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Norway spruce ( Picea abies [L.] Karst.) is a broadly distributed European conifer tree whose history has been intensively studied by means of fossil records to infer the location of full-glacial refugia and the main routes of postglacial colonization. Here we use recently compiled fossil pollen data as a template to examine how past demographic events have influenced the species’ modern genetic diversity. Variation was assessed in the mitochondrial nad1 gene containing two minisatellite regions. Among the 369 populations (4876 trees) assayed, 28 mitochondrial variants were identified. The patterns of population subdivision superimposed on interpolated fossil pollen distributions indicate that survival in separate refugia and postglacial colonization has led to significant structuring of genetic variation in the southern range of the species. The populations in the northern range, on the other hand, showed a shallow genetic structure consistent with the fossil pollen data, suggesting that the vast northern range was colonized from a single refugium. Although the genetic diversity decreased away from the putative refugia, there were large differences between different colonization routes. In the Alps, the diversity decreased over short distances, probably as a result of population bottlenecks caused by the presence of competing tree species. In northern Europe, the diversity was maintained across large areas, corroborating fossil pollen data in suggesting that colonization took place at high population densities. The genetic diversity increased north of the Carpathians, probably as a result of admixture of expanding populations from two separate refugia. [ABSTRACT FROM AUTHOR]

Cold deacclimation and preparation to flushing likely requires rehydration of meristems. Therefore, water stress related genes, such as dehydrins (DHN), might play an important role in providing protection during winter dormancy, deacclimation and bud burst timing processes. Here we report the sequence analysis of several Norway spruce DHN identified in late and early flushing suppressive subtraction hybridization cDNA libraries and in our Norway spruce EST database. We obtained 15 cDNAs, representing eight genes from three distinct types of DHN, and studied differential expression of these genes before and during bud burst in spring, using qRT-PCR. We found the visible reduction in transcript level of most DHN towards the bud burst, supported by a significant down-regulation of the DHN in needles during experimental induction of bud burst applied at three time points during autumn in Norway spruce grafts. For most of the DHN transcripts, their expression levels in late-flushing spruces were significantly higher than in the early flushing ones at the same calendar dates but were remarkably similar at the same bud developmental stage. From our results we may conclude that the difference between the early and the late families is in timing of the molecular processes leading to bud burst due to differences in their response to the increasing temperature in the spring. They are induced much earlier in the early flushing families. [ABSTRACT FROM AUTHOR]

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The temperature during maternal reproduction affects adaptive traits in progenies of Norway spruce ( Picea abies (L) Karst.). Seed production in a cold environment advances bud set and cold acclimation in the autumn and dehardening and flushing in spring, whereas a warm reproductive environment delays timing of these traits. We repeated crosses between the same parents and produced seeds under contrasting temperatures. Elevated temperatures were applied at different time points from female meiosis to embryogenesis, followed by full-sib progeny tests in common environments. We measured timing of terminal bud formation, cold acclimation in the autumn and transcription levels of conifer phytochromes PhyO, PhyN, PhyP, and the class IV chitinase PaChi4 in these tests. No progeny differences were found that could be related to temperature differences during prezygotic stages and fertilization. In contrast, progeny performance was strongly associated with the degree-days from proembryo to mature seeds. Progenies with a warm embryonic history formed terminal buds later, were less hardy and expressed lower transcription levels of the Phy and PaChi4 genes. We hypothesize that temperature during zygotic embryogenesis and seed maturation regulates an ‘epigenetic memory’ in the progeny, involving differential expression of genes that may regulate bud phenology, cold acclimation and embryogenesis in Norway spruce. [ABSTRACT FROM AUTHOR]

Plant growth and adaptation to cold and freezing temperatures in a CO2-enriched atmosphere have received little attention despite their predicted effects on plant distribution and productivity. In this study we looked at the interaction between elevated CO2 and development of freezing tolerance in Norway spruce (Picea abies (L.) Karst.). First-year seedlings were grown under controlled conditions in an atmosphere enriched in CO2 (70 Pa) for one simulated growth season. We measured shoot growth, registered the timing of growth cessation and bud set, measured needle net photosynthetic rate, and determined needle carbohydrate concentration (fructose+pinitol, glucose, sucrose, inositol, raffinose and starch). Freezing tolerance (LT50) was determined after exposing whole seedlings to temperatures ranging from -6.5 to -36.0°C and scoring for visual needle browning. Elevated CO2 did not affect height growth or the timing of growth cessation and bud set. The only statistically significant effects of CO2 treatment were on seedling dry weight, percent dry matter and starch content. During the three weeks after growth cessation and bud set, freezing tolerance increased from -10 to -35°C, and there was a marked increase in all soluble sugars except inositol. However, neither freezing tolerance nor the concentration of soluble sugars was significantly influenced by elevated CO2. [ABSTRACT FROM AUTHOR]

Abstract: Local- and systemic-induced defense responses were investigated in the Norway spruce–Rhizoctonia sp. pathosystem and compared with drought alone or a combination of the two stresses using real-time reverse transcription (RT)-PCR. The compatible pathogen stress resulted in a transient systemic induction of selected defense-related gene transcripts in the shoot and a persistent local induction in the roots. Drought led to a similar but delayed host response, while the combined stress gave larger and earlier changes in transcripts than for the two stresses separately. Thus, distinguishing between the effect of a root infection and drought based on systemic transcription patterns may be feasible especially when the temporal expression patterns are closely monitored. [Copyright &y& Elsevier]

Abstract: Expression of selected genes in needles of Norway spruce (Picea abies [L.] Karst) was investigated by following their transcription levels during late autumn. Transcription was assessed in mature needles which likely serve as sensor of environmental cues that enable trees in the temperate and boreal regions to change between stages of growth, frost tolerance and bud dormancy. Samples were collected from grafts kept under outdoor conditions and after bud burst forcing in greenhouse at 20 °C (12 h darkness) for one week. Transcription was assayed with real-time RT-PCR. During the sampling period, chilling requirement was partially fulfilled, and time to bud burst after forcing was decreased. Of the 27 transcripts studied, expression of 16 was significantly affected either by forcing, sampling time, or interaction between them. PaSAP, PaACP, PaSGS3, PaWRKY, PaDIR9, PaCCCH and dehydrin genes responded drastically to forcing temperatures at all sampling points, showing no correlation with readiness for bud burst. Expression patterns of some vernalization pathway gene homologs PaVIN3, and also of PaMDC, PaLOV1 and PaDAL3 had a clear opposite trends between forcing and outdoor conditions, which could imply their role in chilling accumulation and bud burst regulation/cold acclimation. These genes could constitute putative candidates for further detailed study, whose regulation in needles may be involved in preparation towards bud burst and chilling accumulation sensing. [Copyright &y& Elsevier]