| 1. |
- Adomas, Aleksandra, et al.
(författare)
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Comparative analysis of transcript abundance in Pinus sylvestris after challenge with a saprotrophic, pathogenic or mutualistic fungus
- 2008
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Ingår i: Tree Physiology. - : Oxford University Press (OUP). - 0829-318X .- 1758-4469. ; 28:6, s. 885-897
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Tidskriftsartikel (refereegranskat)abstract
- To investigate functional differences in the recognition and response mechanisms of conifer roots to fungi with different trophic strategies, Pinus sylvestris L. was challenged with a saprotrophic fungus Trichoderma aureoviride Rifai. The results were compared with separate studies investigating pine interactions with a pathogen, Heterobasidion annosum (Fr.) Bref. sensu stricto and an ectomycorrhizal symbiont, Laccaria bicolor Maire (Orton). Global changes in the expression of 2109 conifer genes were assayed 1, 5 and 15 days after inoculation. Gene expression data from a cDNA microarray were analyzed by the 2-interconnected mixed linear model statistical approach. The total number of genes differentially expressed compared with the uninfected control was similar after challenge with the pathogen and the ectomycorrhizal symbiont, but the number of differentially expressed genes increased over time, for H. annosum, and decreased for L. bicolor. Inoculation of pine roots with T aureoviride resulted overall in a much lower number of genes with changed transcript levels compared with inoculation with H. annosum or L. bicolor. Functional classification of the differentially expressed genes revealed that the ectomycorrhizal fungus triggered transient induction of defence-related genes. The response and induction of defence against the pathogen was delayed and the magnitude increased over time. Thus, there were specific transcriptional responses depending on whether the conifer roots were challenged with mutualistic, saprotrophic or pathogenic fungi. This suggests that pine trees are able to recognize diverse fungal species and specifically distinguish whether they are pathogenic, neutral or beneficial microbial agents.
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| 2. |
- Ahonen-Jonnarth, Ulla, et al.
(författare)
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Growth and nutrient uptake of ectomycorrhizal Pinus sylvestris seedlings treated with elevated Al concentrations and decreased levels of base cations
- 2003
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Ingår i: Tree Physiology. - : Oxford University Press (OUP). - 0829-318X .- 1758-4469. ; 23:3, s. 157-167
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Tidskriftsartikel (refereegranskat)abstract
- Models of the effects of elevated concentrations of aluminum (Al) on growth and nutrient uptake of forest trees frequently ignore the effects of mycorrhizal fungi. In this study, we present novel data indicating that ectomycorrhizal mycelia may prevent leaching of base cations and Al. Mycorrhizal and non-mycorrhizal Pinus sylvestris L. seedlings were grown in sand obtained from the B-horizon of a local forest. In Experiment 1, non-mycorrhizal seedlings and seedlings inoculated with Hebeloma cf. longicaudum (Pers.: Fr.) Kumm. ss. Lange or Laccaria bicolor (Maire) Orton were provided with nutrient solution containing 2.5 mM Al. Aluminum did not affect growth of non-mycorrhizal seedlings or seedlings inoculated with L. bicolor. Seedlings colonized by H. cf. longicaudum had the highest biomass production of all seedlings grown without added Al, but the fungus did not tolerate Al. Shoots of seedlings colonized by L. bicolor had the lowest nitrogen (N) concentrations but the highest phosphorus (P) concentrations of all seedlings. The treatments had small but significant effects on shoot and root Al concentrations. In Experiment 2, inoculation with L. bicolor was factorially combined with the addition of a complete nutrient solution, or a solution lacking the base cations K, Ca and Mg, and solutions containing 0 or 0.74 mM Al. Seedling growth decreased in response to 0.74 mM Al, but the effect was significant only for non-mycorrhizal seedlings. Mycorrhizal seedlings generally had higher P concentrations than non-mycorrhizal seedlings. Aluminum reduced P uptake in non-mycorrhizal plants but had no effect on P uptake in mycorrhizal plants. Mycorrhizal colonization increased the pH of the soil solution by about 0.5 units and addition of Al decreased the pH by the same amount. We conclude that the presence of ectomycorrhizal mycelia decreased leaching of base cations and Al from the soil.
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| 3. |
- Arnerup, Jenny, et al.
