The differentiation of Phytophthora species that are pathogenic on potatoes by an asymmetric PCR combined with single-strand conformation polymorphism analysis

The goal of this study was to develop a polymerase chain reaction (PCR) capable of differentiating Phytophthora species that are pathogenic on potatoes using a single primer pair. To achieve this objective, primers were derived from conserved regions flanking variable sequences in the internal transcribed spacer 1 (ITS1) of Phytophthora species. One primer pair produced a 140 bp product from P. infestans , P. erythroseptica and P. nicotianae . The PCR products were purified and used in an asymmetric PCR (A-PCR) protocol to generate single-strand DNA (ssDNA). The ssDNA of the Phytophthora potato pathogens reproducibly migrated in non-denaturing polyacrylamide gels in a species-specific manner.     

Effect of high-level oxygen exposure on the peroxidase activity and the neuromelanin-like pigment content of the nerve net in the earthworm, Lumbricus terrestris

Histochemical examination of 1-μm tissue sections from the dorsal nerve plexus of the earthworm, Lumbricus terrestris, reveals multiple brown intraneuronal granules. These granules contain material morphologically and histochemically consistent with neuromelanin. When viewed with transmission electron microscopy, these were seen as single membrane-enclosed biphasic granules with diameters of 370–730 nm. Exposure of L. terrestris to high-level environmental oxygen resulted in an increase in the number of neuromelanin-like pigment granules within the neurons of the circular muscle layer. As measured by ortho-phenylenediamine hydrochloride, the endogenous peroxidase activity of extracts from worms incubated in high-level environmental oxygen was 51% more than controls. The endogenous peroxidase activity was localized in situ with 3,3-diaminobenzidine (DAB) and was found to increase in and around the neuromelanin-like pigment-containing neurons within the circular muscle layer. These studies suggest that the nerve net of L. terrestris may serve as a model to study the role of neuromelanin production in oxidative stress and its relationship to endogenous peroxidases.     

The use of an oligonucleotide that hybridizes to DNA sequences interspersed in the genome of members of the genusPhytophthora as an adjunct to morphological criteria in species identification

An oligonucleotide (primer), designed from a conserved region of the multi-allelicb locus of the basidiomycete fungusUstilago maydis, generated reproducible PCR fingerprints inPhytophthora species. The primer hybridized in a species-specific manner to nucleotide sequences interspersed in the genome of the closely related members ofPhytophthora taxonomic group IV. We recommend the use of this PCR procedure as an alternative method for resolving the close taxonomic affinity of some members of the genusPhytophthora.