Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
1999
Authors
Heleen A. de Wit M. Kotowski Jan MulderAbstract
No abstract has been registered
Authors
Bent C. BraskerudAbstract
No abstract has been registered
Authors
Carl Gunnar FossdalAbstract
Plants are exposed to a great number of microorganisms under natural conditions. Pathogenic fungi and oomycetes are the main factors contributing to plant diseases, thus further understanding of plant-pathogen interactions may provide information leading to new strategies for reducing the damage caused by these pathogens on economically important trees and crops. Active plant-responses to microorganisms differ with respect to the degree of responses and with respect to the outcome of the interaction. In response to pathogens, active plant-defenses can be induced. Both local and systemic plant defense-response may be induced by pathogens. This thesis present indications of both local and systemic host responses at the molecular and cellular levels, using the conifer Norway spruce as a model host to study plan-pathogen interactions. Norway spruce seedlings were infected separately with the pathogenic fungi Heterobasidion annosum and Ceratocystis polonica, the pathogenic oomycete Pythium dimorphum and the ectomycorrhizal fungus Laccaria bicolor, to study the local and systemic effects of the infections at the cellular and molecular level. Increased levels of lignification was seen within 2 to 4 days in response to the pathogens, and indications of cytoplasmic translocations were also observed as a response to hyphae invading the root. Initially, a defense related plant peroxidase cDNA SPI2 (spruce pathogen induced 2) from Norway spruce roots was isolated and sequenced and found to encode a predicted 34kD SPI2 protein. The 34kD SPI2 protein was detected both in the root and shoot of Norway spruce seedlings, and accumulated as a local response to infection with the pathogenic oomycete Pythium dimorphum. In addition, two 38kD and 39kD SPI2 related proteins were detected in roots only after infection. Interestingly, increase levels of the 39kD SPI2 related protein was also detected in shoots of infected seedlings as a systemic response to infection. The putative plant defensin SPI1 (spruce pathogen induced 1) from Norway spruce has been proposed a role in the defense against pathogenic fungi and oomycetes. Here the predicted 5kD SPI1 protein was detected in Norway spruce seedlings and found to accumulate in roots during development. Notably, the putative plant defensin SPI1 lined the wall of cortical root cells, and in roots invaded by P. dimorphum the SPI1 protein was found associated with the invading hyphae. This supports the hypothesis that SPI1 has a role in the defense against pathogenic oomycetes and fungi. The possible protective role of prior colonization by the ectomycorrhizal fungus on later challenge with the pathogen C. polonica, previously known to be vectored to the tree stem by bark beetles, was also examined. Surprisingly, C. polonica was able to invade also roots of both mycorrhizal and non-mycorrhizal seedlings. Not only induced or enhanced plant responses were observed, but also reduced levels of defense-related proteins were observed in the infected roots at the later stages of infection. Decreased levels of SPI1was detected within 96 hours after infection in response to the pathogens tested. Reduced levels of the corresponding transcript was also detected indicating a suppression of host responses by the pathogens. Increased proteolytic activity was detected in infected roots, and from the pathogens. Proteolytic degradation of host proteins by fungal secreted proteases may reduce the levels of potentially antimicrobial proteins enabling the pathogens to effectively invade the roots. Reduced levels of the SPI1 in roots, was found also in response to the ectomycorrhizal fungus L. bicolor. Reduced levels of the peroxidase isozymes at the later stages of the infections, was also observed. Thus, suppressor(s) may be produced by both the pathogens and by the ectomycorrhizal fungus during infection, reducing the host responses and contributing to successful colonization of the roots.
Authors
Tor J. JohansenAbstract
No abstract has been registered
Authors
J. Peter HallAbstract
No abstract has been registered
Authors
A.S. IsaevAbstract
No abstract has been registered
Authors
Anthony A. Hopkin J. Peter HallAbstract
No abstract has been registered
Authors
Maury E. Bredahl Nils Kristian Nersten Sjur Spildo PrestegardAbstract
No abstract has been registered
Abstract
The objective structure of parameters of soil acidity and cation exchange properties of podzols affected by the emission of the Pechenganikel factory (the Kola Peninsula) is revealed. The multiparametric analysis of soil properties and the traditional correlation analysis complement one another. They point to the complex character of interrelations between soil properties in conditions of progressing human-induced acisification.
Authors
A. Kinnunen P. PulkkinenAbstract
No abstract has been registered