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- Arnerup Christiansson, Jenny
(author)
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Induced defence responses in Picea abies triggered by Heterobasidion annosum s.l
- 2011
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Doctoral thesis (other academic/artistic)abstract
- Norway spruce [Picea abies (L.)Karst.] is a key tree species for forest industry in Europe and stem and butt rot caused by Heterobasidion parviporum (Fr.) Niemelä & Korhonen is one of its major disease problems. The commercial gain using improved plant material could be even greater if resistance traits were included in the breeding program. The aim of this study was to increase the knowledge of the induced defences in response to H. annosum s.l. in Norway spruce bark. In this thesis it has been concluded that there is a significant variation between genotypes in a full-sib family of Norway spruce. The broad sense heritability was found to be 0.11 for fungal growth. A shift in the pathway connecting primary and secondary metabolism, as detected by a transcriptional switch of DAHP homologues, following H. annosum s.l. inoculation, indicate a possible allocation of more carbon to the secondary metabolism. We also found a consistent induction of the phenylpropanoid pathway and there was an association between the phenol profile and level of resistance. For example, the level of the flavonoid (+)-catechin showed temporal variation in genotypes with higher level of resistance. Matching changes was found in the transcriptome. The R2R3-transcription factor PaTT2-like gene, a putative regulator of flavonoid production, was found to be induced by jasmonic acid in bark. The responses to H. annosum s.l. have been shown to be non-specific but that the magnitude of the response is higher than with other types of challenges. A simultaneous up-regulation of genes related to the salicylic acid- and jasmonic acid-signalling pathway in response to fungal inoculation revealed a closer relationship between the pathways than has been observed in many angiosperms. Finally, the clonal variation in transcriptional and chemical responses observed in this thesis demonstrates variation between genotypes that can be related to different levels of susceptibility to H. annosum s.l. and which can be explored for improvement in coniferous trees. It also demonstrates some of the potential of using modern molecular methods in the breeding practices. Keywords: Picea abies, Heterobasidion, defence, transcript profiling, salicylic acid, jasmonic acid, phenylpropanoid pathway, flavonoids.
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| 2. |
- Arnerup Christiansson, Jenny, et al.
(author)
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The primary module in Norway spruce defence signalling against H. annosum s.l. seems to be jasmonate-mediated signalling without antagonism of salicylate-mediated signalling
- 2013
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In: Planta. - : Springer Science and Business Media LLC. - 0032-0935 .- 1432-2048. ; 237, s. 1037-1045
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Journal article (peer-reviewed)abstract
- A key tree species for the forest industry in Europe is Norway spruce [Picea abies (L.) Karst.]. One of its major diseases is stem and butt rot caused by Heterobasidion parviporum (Fr.) Niemelä & Korhonen, which causes extensive revenue losses every year. In this study, we investigated the parallel induction of Norway spruce genes presumably associated with salicylic acid- and jasmonic acid/ethylene-mediated signalling pathways previously observed in response to H. parviporum. Relative gene expression levels in bark samples of genes involved in the salicylic acid- and jasmonic acid/ethylene-mediated signalling pathways after wounding and inoculation with either the saprotrophic biocontrol fungus Phlebiopsis gigantea or with H. parviporum were analysed with quantitative PCR at the site of the wound and at two distal locations from the wound/inoculation site to evaluate their roles in the induced defence response to H. parviporum in Norway spruce. Treatment of Norway spruce seedlings with methylsalicylate, methyljasmonate and inhibitors of the jasmonic acid/ethylene signalling pathway, as well as the Phenylalanine ammonia lyase inhibitor 2-aminoindan-2-phosphonic acid were conducted to determine the responsiveness of genes characteristic of the different pathways to different hormonal stimuli. The data suggest that jasmonic acid-mediated signalling plays a central role in the induction of the genes analysed in this study irrespective of their responsiveness to salicylic acid. This may suggest that jasmonic acid-mediated signalling is the prioritized module in the Norway spruce defence signalling network against H. parviporum and that there seems to be no immediate antagonism between the modules in this interaction.
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| 3. |
- Arnerup, Jenny, et al.
