Molecular Characterization of a Barley Gene Induced by Cold Treatment

A cDNA library was made from low positive temperature (6 ?C/2?C) grown barley shoot meristems. Several genes which are differentiallyexpressed, as measured by mRNA abundance, were selected fromthe library using a differential screen. This paper reportsan analysis of in vivo expression in several cultivars, theDNA sequence, copy number and chromosomal location of one gene(BLT14). In addition, genomic restriction fragment length polymorphismfor this gene in the 10 most widely UK-grown spring and 9 mostwidely UK-grown winter barley cultivars is analysed. Key words: Hordeum vulgare, low temperature, RFLP, differential expression, cDNA sequence     

Effects of Inhibitory Concentrations of 3-Indolylacetic Acid and 3-Indolylacetonitrile on Cell Division and Tissue 2

Inhibitory concentrations of 3-indolylacetonitrile (IAN) cause,in cultured excised tomato roots, a marked decrease in the rateof cell division at the apical meristem but only a slight reductionin the lengths of mature exodermal and cortical cells. The reducedrate of cell division is associated with a decrease in the.number of meristematic cells at the root apex. By contrast,3-indolylacetic acid (IAA) causes marked reduction in the lengthsof mature cortical cells but does not markedly reduce cell-divisionrate at the apical meristem. Various lines of evidence indicate that both IAA and IAN causea relative increase in the number of longitudinal and a decreasein the number of transverse division walls in the meristematiczone of the root apex. Partial inhibition of the linear growth of excised tomato rootsby IAA and IAN is accompanied by increases in root and stelardiameters. These increases result from radial enlargement ofthe cortical cells and increase in the number of stelar cellsin the transverse section. The enlarged steles contain an increasednumber of lignified xylem elements, but only with the most inhibitoryconcentration of IAN (10^–4g./ml.) is there evidence ofthe development of secondary xylem. Both auxins increase significantlythe xylem vessel unit length.     

The effect of food availability, female culture-density and photoperiod on ephippia production in Daphnia magna Straus (Crustacea: Cladocera)

SUMMARY. A method is described whereby ephippia (sexual eggs plus protective membranes) are experimentally induced at low food levels (≤ 0.05 mg spinach D. magna ^-1), high female culture-densities (≤ 0.4 D. magna ml^-1) and in short-day photoperiods (L:D < 12:12, 12°C). The density-dependent ephippial response was related to an increased encounter rate between females at the higher densities. External metabolites had no significant effect on ephippia production. Ephippia were formed in the second generation after exposure to short day-lengths. Five clones from the same population exhibited genetic variation in their critical photoperiods for induction of sexual reproduction (≥= 10% ephippia). There was evidence of a genetic difference in photoresponse between two populations of D. magna. The evolution of timing mechanisms for ephippia production are discussed in relation to the predictability of environmental change.     

Evidence for long-distance dispersal in a sedentary passerine, Gymnorhina tibicen (Artamidae)

Australian magpies (Gymnorhina tibicen) are group-living birds found across much of mainland Australia. Adults commonly remain in a breeding territory until death. Young of the year either remain on the natal (birth) site or are forced by their parents to disperse. Observational studies in south-eastern Australia suggest that most dispersing juveniles settle within 7 km of their natal territory. Therefore, despite potential for considerable gene flow (via flight), social organization predisposes magpies towards local population structuring. In this study, we measured genetic variation at both nuclear (allozyme) and mitochondrial loci and found evidence of substantial gene flow over very large distances (up to 1599 km). Thus, some juvenile magpies may disperse much greater distances than was previously thought. For mtDNA, geographic and genetic distance were strongly correlated, consistent with a pattern of isolation by distance. Therefore, although female gene flow is substantial it is apparently geographically restricted over large distances, in approximately a stepping-stone fashion. We conclude that a strong relationship between gene flow and geographic distance can develop even over large distances if populations have experienced no major historical disturbances to gene flow.     

Noninvasive methodology for the sampling and extraction of DNA from free‐ranging Atlantic spotted dolphins (Stenella frontalis)

Genetic sampling and molecular investigations are important parts of studying wild populations. However, collecting tissues from free‐ranging animals can be difficult or impractical. This study develops a sampling and extraction protocol for template DNA from faecal material collected in a marine environment from small cetaceans. DNA was extracted from faecal material of free‐ranging Atlantic spotted dolphins (Stenella frontalis) and subsequently tested for its suitability in molecular investigations by amplifying both mitochondrial and nuclear DNA. The resulting mitochondrial sequences were found to closely match known S. frontalis haplotypes. Three microsatellite loci were amplified and fall within the expected size range for cetaceans. Mother and calf families previously assigned by observation were genetically confirmed using both mitochondrial haplotype and allele sharing between the mother and offspring. The protocol effectively collects and extracts dolphin DNA from faecal samples and enables species identification as well as confirmation of genetic relatedness and should be considered as a noninvasive alternative to current protocols.     

The use of protein A-sandwich ELISA as a means for quantifying serological relationships between members of the tobamovirus group

Indirect protein A sandwich ELISA (PAS-ELISA) was used to determine the serological relationship between eight tobamoviruses with antisera to 26 viruses and virus strains within the group. Very distant relationships were determined by trapping virus with heterologous antiserum and detecting it with homologous antiserum, while near and close relationships were differentiated by using heterologous antiserum each time. The results were esssentially consistent with previously recorded relationships determined by tube precipitin and other serological tests. Since PAS-ELISA requires much less antiserum than many conventional tests and does not require the purification of IgG or virus, it may offer many advantages in the detection of serological relationships.