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
Tore SkrøppaAbstract
Forests and wooded land cover 39 % of the land area of Norway and productive forest amounts to 8.3 million hectares. Two conifer species, Picea abies and Pinus sylvestris, dominate the forest area; they cover 71 % of the forest area and 84 % of total volume. The annual harvest is at present less than 50 % of the annual increment. Forestry and the wood industry have great financial importance in Norway, and timber and wood products have a gross value of 5 % of the total gross domestic product. Forestry is characterized by small-scale properties which to a large extent are privately owned. The main objective of the forest policy is to promote sustainable forest management with a view to promote active, local and economic development, and to secure biological diversity, considerations for the landscape, outdoor recreation and the cultural values associated with the forest. Forest management plans are important instruments to obtain these goals. Three targeted programmes have high priority in the present forest policy: forests and climate, increased use of wood and bioenergy. Active use of the forest genetic resources may contribute to the success of these programmes. Species composition and distribution of forest trees in Norway is largely determined by the following factors: the invasion of tree species after the Ice Age, subsequent climatic changes and human activities ....
Authors
Tore SkrøppaAbstract
No abstract has been registered
Authors
Laura Parducci Tina Jørgensen Mari Mette Tollefsrud Ellen Elverland Torbjørn Alm Sonia L. Fontana Keith D. Bennett James Haile Irina Matetovici Yoshihisa Suyama Mary E. Edwards Kenneth Andersen Morten Rasmussen Sanne Boessenkool Eric Coissac Christian Brochmann Pierre Taberlet Michael Houmark-Nielsen Nicolaj K. Larsen Ludovic Orlando M. Thomas P. Gilbert Kurt H. Kjær Inger Greve Alsos Eske WillerslevAbstract
No abstract has been registered
Authors
Laura Parducci Mary E. Edwards Keith D. Bennett Torbjørn Alm Ellen Elverland Mari Mette Tollefsrud Tina Jørgensen Michael Houmark-Nielsen Nicolaj Krog Larsen Kurt H. Kjær Sonia L. Fontana Inger Greve Alsos Eske WillerslevAbstract
Birks et al. question our proposition that trees survived the Last Glacial Maximum (LGM) in Northern Scandinavia. We dispute their interpretation of our modern genetic data but agree that more work is required. Our field and laboratory procedures were robust; contamination is an unlikely explanation of our results. Their description of Endletvatn as ice-covered and inundated during the LGM is inconsistent with recent geological literature.
Authors
Igor A. Yakovlev Carl Gunnar Fossdal Tore Skrøppa Jorunn Elisabeth Olsen Anne Hopen Jahren Øystein JohnsenAbstract
Conifers are evolutionarily more ancient than their angiosperm counterparts, and thus some adaptive mechanisms and features influenced by epigenetic mechanisms appear more highly displayed in these woody gymnosperms. Conifers such as Norway spruce have very long generation times and long life spans, as well as large genome sizes. This seemingly excessive amount of genomic DNA without apparent duplications could be a rich source of sites for epigenetic regulation and modifications. In Norway spruce, an important adaptive mechanism has been identified, called epigenetic memory. This affects the growth cycle of these trees living in environments with mild summers and cold winters, allowing them to adapt rapidly to new and/or changing environments. The temperature during post-meiotic megagametogenesis and seed maturation epigenetically shifts the growth cycle programme of the embryos. This results in significant and long-lasting phenotypic change in the progeny, such as advance or delay of vital phenological processes of high adaptive value, like bud break and bud set. This phenomenon is not only of important evolutionary significance but has clear practical implications for forest seed production and conservation of forest genetic resources. The underlying molecular mechanism that causes the ‘memory’ in long-lived woody species is currently under investigation. Here we summarize the information related to epigenetic memory regulation in gymnosperms, with special emphasis on conifers. The molecular mechanism behind this is still unknown but transcriptional changes are clearly involved. Epigenetic regulation may be realized through several mechanisms, including DNA methylation, histone modification, chromatin remodelling, small non-coding RNAs and transposable element regulation, of which non-coding RNAs might be one of the most important determinants.
