Publikasjoner
NIBIOs ansatte publiserer flere hundre vitenskapelige artikler og forskningsrapporter hvert år. Her finner du referanser og lenker til publikasjoner og andre forsknings- og formidlingsaktiviteter. Samlingen oppdateres løpende med både nytt og historisk materiale. For mer informasjon om NIBIOs publikasjoner, besøk NIBIOs bibliotek.
2010
Forfattere
Igor A. Yakovlev Carl Gunnar Fossdal Øystein JohnsenSammendrag
Norway spruce (Picea abies (L.) H. Karst.) displays a temperature-dependent epigenetic memory from the time of embryo development, which thereafter influences the timing of bud phenology. As a first step toward unravelling the molecular mechanism behind an epigenetic memory, transcriptional analysis was performed on seedlings from seeds of six full-sib families produced under cold (CE) and warm (WE) embryogenesis temperature regimes. We prepared two suppressive subtracted cDNA libraries, representing genes predominantly expressed after bud set induction in plants from seeds obtained after CE and WE embryogenesis. Sequencing and annotation revealed considerable differences in the transcriptome of WE and CE seedlings. We studied the expression patterns of 32 selected candidate genes using qRT-PCR. Five genes, two transposon-related genes and three with no matching sequence in databases showed differential expression in progeny from CE and WE correlated with family differences. Another step was to study microRNAs (miRNAs), which are endogenous small RNAs exerting epigenetic gene regulatory effects. We tested for their presence and differential expression. We then prepared concatemerized small RNA libraries from seedlings of two fullsib families, originated from seeds developed in a cold or a warm environment. One family showed distinct epigenetic effects whilst the other did not. Sequencing identified 24 novel and 4 conserved miRNAs. Further search and screening of the conserved miRNAs confirmed the presence of 17 additional miRNAs. Most of the miRNAs were targeted to unknown genes. The expression of seven conserved and nine novel miRNAs showed significant differences in transcript levels in the full-sib family showing distinct epigenetic difference in bud set, but not in the non-responding full-sib family. The differential expression of specific miRNAs indicates their putative participation in epigenetic regulation. Putative miRNA targets were studied. These findings may contribute to our understanding of the epigenetic mechanisms underlying adaptive changes acquired during embryogenesis in Norway spruce.
Forfattere
Nadeem Yaqoob Jan Karlsson Benedicte Riber Albrectsen Halvor Solheim Carl Gunnar FossdalSammendrag
Plants are exposed to a variety of pathogens in their natural habitats. To understand the key processes of defense responses in aspen (Populus tremulae) at the transcript level two clones C72 and C23 with differential level of resistance from the SwAsp collection were inoculated with a foliar rust (Melampsora magnusiana Wagnar). Leaf samples were collected from adjacent areas of the inoculation site to examine the long distance (systemic) defense responses at day1, day3 and day14 post treatments. We performed microarray experiments on the biothrophic interaction, on comparison with the healthy controls we found that the two clones respond in a widely different fashion to the rust. Clone C23 showed almost no response to biotroph after 24 hours while clone 72 gave a clear defense response to the pathogen. Quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR) showed a significant differential expression patterns in susceptible and resistant colnes. Chitinase, cinnamic acid reductase and the iaa genes showed signification up-regulation in resistant clone. The level of expression was 5.9 delta threshold cycles in chitinase gene at day14. Data analysis from extracted total phenolics and condensed tannins verify the results of cDNA arrays and qRT-PCR.
Sammendrag
Today the spruce bark beetle Ips typographus is always univoltine in Northern Europe including Norway and completes development from egg to adult between May and August. Further south in Europe, development is bivoltine with the completion of two generations in most years. A temperature-driven developmental model suggests that by 2070-2100 the voltinism of I. typographus will change dramatically in Norway. If summers become only 2.5°C warmer than today bivoltinism can be expected every single year in the major spruce growing areas in S-Norway. This is likely to have dramatic effects on forestry since two generations per year will give two, instead of one, attack periods each summer. In addition to increasing the number of attacked trees the effect of the attacks may also be more severe, as Norway spruce is more susceptible to beetle attacks later in the summer. However, climate change will probably also change the phenology of Norway spruce and thus its susceptibility to attack by I. typographus and its phytopathogenic fungal associates. We are currently modelling how tree resistance varies with temperature and tree phenology in order to provide more well-founded advice to forest managers on the interaction between bark beetles and tree in a future climate.