(författare)
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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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Ingår i: Tree Physiology. - : Oxford University Press. - 0829-318X .- 1758-4469. ; 31:11, s. 1262-1272
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Tidskriftsartikel (refereegranskat)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. |
- Asiegbu, Frederick
(författare)
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Response of living tissues of Pinus sylvestris to the saprotrophic biocontrol fungus Phlebiopsis gigantea
- 2011
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Ingår i: Tree Physiology. - : Oxford University Press (OUP). - 0829-318X .- 1758-4469. ; 31, s. 438-451
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Tidskriftsartikel (refereegranskat)abstract
- The saprotrophic fungus Phlebiopsis gigantea has been used for several years as a biocontrol agent against the conifer pathogen Heterobasidion annosum. Although the effectiveness of P. gigantea in biocontrol has been shown empirically, the long-term effect on living conifer trees as well as the mechanism underlying its antagonistic activity is still unknown. An additional concern is the potential of P. gigantea to acquire a necrotrophic habit through adaptation to living wood tissues. By using a combination of histochemical, molecular and transcript profiling (454 sequencing), we investigated under in vitro conditions the necrotrophic capability of P. gigantea and induced localized resistance as a mechanism for its biocontrol action. Pinus sylvestris seedlings (10 years old) were challenged on the xylem surface with P. gigantea or H. annosum. Both fungi provoked strong necrotic lesions, but after prolonged incubation, P. gigantea lesions shrank and ceased to expand further. Tree seedlings pre-treated with P. gigantea further restricted H. annosum-induced necrosis and had more lignified cells. The 454 sequencing revealed elevated transcript levels of genes important for lignification, cell death regulation and jasmonic acid signalling. The results suggest that induced localized resistance is a contributory factor for the biocontrol efficacy of P. gigantea, and it has a limited necrotrophic capability compared with H. annosum.
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| 5. |
- Aye, Tin Nwe, 1989-, et al.
(författare)
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Prediction of tree sapwood and heartwood profiles using pipe model and branch thinning theory
- 2022
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Ingår i: Tree Physiology. - : Oxford University Press. - 0829-318X .- 1758-4469. ; 42:11, s. 2174-2185
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Tidskriftsartikel (refereegranskat)abstract
- Estimates of tree heartwood and sapwood profiles are important in the pulp industry and for dynamic vegetation models, in which they determine tree biomechanical stability and hydraulic conductivity. Several phenomenological models of stem profiles have been developed for this purpose, based on assumptions on how tree crown and foliage distributions change over time. Here, we derive estimates of tree profiles by synthesizing a simple pipe model theory of plant form with a recently developed theory of branch thinning that from simple assumptions quantifies discarded branches and leaves. This allows us to develop a new trunk model of tree profiles from breast height up to the top of the tree. We postulate that leaves that are currently on the tree are connected by sapwood pipes, while pipes that previously connected discarded leaves or branches form the heartwood. By assuming that a fixed fraction of all pipes remain on the trunk after a branching event, as the trunk is traversed from the root system to the tips, this allows us to quantify trunk heartwood and sapwood profiles. We test the trunk model performance on empirical data from five tree species across three continents. We find that the trunk model accurately describes heartwood and sapwood profiles of all tested tree species (calibration; R2: 84-99%). Furthermore, once calibrated to a tree species, the trunk model predicts heartwood and sapwood profiles of conspecific trees in similar growing environments based only on the age and height of a tree (cross-validation/prediction; R2: 68-98%). The fewer and often contrasting parameters needed for the trunk model make it a potentially useful complementary tool for biologists and foresters.
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| 6. |
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| 7. |
- Bizjak, Tinkara, et al.
(författare)
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Presence and activity of nitrogen-fixing bacteria in Scots pine needles in a boreal forest : a nitrogen-addition experiment
- 2023
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Ingår i: Tree Physiology. - : Oxford University Press. - 0829-318X .- 1758-4469. ; 43:8, s. 1354-1364
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Tidskriftsartikel (refereegranskat)abstract
- Endophytic nitrogen-fixing bacteria have been detected and isolated from the needles of conifer trees growing in North American boreal forests. Because boreal forests are nutrient-limited, these bacteria could provide an important source of nitrogen for tree species. This study aimed to determine their presence and activity in a Scandinavian boreal forest, using immunodetection of nitrogenase enzyme subunits and acetylene-reduction assays of native Scots pine (Pinus sylvestris L.) needles. The presence and rate of nitrogen fixation by endophytic bacteria were compared between control plots and fertilized plots in a nitrogen-addition experiment. In contrast to the expectation that nitrogen-fixation rates would decline in fertilized plots, as seen, for instance, with nitrogen-fixing bacteria associated with bryophytes, there was no difference in the presence or activity of nitrogen-fixing bacteria between the two treatments. The extrapolated calculated rate of nitrogen fixation relevant for the forest stand was 20 g N ha-1 year-1, which is rather low compared with Scots pine annual nitrogen use but could be important for the nitrogen-poor forest in the long term. In addition, of 13 colonies of potential nitrogen-fixing bacteria isolated from the needles on nitrogen-free media, 10 showed in vitro nitrogen fixation. In summary, 16S rRNA sequencing identified the species as belonging to the genera Bacillus, Variovorax, Novosphingobium, Sphingomonas, Microbacterium and Priestia, which was confirmed by Illumina whole-genome sequencing. Our results confirm the presence of endophytic nitrogen-fixing bacteria in Scots pine needles and suggest that they could be important for the long-term nitrogen budget of the Scandinavian boreal forest.
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| 8. |
- Brum, Mauro, et al.
