 30% heterospecific fusion products. Protoplasts of different species, genera and even families were compatible when fused. A number of protoplast combinations (soybean + corn, soybean + pea, soybean + tobacco, carrot + barley, etc.) provided fusion products which underwent cell division and callus formation. Fusion products initially were heterokaryocytes. In dividing heterokaryocytes, random distribution of mitotic nuclei was observed to be accompanied by multiple wall formation and to result in chimeral callus. Juxtaposition of mitotic nuclei suggested nuclear fusion and hybrid formation. Fusion of heterospecific interphase nuclei was demonstrated in soybean + pea and carrot + barley heterokaryons. Provided parental protoplasts carry suitable markers, the fusion products can be recognized. For the isolation and cloning of hybrid cells, fusion experiments must be supplemented with a selective system. Complementation of two nonallelic genes that prevent or inhibit growth under special culture conditions appears as the principle on which to base the selection of somatic hybrids. As protoplasts of some species have been induced to regenerate entire plants, the development of hybrid plants from protoplast fusion products is feasible and has already been demonstrated for tobacco. Presented in the formal symposium on Somatic Cell Genetics at the 27th Annual Meeting of the Tissue Culture Association, Philadelphia, Pennsylvania, June 7–10, 1976.     

Sorghum-sudan green manure; Its effect on nursery stock

Summary The use of sorghum-sudan green manure has recently attained popularity among nurserymen because of the assumption that toxic excretions of these hybrids control root-rot fungi. Greenhouse trials of 2-year duration have revealed that green manure of sorghum-sudan inflicts severe damage of tree seedlings, largely by eradication of mycorrhiza-forming fungi. Early plowing under of green manure, periodic watering, and late fall seeding of nursery crop may alleviate phytotoxicity of the sorghum-sudan residues, but the biocidic properties of these plants defeat the primary purpose of using green manure in contemporary nurseries, namely the biodegradation of toxic compounds.Research supported by the College of Agricultural and Life Sciences, University of Wisconsin, Madison, and the Wisconsin Department of Natural Resources.