Analysis of hybrids of durum wheat with Thinopyrum junceiforme using RAPD markers

 The objective of this study was to detect the presence of alien chromatin in intergeneric hybrids of durum wheat (Triticum turgidum, 2n=4x=28; AABB genomes) with the perennial grass Thinopyrum junceiforme (2n=4x=28; J₁J₁J₂J₂) using RAPD markers. The first step was to identify amplification of species-specific DNA markers in the parental grass species and durum wheat cultivars. Initially, the genomic DNA of five grass species (Thinopyrum junceiforme, Th. bessarabicum, Lophopyrum elongatum, Leymus karataviensis and Elytrigia pycnantha) and selected durum cultivars (‘Langdon’, ‘Durox’, ‘Lloyd’, ‘Monroe’, and ‘Medora’) was screened with 40 oligonucleotide primers (nano-mers). Three oligonucleotides that amplified DNA fragments specific to a grass species or to a durum cultivar were identified. Primer PR21 amplified DNA fragments specific to each of the five durum cultivars, and primers PR22 and PR23 amplified fragments specific to each of the grass species. Intergeneric hybrids between the durum cultivars ‘Langdon’, ‘Lloyd’ and ‘Durox’ and Th. junceiforme, and their backcross (BC) progeny were screened with all 40 primers. Six primers amplified parent-specific DNA fragments in the F₁ hybrids and their BC₁ progeny. Three primers, PR22, PR23 and PR41, that amplified Th. junceiforme DNA fragments in both F₁ and BC₁ were further analyzed. The presence of an amplified 1.7-kb Th. junceiforme DNA fragment in the F₁ hybrids and BC₁ progeny was confirmed using Southern analysis by hybridization with both Th. junceiforme genomic DNA and Th. junceiforme DNA amplified with primer PR41. With the exception of line BC₁F₂ no. 5, five selfed progeny of BC₁ and a BC₂ of line 3 (BC₁F₂ no. 3בLloyd’) from a cross of ‘Lloyd’×Th. junceiforme showed the presence of the 1.7-kb DNA fragment. All selfed BC₁ and BC₂ lines retained the 600-bp fragment that was confirmed after hybridization with Th. junceiforme DNA amplified with primer PR22. Other experiments using RFLP markers also showed the presence of up to seven Th. junceiforme DNA fragments in the F₁ hybrids and their BC progeny after hybridization with Th. junceiforme DNA amplified with primer PR41. These studies show the usefulness of molecular markers in detecting alien chromatin/DNA fragments in intergeneric hybrids with durum wheat. Received: 21 November 1996 / Accepted: 21 March 1997     

Laboratory studies of egg development and diapause in Isoperla obscura (Plecoptera) from a mountain stream in Norway

SUMMARY 1. A laboratory study of egg development of the stonefly Isoperla obscura (Zetterstedt) collected from the stream Flybekken (southern Norway, 61°25'N, 8°48'E, 1373 m a.s.l.) showed a short diapause followed by a prolonged period of postdiapause quiescence.
2. Diapause occurred over a wide range of temperatures (−20°C to +8°C), but 0–1°C was the most favourable for fast diapause development and successful hatching. Diapause development required temperatures below 12°C, but sub-zero diapause temperatures increased mortality during the postdiapause phase, as well as reducing hatching success.
3. The threshold for initiation of postdiapausal development was about 1–2°C. Development rate increased and variation in development time decreased at higher water temperatures. These may be important characteristics to ensure seasonal and geographical synchrony of development in individual populations. Low postdiapausal temperatures were unfavourable, despite a subsequent increase in water temperature. No response to postdiapausal photoperiod was detected.
4. The results agreed well with conditions noted in the natural environment, and with the abundance of this species at high altitudes and latitudes in Fennoscandia. Nevertheless, Isoperla obscura also occurs in streams in the maritime parts of western Norway. The results of the present study suggest that egg development in these populations will prove to be different.     