Authors
Igor A. Yakovlev YeonKyeong Lee Bjørn Rotter Tore Skrøppa Øystein Johnsen Jorunn Elisabeth Olsen Carl Gunnar FossdalAbstract
Epigenetic memory marks establishment in Norway spruce occur exclusively during embryogenesis in response to environmental impact, and the epitype is fixated by the time the embryo is fully developed without a change in the DNA sequence. We started large scale studies aimed on identifying and characterizing of genes and regulatory elements involved in the initiation, maintenance, and heritability of epigenetic memory using candidate genes and next generation sequencing approaches. Molecular mechanisms of formation of epigenetic memory were studied on the same full-sibs family zygotic embryo in vitro cultures developed in cold (18°C) and warm (30°C) environmental conditions from proliferation till mature embryo stages. Initially we had found large set (64) of Arabidopsis epigenetic regulator gene homologs in spruce. In general, known epigenetic related genes are very well represented among spruce ESTs. Analysis of the transcription patterns of these genes using RT-PCR in epigenetically different embryogenic samples reveal specific transcription patterns on different stages of embryogenic development dependent on epitype. We are expecting to determine certain stages during embryogenesis when epigenetic memory marks are forming. At the same time, nearly no differences in transcription levels of studied genes had been found in seedlings (4 month old), originated from full-sib families clearly differed in epigenetic response. Using MACE (massive cDNA 3-end sequencing) deep mRNA sequencing on the Illumina GSII platform, we analyzed P. abies transcriptomes by comparison warm and cold originated “embryonic epitypes” developed in cold and warm environmental conditions. Significant differences in transcriptomes between epitypes revealed by high-throughput sequencing will be discussed.
Abstract
Ceratocystis polonica and Heterobasidion parviporum are important fungal pathogens in Norway spruce (Picea abies). Tree susceptibility to these pathogens with respect to phenology was studied using artificial fungal inoculations at six stages of bud development, and assessed by measuring phloem necroses in the stems of 2- and 8-year-old trees. Tree capacity for resistance was assessed by measuring phloem nonstructural carbohydrates at each stage. Phloem necroses were significantly larger in trees with fungal versus control inoculations and increased significantly over time. Changes in nonstructural carbohydrates occurred in the trees; a significant decline in starch and a slight but significant increase in total sugars occurred over time. These results suggest that susceptibility to fungal pathogens and carbohydrate levels in the stems of the trees were related to fine-scale changes in bud development. A trade-off may occur between allocation of starch (the major fraction of the stem carbohydrate pool) to bud development/shoot growth versus defence of the stem. Previous tests of plant defence hypotheses have focused on herbivory on plants growing under different environmental conditions, but the role of phenology and the effect of pathogens are also important to consider in understanding plant resource allocation patterns.
2011
Authors
Ishita Ahuja Birgit Hafeld Borgen Magnor Kåre Hansen Bjørn Ivar Honne Caroline Müller Jens Rohloff John Trevor Rossiter Atle M. BonesAbstract
No abstract has been registered
Authors
Aparna Tiwari Adam Vivian-Smith Roeland E. Voorrips Myckel E.J. Habets Lin B. Xue Remko Offringa Ep HeuvelinkAbstract
Background Parthenocarpy is a desirable trait in Capsicum annuum production because it improves fruit quality and results in a more regular fruit set. Previously, we identified several C. annuum genotypes that already show a certain level of parthenocarpy, and the seedless fruits obtained from these genotypes often contain carpel-like structures. In the Arabidopsis bel1 mutant ovule integuments are transformed into carpels, and we therefore carefully studied ovule development in C. annuum and correlated aberrant ovule development and carpelloid transformation with parthenocarpic fruit set. Results We identified several additional C. annuum genotypes with a certain level of parthenocarpy, and confirmed a positive correlation between parthenocarpic potential and the development of carpelloid structures. Investigations into the source of these carpel-like structures showed that while the majority of the ovules in C. annuum gynoecia are unitegmic and anatropous, several abnormal ovules were observed, abundant at the top and base of the placenta, with altered integument growth. Abnormal ovule primordia arose from the placenta and most likely transformed into carpelloid structures in analogy to the Arabidopsis bel1 mutant. When pollination was present fruit weight was positively correlated with seed number, but in the absence of seeds, fruit weight proportionally increased with the carpelloid mass and number. Capsicum genotypes with high parthenocarpic potential always showed stronger carpelloid development. The parthenocarpic potential appeared to be controlled by a single recessive gene, but no variation in coding sequence was observed in a candidate gene CaARF8. Conclusions Our results suggest that in the absence of fertilization most C. annuum genotypes, have parthenocarpic potential and carpelloid growth, which can substitute developing seeds in promoting fruit development.
Abstract
No abstract has been registered