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.
2012
Authors
Carl Gunnar Fossdal Nadeem Yaqoob Paal Krokene Harald Kvaalen Halvor Solheim Igor A. YakovlevAbstract
Background: NB-LRR resistance proteins are involved in recognizing pathogens and other exogenous stressors in plants. Resistance proteins are the first step in induced defence responses and a better understanding of their regulation is important to understand the mechanisms of plant defence. Much of the post-transcriptional regulation in plants is controlled by microRNAs (miRNA). We examined the expression of five Norway spruce miRNA that may regulate NB-LRR related transcripts in secondary phloem (bark) of resistant Norway spruce after wounding and inoculation with the necrotrophic blue stain fungus Ceratocystis polonica. Results: The plants of this clone recovered from both the pathogen inoculations and wounding alone. We found local and systemic induction of the resistance marker genes PaChi4, PaPAL and PaPX3 indicative of an effective induced host defence response. There were minor local and systemic changes in the expression of five miRNAs and 21 NB-LRRs between healthy and treated plants. Only five putative NB-LRRs (PaLRR1, PaLRR3, PaLRR14, PaLRR15 and PaLRR16) showed significant increases greater than two-fold as a local response to C. polonica. Of all NB-LRRs only PaLRR3, the most highly differentially regulated NB-LRR, showed a significant increase also due to wounding. The five miRNAs showed indications of an initial local and systemic down-regulation at day 1, followed by a later increase up to and beyond the constitutive levels at day 6. However, the initial down-regulation was significant only for miR3693 and miR3705. Conclusions: Overall, local and systemic expression changes were evident only for the established resistance marker genes and PaLRR3. The minor expression changes observed both for the followed miRNAs and their predicted NB-LRR targets suggest that the expression of most NB-LRR genes are maintained close to their constitutive levels in stressed and healthy Norway spruce plants.
Authors
Karen Refsgaard Ingrid GuldvikAbstract
No abstract has been registered
Authors
Sheng-Hong Li Nina Elisabeth Nagy Almuth Hammerbacher Paal Krokene Xue-Mei Niu Jonathan Gershenzon Bernd SchneiderAbstract
Norway spruce (Picea abies) bark contains specialized phloem parenchyma cells that swell and change their contents upon attack by the bark beetle Ips typographus and its microbial associate, the blue stain fungus Ceratocystis polonica. These cells exhibit bright autofluorescence after treatment with standard aldehyde fixatives, and so have been postulated to contain phenolic compounds. Laser microdissection of spruce bark sections combined with cryogenic NMR spectroscopy demonstrated significantly higher concentrations of the stilbene glucoside astringin in phloem parenchyma cells than in adjacent sieve cells. After infection by C. polonica, the flavonoid (+)-catechin also appeared in phloem parenchyma cells and there was a decrease in astringin content compared to cells from uninfected trees. Analysis of whole-bark extracts confirmed the results obtained from the cell extracts and revealed a significant increase in dimeric stilbene glucosides, both astringin and isorhapontin derivatives (piceasides A to H), in fungus-infected versus uninfected bark that might explain the reduction in stilbene monomers. Phloem parenchyma cells thus appear to be a principal site of phenolic accumulation in spruce bark.
Authors
Lone Ross Gobakken Mats WestinAbstract
Environmentally sound wooden facades with long service lives and acceptable appearance are desired. Several types of modified wood are used in building applications to fulfil those requirements, but there is a potential for using more modified wood material. In facades modified wood are often used without any surface treatment or coating, but some sort of coating are desired and requested in a segment of the potential marked. Finding suitable coating systems for modified wood can be a challenge, and the objective of this study was to evaluate the long time performance of modified wood substrates in combinations with different coating systems after 8 years of outdoors exposure. Furthermore, evaluations at 4 and 8 years were compared to study the quantitative mould growth in a very late stage of the test period to capture any deviant behaviour from the traditional growth curve. Three coating systems were applied on furfurylated Scots pine, acetylated Scots pine, thermally modified Scots pine, oil/thermally modified Scots pine, thermally modified Norway spruce, and three reference wood substrates, and exposed outdoors for 8 years to evaluate their ability to resist surface moulds and blue stain fungi, cracking and flaking. The test was carried out according to EN 927-3. After 8 years mould growth, cracking and flaking mainly varied with type of coating where the tendency was that a waterborne system had the lowest rating for both mould growth, cracking and flaking. Oil/thermally modified treated pine had the lowest mould rating of the modified substrates. Acetylated pine had a decrease in mould rating from year 4 to year 8 when coated with the best coating system and a very small increase when coated with the second best system. Acetylated pine tended to have less flaking than the other modified substrates. Furthermore, acetylated pine, thermally modified pine and thermally modified spruce tended to have the least cracking of the modified wood substrates.
Authors
Christer MagnussonAbstract
No abstract has been registered
Authors
Christer MagnussonAbstract
No abstract has been registered
Authors
Even Riiser Ingrid Holtsmark Hege Særvold Steen S. Swaminathan Navin Khanna Ralph Bock Jihong Liu ClarkeAbstract
No abstract has been registered
Authors
Even Riiser Ingrid Holtsmark Hege Særvold Steen S. Swaminathan Navin Khanna Ralph Bock Jihong Liu ClarkeAbstract
The global spread of dengue fever threatens a large percentage of the world’s population. The disease causes great human suffering, a high mortality from dengue haemorrhagic fever and its complications, and major costs. There is currently no vaccine to prevent dengue virus infection. Our project aims to express a tetravalent vaccine candidate in tobacco chloroplasts, a cost effective system, and hence to contribute to innovation and bio-economy as a long term goal.
Abstract
Fire is the most important ecological factor governing boreal forest stand dynamics. In low- to moderate-severity fires, the post-fire growth of the surviving trees varies according to fire frequency, intensity and site factors. Little is known about the growth responses of Scots pine (Pinus sylvestris L.) following fires in boreal forests. We quantified changes in tree growth in the years following 61 historical forest fires (between 1210 and 1866) in tree-ring series collected from fire-scarred Scots pine trees, snags and stumps in Trillemarka nature reserve in south-central Norway. Basal area increment 10 years pre-, 5 years post-, and 11-20 years post-fire were calculated for 439 fire scars in 225 wood samples. We found a slight temporary growth reduction 5 years post-fire followed by a marked growth increase 11-20 years post-fire. Beyond 20 years post-fire, the long-term tree growth declined steadily up to approximately 120 years. Our results indicate that recurring fires maintained high tree growth in remnant Scots pines, most probably due to a reduction in tree density and thus decreased competition.
Authors
Ghislain Tchoromi Tepa-Yotto Trond Hofsvang Ignace Godonou May SæthreAbstract
The solitary parasitic wasp Lysiphlebus testaceipes, is a species native to North America. The species has a broad aphid host range and has been accidentally spread or introduced as a biocontrol agent to many regions of the world. In Benin, L. testaceipes is a newly found species, and it is the dominating primary parasitoid of aphids on vegetables.