(author)
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The pathogenic white-rot fungus Heterobasidion parviporum triggers non-specific defence responses in the bark of Norway spruce
- 2011
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In: Tree Physiology. - : Oxford University Press. - 0829-318X .- 1758-4469. ; 31:11, s. 1262-1272
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Journal article (peer-reviewed)abstract
- Norway spruce [Picea abies (L.) Karst.] is one of the economically most important conifer species in Europe. The major pathogen on Norway spruce is Heterobasidion parviporum (Fr.) Niemelä & Korhonen. To achieve a better understanding of Norway spruce's defence mechanisms, transcriptional responses in bark to H. parviporum infection were compared with the response to wounding using cDNA-amplified fragment length polymorphism. The majority of the recovered transcript-derived fragments (TDFs) showed a similar expression pattern for infection and wounding treatment, although inoculated samples showed an enhanced reaction. Genes related to systemic acquired resistance, e.g., PR1, accumulated after H. parviporum infection. Simultaneously, several transcripts involved in various aspects of jasmonic acid (JA)- and ethylene (ET)-mediated signalling accumulated. Genes involved in the ubiquitin/proteasome system were also regulated. Expression patterns have been confirmed by quantitative polymerase chain reaction. The expression patterns of the isolated TDFs suggest that infection with H. parviporum in Norway spruce induces a broad defence, with many similarities to non-specific defence responses in angiosperms. The parallel induction of salicylic acid- and JA/ET-mediated pathways implies spatially separated responses in different cell layers, with and without hyphal contact. A set of TDFs were analysed in an independent experiment with unrelated material treated with wounding or with inoculation with H. parviporum or Phlebiopsis gigantea, verifying the original observations and underlining the non-specific defence responses. In addition, our data suggest that rerouting of carbon in secondary metabolism is an integral part of Norway spruce induced defence. We report the sequences of three 3-deoxy-d-arabino-heptulosonate 7-phosphate synthase genes (PaDAHP1, PaDAHP2 and PaDAHP3) and their relative expression in response to wounding and infection with H. parviporum and P. gigantea. The results clearly indicate differential regulation of the three DAHPs in the induced defence responses in Norway spruce. This study gives insights into the central mechanisms in the induced defences in Norway spruce.
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| 4. |
- Arnerup, Jenny, et al.
(author)
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Variation in growth of Heterobasidion parviporum in a full-sib family of Picea abies
- 2010
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In: Scandinavian Journal of Forest Research. - : Taylor & Francis. - 0282-7581 .- 1651-1891. ; 25:2, s. 106-110
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Journal article (peer-reviewed)abstract
- Heterobasidion parviporum (Fr.) Niemelä & Korhonen and Heterobasidion annosum (Fr.) Bref. sensu lato are some of the major forest pathogens in the northern hemisphere causing root and butt rot to conifers. The relative susceptibility to H. parviporum was investigated in a full-sib family of Norway spruce [Picea abies (L.) Karst.] by inoculating a set of 252 cloned progenies from a controlled cross. Four ramets of each progeny were used and the 2-year-old rooted cuttings were incubated for 6 weeks under greenhouse conditions. The condition of the cuttings was assessed visually and all the plants were in excellent vigour with no mortality recorded during the experiment. To score the relative susceptibility, lesion length in the inner bark and fungal growth in the sapwood were measured. Among the progenies, significant differences were found for fungal growth in the sapwood (p<0.0005). There was no significant difference for lesion length; however, there was a significant positive correlation between fungal growth and lesion length. The broad-sense heritability was 0.11 for fungal growth. This shows that the genetic component for susceptibility to H. parviporum can be detected even within a full-sib family of Norway spruce and that there is a potential for mapping quantitative trait loci for this trait in Norway spruce.
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| 5. |
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| 6. |
- Danielsson, Marie, et al.
(author)
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Chemical and transcriptional responses of Norway spruce genotypes with different susceptibility to Heterobasidion spp. infection
- 2011
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In: BMC Plant Biology. - : BioMed Central (BMC). - 1471-2229. ; 11:1
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Journal article (peer-reviewed)abstract
- Background: Norway spruce [Picea abies (L.) Karst.] is one of the most important conifer species in Europe. The wood is economically important and infections by wood-rotting fungi cause substantial losses to the industry. The first line of defence in a Norway spruce tree is the bark. It is a very efficient barrier against infection based on its mechanical and chemical properties. Once an injury or an infection is recognized by the tree, induced defences are activated. In this study we examined transcriptional response, using 454-sequencing, and chemical profiles in bark of Norway spruce trees with different susceptibility to Heterobasidion annosum s.l. infection. The aim was to find associations between the transcriptome and chemical profiles to the level of susceptibility to Heterobasidion spp. in Norway spruce genotypes.Results: Both terpene and phenol compositions were analysed and at 28 days post inoculation (dpi) high levels of 3-carene was produced in response to H. annosum. However, significant patterns relating to inoculation or to genotypes with higher or lower susceptibility could only be found in the phenol fraction. The levels of the flavonoid catechin, which is polymerized into proanthocyanidins (PA), showed a temporal variation; it accumulated between 5 and 15 dpi in response to H. annosum infection in the less susceptible genotypes. The transcriptome data suggested that the accumulation of free catechin was preceded by an induction of genes in the flavonoid and PA biosynthesis pathway such as leucoanthocyanidin reductase. Quantitative PCR analyses verified the induction of genes in the phenylpropanoid and flavonoid pathway. The qPCR data also highlighted genotype-dependent differences in the transcriptional regulation of these pathways.Conclusions: The varying dynamics in transcriptional and chemical patterns displayed by the less susceptible genotypes suggest that there is a genotypic variation in successful spruce defence strategies against Heterobasidion. However, both high levels of piceasides and flavonoids in the less susceptible genotypes suggested the importance of the phenolic compounds in the defence. Clearly an extended comparison of the transcriptional responses in the interaction with Heterobasidion between several independent genotypes exhibiting reduced susceptibility is needed to catalogue mechanisms of successful host defence strategies.
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