Forfattere
Paal KrokeneSammendrag
The interaction between conifers, ophiostomatoid fungi and bark beetles is a key factor in conifer ecosystems worldwide, since combined beetle-fungus attacks may cause massive tree mortality, huge economical losses and landscape-level ecological changes. For more than a century researchers have been arguing about who is responsible for tree mortality in bark beetle attacked trees - the beetles themselves or their associated fungi. As in many such polarized debates the best answer probably lies somewhere in between the extremes. The beetles are obviously central in tree killing, as they are actively selecting suitable host trees, short-circuiting tree defenses by boring straight into the relatively defenseless cambial area, and causing mechanical damage to the phloem. However, ophiostomatoid fungi are equally obvious contributors to tree death since nearly all tree-killing bark beetles are associated with such fungi, these fungi are able to colonize and kill healthy phloem and sapwood far beyond the beetle tunnels, and many fungi can kill healthy trees in experimental mass-inoculations. Thus, the trees are facing a beetle-fungus complex that probably acts synergistically to overwhelm tree defenses. The beetles’ mass-attack strategy is central to the success of the beetle-fungus complex, since multiple attacks deplete tree defenses and speed up tree-killing.
Forfattere
Knut Magnar Sandland Peder GjerdrumSammendrag
The objective of the research work has been to investigate whether the quality of dried and planed sawn timber can be improved by sorting logs and planks before the drying process. The research material was selected by randomly choosing 30 butt logs and 30 middle logs in a given diameter class at a sawmill. The logs were sawn in a 4 x log pattern, and one inner plank (near pith) and one outer plank (near bark) were chosen from each log. Various properties were measured on the logs and on the sawn timber before and after drying. The material was then planed, and the quality of the panel boards was registered. Based on the results, different models for sorting the timber before drying to optimise the drying process are proposed. One of them is to separate outer and inner planks. An evident improvement is then expected, both due to possibilities for adjusting the drying process to the moisture content before and after drying, and the possibilities for optimising the drying process in accordance with the requirements of the various wood products. In addition to a separation of inner and outer planks, it is also of interest to separate planks from different types of logs (e.g. butt logs and middle logs) to be able to further optimise the drying process according to the wood properties. The project results also show that the best wood quality for production of panel boards is found in the inner planks from middle logs, mainly due to the knot pattern in the stems.
Forfattere
Lone Ross GobakkenSammendrag
An evident change in climate the last decades has been recorded, and combined effects of increased CO2, elevated temperature and altered precipitation regimes have been observed to represent a change to the fundamental drivers within ecosystems. Growth of moulds, both in nature and on man-made constructions and objects, will most likely increase due to changes in the climate. The survival, the reproduction, the dispersal and the geographic distribution of moulds are decided by both direct and indirect effects of climate change. Not only the moulds, but also their hosts and substrates, possible competitors and enemies will be affected by climate change. It is essential to understand the interactions between the members in these ecosystems to be able to control and predict future development of moulds. The effect of introducing new building directives, environmental friendly materials and products which are meant to oblige the demand for more climate friendly buildings and houses, is an aspect that may generate unexpected and unintended mould growth on man-made constructions and objects. Future research should focus on the interaction between the moulds, the hosts, the substrates and the climatic factors, and what implications future changes in building directives and housing policy will have on mould growth.
Sammendrag
Understanding the feedback between terrestrial biosphere processes and meteorological drivers is crucial to ecosystem research as well as management. For example, remote sensing of the activity of vegetation in relation to environmental conditions provides an invaluable basis for investigating the spatiotemporal dynamics and patterns of variability. We investigate the Fraction of Absorbed Photosynthetically Active Radiation (fAPAR) using SeaWiFS satellite observations from 1998 to 2005 and ancillary meteorological variables from the CRU-PIK dataset. To what extent do precipitation and temperature dominate the terrestrial photosynthetic activity on monthly to interannual time scales? A spectral decomposition using Singular System Analysis leads to a global ‘classification’ of the terrestrial biosphere according to prevalent time-scale dependent dynamics of fAPAR and its relation to the meteorology. A complexity analysis and a combined subsignal extraction and dimensionality reduction reveals a series of dominant geographical gradients, separately for different time scales. Here, we differentiate between three time scales: on short time scales (compared to the annual cycle), variations in fAPAR coincide with corresponding precipitation dynamics. At the annual scale, which explains around 50% of the fAPAR variability as a global average, patterns largely resemble the biomes of the world as mapped by biogeographic methods.At longer time scales, spatially coherent patterns emerge which are induced by precipitation and temperature fluctuations combined. However, we can also identify regions where the variability of fAPAR on specific time scales cannot be traced back to climate and is apparently shaped by other geoecological or anthropogenic drivers. http://uregina.ca/prairies/assets/Prairie_Summit_Final_Program.pdf
