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.
2021
Authors
Kirill Ovchinnikov Christian Kranjec Amar A. Telke Morten Kjos Tage Thorstensen Dzung B. DiepAbstract
No abstract has been registered
Authors
Klaus. R Westphal Simone Bachleitner Manja M. Severinsen Mathias L. Brundtø Frederik T. Hansen Trine Sørensen Rasmus D. Wollenberg Erik Lysøe Lena Studt Jens L. Sørensen Teis E. Sondergaard Reinhard WimmerAbstract
The plant pathogenic fungus Fusarium graminearum is known to produce a wide array of secondary metabolites during plant infection. This includes several nonribosomal peptides. Recently, the fusaoctaxin (NRPS5/9) and gramilin (NRPS8) gene clusters were shown to be induced by host interactions. To widen our understanding of this important pathogen, we investigated the involvement of the NRPS4 gene cluster during infection and oxidative and osmotic stress. Overexpression of NRPS4 led to the discovery of a new cyclic hexapeptide, fusahexin (1), with the amino acid sequence cyclo-(d-Ala-l-Leu-d-allo-Thr-l-Pro-d-Leu-l-Leu). The structural analyses revealed an unusual ether bond between a proline Cδ to Cβ of the preceding threonine resulting in an oxazine ring system. The comparative genomic analyses showed that the small gene cluster only encodes an ABC transporter in addition to the five-module nonribosomal peptide synthetase (NRPS). Based on the structure of fusahexin and the domain architecture of NRPS4, we propose a biosynthetic model in which the terminal module is used to incorporate two leucine units. So far, iterative use of NRPS modules has primarily been described for siderophore synthetases, which makes NRPS4 a rare example of a fungal nonsiderophore NRPS with distinct iterative module usage.
Authors
Paal Krokene Bjørn Arild Hatteland Christer Magnusson Daniel Flø Iben Margrete Thomsen Johan A. Stenberg May Bente Brurberg Per Hans Micael Wendell Mogens Nicolaisen Simeon Rossmann Venche Talgø Beatrix Alsanius Sandra A.I. Wright Trond RafossAbstract
No abstract has been registered
Authors
Daniel Powell Ewald Groβe-Wilde Paal Krokene Amit Roy Amrita Chakraborty Christer Löfstedt Heiko Vogel Martin N. Andersson Fredrik SchlyterAbstract
Conifer-feeding bark beetles are important herbivores and decomposers in forest ecosystems. These species complete their life cycle in nutritionally poor substrates and some can kill enormous numbers of trees during population outbreaks. The Eurasian spruce bark beetle (Ips typographus) can destroy >100 million m3 of spruce in a single year. We report a 236.8 Mb I. typographus genome assembly using PacBio long-read sequencing. The final phased assembly has a contig N50 of 6.65 Mb in 272 contigs and is predicted to contain 23,923 protein-coding genes. We reveal expanded gene families associated with plant cell wall degradation, including pectinases, aspartyl proteases, and glycosyl hydrolases. This genome sequence from the genus Ips provides timely resources to address questions about the evolutionary biology of the true weevils (Curculionidae), one of the most species-rich animal families. In forests of today, increasingly stressed by global warming, this draft genome may assist in developing pest control strategies to mitigate outbreaks.
Authors
Tomáš Hlásny Louis König Paal Krokene Marcus Lindner Claire Montagné-Huck Jörg Müller Hua Qin Kenneth F. Raffa Mart-Jan Schelhaas Miroslav Svoboda Heli Viiri Rupert SeidlAbstract
Purpose of Review Outbreaks of tree-killing bark beetles have reached unprecedented levels in conifer forests in the northern hemisphere and are expected to further intensify due to climate change. In parts of Europe, bark beetle outbreaks and efforts to manage them have even triggered social unrests and political instability. These events have increasingly challenged traditional responses to outbreaks, and highlight the need for a more comprehensive management framework. Recent Findings Several synthesis papers on different aspects of bark beetle ecology and management exist. However, our understanding of outbreak drivers and impacts, principles of ecosystem management, governance, and the role of climate change in the dynamics of ecological and social systems has rapidly advanced in recent years. These advances are suggesting a reconsideration of previous management strategies. Summary We synthesize the state of knowledge on drivers and impacts of bark beetle outbreaks in Europe and propose a comprehensive context-dependent framework for their management. We illustrate our ideas for two contrasting societal objectives that represent the end-members of a continuum of forest management goals: wood and biomass production and the conservation of biodiversity and natural processes. For production forests, we propose a management approach addressing economic, social, ecological, infrastructural, and legislative aspects of bark beetle disturbances. In conservation forests, where non-intervention is the default option, we elaborate under which circumstances an active intervention is necessary, and whether such an intervention is in conflict with the objective to conserve biodiversity. Our approach revises the current management response to bark beetles in Europe and promotes an interdisciplinary social-ecological approach to dealing with disturbances.