Demonstration of Voltage-Dependent and TTX-Sensitive Na+-Channels in Human Melanocytes

The electrophysiological properties of cultured human melanocytes were investigated using the whole-cell configuration of the patch-clamp technique. Depolarizations to membrane potentials more positive than -30 mV resulted in the rapid development (<1 ms to peak) of an inward current. The maximum peak current was observed at +10 mV and reached an average amplitude of about 270 pA. During the depolarizations, the current inactivated with a time constant of about 2 ms. The current was abolished by the addition of 0.3 μM tetrodotoxin, a blocker of voltage-gated Na⁺-channels, and disappeared when Na⁺ was omitted from the extracellular medium. In addition, the melanocytes contain at least two types of outward K⁺-current. The first type, observed in every cell, was highly sensitive (K_i 1 mM) to the K⁺-channel blocker TEA, required depolarizations beyond zero to be activated and did not inactivate. The second type was less regularly observed (10% of the cells). This current activated at more negative voltages (–20 mV), was resistant to TEA (20 mM) but was blocked by 2 mM 4-aminopyridine and inactivated rapidly during depolarizations. We conclude that human melanocytes are equipped with voltage-dependent Na⁺-channels, a delayed rectifying K⁺-current and a K⁺-current similar to the A-current in neurones.     

Ca2+ and peroxidase derived from cultured peanut cells

A 5% increase of Ca²⁺ content of the incubation medium for cultured peanut ( Arachis hypogaea L.) cells caused a rise of peroxidase (EC 1.11.1.7) activity in the medium, which could be abolished by the addition of the chelator EGTA [eth-yleneglycol-bis-(β-aminoethyl ether)-N,N,N',N'-tetraacetic acid]. However, the determination of in vivo peroxidase synthesis in these cells showed that Ca²⁺ had a direct effect on the biosynthesis rather than on transport alone. This concept was re-enforced by the lack of effect by the ionophore A23187 on the transport. The Ca²⁺ content was 2 and 5 mol (mol protein⁻¹) for the cationic and anionic peanut peroxidase, respectively. The latter is different from the value reported for the anionic peroxidase from horseradish.     

Some aspects of life strategies of Early Palaeozoic rugose corals

Examination of some well-preserved specimens of Silurian rugose corals from Gotland reveals that the following categories of life strategies can be distinguished: ambitopic, liberosessile, fixosessile, rhizosessile and possibly limited vagile. Most solitary rugose corals appear to have been liberosessile and are characterized by initial attachment to a small sediment grain but subsequently becoming recumbent on a soft substrate. Detailed studies of Phaulactis angelini, Holophragma calceoloides, Laccophyllum lindstroemi, Rhegmaphyllum conulus and Rhabdocyclus ocksaroensis n. sp., and comparison with earlier described species, provide some new aspects on different life strategies for solitary corals.     

The use of RAPD analysis to classify Triticum accessions

 Crop germplasm collections contain a considerable percentage of misclassified accessions which may affect the use of germplasm for agricultural crop improvement. The objective of this study was to determine if random amplified polymorphic DNA (RAPD) analysis could be used to reclassify misclassified Triticum accessions. Twelve accessions suspected to be misclassified, based on morphological characters, as either macha or vavilovii wheat were studied using RAPD and cytological analyses. In the RAPD analysis, a dendrogram, based on Jaccard genetic similarity coefficients, grouped 5 dicoccum-like, 1 timopheevii-like, and 6 monococcum-like accessions with Triticum dicoccum, T. timopheevii, and T. monococcum accessions, respectively. These results were confirmed by the cytological analysis. A RAPD marker specific to the D genome was also detected. This study suggests that RAPD analysis can be used to classify germplasm and to distinguish some species in Triticum. Received: 12 June 1998 / Accepted: 18 August 1998     

Six polymorphic microsatellite loci in the Natterjack toad,Bufo calamita

The Natterjack toad, Bufo calamita, is a locally endangered anuran endemic to Europe. It has been used as a model organism in several ecological studies. When studying the genetic structure of marginalized populations of the species, there was a need to involve more loci in the study than those previously published. Here we present the development of six polymorphic microsatellite loci in the Natterjack. The loci will be used for studying population genetic structure and gene flow between populations.