Dynamics of Responses in Compatible Potato - Potato virus Y Interaction Are Modulated by Salicylic Acid

To investigate the dynamics of the potato – Potato virus Y (PVY) compatible interaction in relation to salicylic acid - controlled pathways we performed experiments using non-transgenic potato cv. Désirée, transgenic NahG-Désirée, cv. Igor and PVYNTN, the most aggressive strain of PVY. The importance of salicylic acid in viral multiplication and symptom development was confirmed by pronounced symptom development in NahG-Désirée, depleted in salicylic acid, and reversion of the effect after spraying with 2,6-dichloroisonicotinic acid (a salicylic acid - analogue). We have employed quantitative PCR for monitoring virus multiplication, as well as plant responses through expression of selected marker genes of photosynthetic activity, carbohydrate metabolism and the defence response. Viral multiplication was the slowest in inoculated potato of cv. Désirée, the only asymptomatic genotype in the study. The intensity of defence-related gene expression was much stronger in both sensitive genotypes (NahG-Désirée and cv. Igor) at the site of inoculation than in asymptomatic plants (cv. Désirée). Photosynthesis and carbohydrate metabolism gene expression differed between the symptomatic and asymptomatic phenotypes. The differential gene expression pattern of the two sensitive genotypes indicates that the outcome of the interaction does not rely simply on one regulatory component, but similar phenotypical features can result from distinct responses at the molecular level

Molecular analysis of desiccation tolerance in barley embryos and in the resurrection plant Craterostigma plantagineum

Two experimental systems, developing barley embryos and the desiccation-tolerant plant Craterostigma plantagineum, have been used to isolate cDNA clones specifically expressed in dehydrated tissues. Sequence analysis revealed that most of the isolated cDNA clones show homologies to previously reported genes. Most of the desiccation-induced genes in Craterostigma encode polypeptides with substantial homologies to proteins expressed during late embryogenesis in many higher plants. The expression of these genes is induced by abscisic acid treatment in leaves and in undifferentiated callus tissue. Subcellular localization of the corresponding proteins shows that most are cytoplasmic and that 3 dehydration-induced proteins are localized in the chloroplast. In developing barley embryos, some of the cDNA clones are related to genes encoding enzymes involved in sugar metabolism. One of these clones shows high homology to the animal aldose reductases involved in the synthesis of the osmolyte sorbitol. The protein encoded by this clone has been over-expressed in Escherichia coli and the purified protein shows aldose reductase activity.Analyse moléculaire de la tolérance à la dessiccation d'embryons d'orge et de la « plante à résurrection » Craterostigma plantagineum. Deux systèmes expérimentaux, à savoir les embryons d'orge et la « plante à résurrection » Craterostigma plantagineum, ont été utilisés pour isoler des clones d'ADNc exprimés de manière spécifique dans les tissus déshydratés. L'analyse de séquence de ces clones révèle, dans la plupart des cas, une homologie avec des gènes déjà connus. Chez Craterostigma plantagineum, la plupart des gènes induits par la dessiccation codent pour des polypeptides similaires aux protéines exprimées durant l'embryogenèse tardive de plusieurs plantes supérieures. L'expression de ces gènes est induite par des traitements à l'ABA sur des feuilles ou des cals. Les protéines induites par la déshydratation sont pour la plupart localisées dans le cytoplasme mais 3 d'entre elles sont chloroplastiques. Dans les embryons d'orge en développement, certains de ces clones d'ADNc présentent une homologie avec des gènes codant pour des enzymes impliquées dans le métabolisme des glucides. Un de ces clones montre une forte homologie avec le gène de l'aldose réductase animale qui intervient dans la synthèse du sorbitol. La protéine codée par ce clone a été surexprimée chez E coli. Après purification, cette protéine possède une activité aldose réductase

Sheep-passaged bovine spongiform encephalopathy agent exhibits altered pathobiological properties in bovine-PrP transgenic mice.

Sheep can be experimentally infected with bovine spongiform encephalopathy (BSE), and the ensuing disease is similar to scrapie in terms of pathogenesis and clinical signs. BSE infection in sheep is an animal and human health concern. In this study, the transmission in BoPrP-Tg110 mice of prions from BSE-infected sheep was examined and compared to the transmission of original cattle BSE in cattle and sheep scrapie prions. Our results indicate no transmission barrier for sheep BSE prions to infect BoPrP-Tg110 mice, but the course of the disease is accelerated compared to the effects of the original BSE isolate. The shortened incubation period of sheep BSE in the model was conserved in subsequent passage in BoPrP-Tg110 mice, indicating that it is not related to infectious titer differences. Biochemical signature, lesion profile, and PrP(Sc) deposition pattern of both cattle and sheep BSE were similar. In contrast, all three sheep scrapie isolates tested showed an evident transmission barrier and further adaptation in subsequent passage. Taken together, those data indicate that BSE agent can be altered by crossing a species barrier, raising concerns about the virulence of this new prion towards other species, including humans. The BoPrP-Tg110 mouse bioassay should be considered as a valuable tool for discriminating scrapie and BSE in sheep