(författare)
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Ecophysiological controls on water use of tropical cloud forest trees in response to experimental drought
- 2023
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Ingår i: Tree Physiology. - : Oxford University Press. - 0829-318X .- 1758-4469. ; 43:9, s. 1514-1532
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Tidskriftsartikel (refereegranskat)abstract
- Tropical montane cloud forests (TMCFs) are expected to experience more frequent and prolonged droughts over the coming century, yet understanding of TCMF tree responses to moisture stress remains weak compared with the lowland tropics. We simulated a severe drought in a throughfall reduction experiment (TFR) for 2 years in a Peruvian TCMF and evaluated the physiological responses of several dominant species (Clusia flaviflora Engl., Weinmannia bangii (Rusby) Engl., Weinmannia crassifolia Ruiz & Pav. and Prunus integrifolia (C. Presl) Walp). Measurements were taken of (i) sap flow; (ii) diurnal cycles of stem shrinkage, stem moisture variation and water-use; and (iii) intrinsic water-use efficiency (iWUE) estimated from foliar δ13C. In W. bangii, we used dendrometers and volumetric water content (VWC) sensors to quantify daily cycles of stem water storage. In 2 years of sap flow (Js) data, we found a threshold response of water use to vapor pressure deficit vapor pressure deficit (VPD) > 1.07 kPa independent of treatment, though control trees used more soil water than the treatment trees. The daily decline in water use in the TFR trees was associated with a strong reduction in both morning and afternoon Js rates at a given VPD. Soil moisture also affected the hysteresis strength between Js and VPD. Reduced hysteresis under moisture stress implies that TMCFs are strongly dependent on shallow soil water. Additionally, we suggest that hysteresis can serve as a sensitive indicator of environmental constraints on plant function. Finally, 6 months into the experiment, the TFR treatment significantly increased iWUE in all study species. Our results highlight the conservative behavior of TMCF tree water use under severe soil drought and elucidate physiological thresholds related to VPD and its interaction with soil moisture. The observed strongly isohydric response likely incurs a cost to the carbon balance of the tree and reduces overall ecosystem carbon uptake.
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| 9. |
- Businge, Edward, et al.
(författare)
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A possible biochemical basis for fructose-induced inhibition of embryo development in Norway spruce (Picea abies)
- 2014
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Ingår i: Tree Physiology. - : Oxford University Press (OUP). - 0829-318X .- 1758-4469. ; 34, s. 657-669
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Tidskriftsartikel (refereegranskat)abstract
- Sugars play an important role in various physiological processes during plant growth and development; however, the developmental roles and regulatory functions of hexoses other than glucose are still largely unclear. Recent studies suggest that blocked embryo development in Norway spruce (Picea abies (L.) Karst) is associated with accumulation of fructose. In the present study, the potential biochemical regulatory mechanism of glucose and fructose was studied during development of somatic embryos of Norway spruce from pro-embryogenic masses to mature embryos. The changes in protein fluorescence, a marker of the Maillard reaction, were monitored in two cell lines of Norway spruce that were grown on media containing sucrose (control), glucose or fructose. Manual time-lapse photography showed that growth of embryogenic cultures on medium containing sucrose was characterized by normal development of mature embryos whereas the embryogenic cultures that were grown on media containing glucose or fructose did not develop mature embryos. The biochemical analyses of embryogenic samples collected during embryo development showed that: (i) the content of glucose and fructose in the embryogenic cultures increased significantly during growth on each medium, respectively; (ii) the accumulation of Maillard products in the embryogenic cultures was highly correlated with the endogenous content of fructose but not glucose; and (iii) the embryogenic cultures grown on fructose displayed the highest protein carbonyl content and DNA damage whereas the highest content of glutathione was recorded in the embryogenic cultures that had grown on sucrose. Our data suggest that blocked development of embryos in the presence of fructose may be associated with the Maillard reaction.
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| 10. |
- Businge, Edward, et al.
(författare)
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Metabolite profiling reveals clear metabolic changes during somatic embryo development of Norway spruce (Picea abies)
- 2012
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Ingår i: Tree Physiology. - : Oxford University Press (OUP). - 0829-318X .- 1758-4469. ; 32, s. 232-244
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Tidskriftsartikel (refereegranskat)abstract
- Progress on industrial-scale propagation of conifers by somatic embryogenesis has been hampered by the differences in developmental capabilities between cell lines, which are limiting the capture of genetic gains from breeding programs. In this study, we investigated the metabolic events occurring during somatic embryo development in Norway spruce to establish a better understanding of the fundamental metabolic events required for somatic embryo development. Three embryogenic cell lines of Norway spruce (Picea abies (L.) Karst) with different developmental capabilities were studied during somatic embryo development from proliferation of proembryogenic masses to mature somatic embryos. The three different cell lines displayed normal, aberrant and blocked somatic embryo development. Metabolite profiles from four development stages in each of the cell lines were obtained using combined gas chromatography-mass spectrometry. Multivariate discriminant analyses of the metabolic data revealed significant metabolites (P < 0.05) for each development stage and transition. The results suggest that endogenous auxin and sugar signaling affects initial stages of somatic embryo development. Furthermore, the results highlight the importance of a timed stress response and the presence of stimulatory metabolites during late stages of embryo development.
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