Forfattere
Igor A. Yakovlev Carl Gunnar Fossdal Øystein JohnsenSammendrag
The temperature level experienced during zygotic embryogenesis in the conifer Norway spruce effects an epigenetic memory and vital phenological traits in the progeny (Kvaalen & Johnsen, 2008). MicroRNAs (miRNAs) are endogenous small RNAs having large-scale regulatory effects on plant development and could participate in epigenetic regulation of expression in plants. To unravel the possible molecular mechanisms behind this epigenetic phenomenon we prepared two concatemerized small RNA libraries representing smallRNAs expressed in plants from seeds obtained after embryogenesis in cold environment and in a warm environment and made a search of conserved miRNAs found in other plant species. Partial sequencing of the libraries allowed identifying of 199 different small RNAs, with predominant length of 21-nt. Among them were 24 novel candidate miRNAs and 4 conserved. Screening of conserved miRNAs allowed confirming additional 17 miRNAs belonged to 11 miRNA families. Most of the miRNA obtained were related to unknown and “no-hit” genes. The expression of 8 conserved miRNAs (pab-miR156c, 159a, 396a,b, 535, 947, 951 and 858) and 9 predicted miRNAs (miR080, 100, 105, 119, 122, 132, 144a,b and 157) showed significant differences in transcript levels between epigenetically distinct plants. Additionally we confirmed that four selected genes PaLPT4, PaGaMYB, PaMYB10 and PaSPB13 regulated by miRNAs pab-miR100, 858, 159a and 156c, may also be involved in epigenetic memory regulation. Our results suggest that Norway spruce miRNAs are composed of a set of conserved miRNAs and a large proportion of novel non-conserved miRNAs with relatively low expression levels. These findings imply that both kinds of miRNAs might be involved or at least affected by the molecular mechanisms underlying the temperature sensitive epigenetic memory in Norway spruce.
Sammendrag
In European forests, standing stocks are currently higher than ever during the last decades, in part due to reduced logging or the abandonment of agricultural land. However, data from intensive monitoring plots reveal an increased growth even without direct human intervention.We used a set of 363 plots from 16 European countries to investigate the influence of environmental factors on forest growth: nitrogen, sulphur and acid deposition, temperature, precipitation and drought, for Norway spruce, Scots pine, common beech and European as well as sessile oak.We used existing information on site productivity, stand age and stand density to estimate expected growth. Relative tree growth, i.e., the ratio between actual growth within a five-year period and expected growth, was then related to environmental factors in a stepwise multiple regression.The results consistently indicate a fertilizing effect from nitrogen deposition, with roughly one percent increase in site productivity per kg of nitrogen deposition per ha and year, or 20 kg C fixation per kg N deposition. This was most pronounced for plots having soil C/N ratios above 25. We also found a positive albeit less clear relationship between relative growth and summer temperatures.From the study, we cannot conclude on any detrimental effects on growth from sulphur and acid deposition or from drought periods. A very recent study from the U.S., comprising 4800 plots and 24 tree species, confirms our results. However, we also show that the magnitude of N deposition effects on global forest C balance is currently a highly controversial matter, and comment on this debate. http://www.cef-cfr.ca/uploads/Colloque/Programme10_5.pdf
Forfattere
Igor A. Yakovlev Ari M. Hietala Pierre-Emmanuel Courty Francis Martin Jan Stenlid Halvor Solheim Carl Gunnar FossdalSammendrag
The genome H. annosum s.l. was sequenced by JGI to a 8.23X coverage and assembled into 39 scaffolds with a total size of 33.7 Mb covering more than 98% of the whole genome. Based of genome sequence we annotated a number of genes for fungal enzymes that are believed to participate in lignin degradation, including: laccases (Lcc18 genes), manganese peroxidases (MnP8 genes) and hydrogen peroxide forming enzymes such as glyoxal oxidases (GLOX5 genes), quinone oxidoreductases (QOR17 genes) and aryl alcohol oxidases (AAO16 genes), which is in concordance with these gene family sizes observed in other sequenced white-rot fungi. We studied the genomic organisation and phylogeny of these genes as well as their expression using NimbleGen arrays and qRT-PCR. Transcript profiling using whole-genome oligo arrays and qRT-PCR revealed that some transcripts were very abundant in lignin-rich media (Lcc5 15, MnP2, GLOX4, QOR2 10, AAO9), in cellulose-rich media (lcc2, 7 16, MnP3 4, GLOX3, QOR4 6, AAO2, 7 10), in wood (Lcc3, MnP4, QOR2, GLOX1, AAO10) or in the free-living mycelium grown liquid culture (Lcc1, 3, 10 13), suggesting specific functions of these genes, which need to be studied further.