Authors
Paal KrokeneAbstract
No abstract has been registered
Abstract
The spruce bark beetle Ips typographus is the most damaging pest in European spruce forests and has caused great ecological and economic disturbances in recent years. Although native to Eurasia, I. typographus has been intercepted more than 200 times in North America and could establish there as an exotic pest if it can find suitable host trees. Using in vitro bioassays, we compared the preference of I. typographus for its coevolved historical host Norway spruce (Picea abies) and two non-coevolved (naïve) North American hosts: black spruce (Picea mariana) and white spruce (Picea glauca). Additionally, we tested how I. typographus responded to its own fungal associates (conspecific fungi) and to fungi vectored by the North American spruce beetle Dendroctonus rufipennis (allospecific fungi). All tested fungi were grown on both historical and naïve host bark media. In a four-choice Petri dish bioassay, I. typographus readily tunneled into bark medium from each of the three spruce species and showed no preference for the historical host over the naïve hosts. Additionally, the beetles showed a clear preference for bark media colonized by fungi and made longer tunnels in fungus-colonized media compared to fungus-free media. The preference for fungus-colonized media did not depend on whether the medium was colonized by conspecific or allospecific fungi. Furthermore, olfactometer bioassays demonstrated that beetles were strongly attracted toward volatiles emitted by both con- and allospecific fungi. Collectively, these results suggest that I. typographus could thrive in evolutionary naïve spruce hosts if it becomes established in North America. Also, I. typographus could probably form and maintain new associations with local allospecific fungi that might increase beetle fitness in naïve host trees.
Lecture – Natural disturbance factors affecting forests and possible mitigation actions
Paal Krokene
Authors
Paal KrokeneAbstract
No abstract has been registered
Abstract
In 2018, up to 4 million m3 Norway spruce was killed by the spruce bark beetle Ips typographus in Sweden. The event was unique for Sweden, in terms of both affected volume and the fact that it was triggered by severe drought stress, not by ample availability of relatively defenseless storm-felled trees. The outbreak continued in 2019 and 2020, each year with twice as many trees killed as in 2018. The aim of this study was to quantify seasonal variation and potential lag-effects in tree defense capacity the year after a severe drought stress. Inoculation with a bark beetle-associated bluestain fungus, repeated four times with one-month-intervals between May and August 2019, were carried out at three field sites with spruce provenances of Swedish and East European origin representing early and late bud burst, respectively. All sites had experienced moderate to severe drought stress in 2018, and site-specific defense capacity correlated positively with the cumulative precipitation two months before inoculation. Sites with two-month precipitation levels <100 mm had larger necrotic lesions in the phloem following inoculation, an indication of lower tree defense capacity. Lesion size did not differ between provenances, and all trees were able to confine fungal infection successfully. There were some seasonal differences in necrotic lesion size, with the sites Skärsnäs and Norberg having significantly larger lesions in June than in May, and site Lugnet having large lesions also in May. Lesions were generally smaller in July and August than in June. The cross-sectional area and number of traumatic resin ducts was measured in sapwood samples from one site, Lugnet, to quantify an additional aspect of tree defenses. The area of resin ducts produced in May and June were larger than that in July and August. This is in line with a positive correlation between lesion area and resin duct area, indicating that a stronger fungal infection following inoculation in spring triggered a stronger induced defense response. The East European provenances had more resin ducts than Swedish provenances, but the area of resin ducts did not differ significantly between provenances.
Authors
Paal KrokeneAbstract
No abstract has been registered