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排序方式: 共有224条查询结果,搜索用时 328 毫秒
61.
Juan A. Martín Johanna Witzell Kathrin Blumenstein Elzbieta Rozpedowska Marjo Helander Thomas N. Sieber Luis Gil 《PloS one》2013,8(2)
Efforts to introduce pathogen resistance into landscape tree species by breeding may have unintended consequences for fungal diversity. To address this issue, we compared the frequency and diversity of endophytic fungi and defensive phenolic metabolites in elm (Ulmus spp.) trees with genotypes known to differ in resistance to Dutch elm disease. Our results indicate that resistant U. minor and U. pumila genotypes exhibit a lower frequency and diversity of fungal endophytes in the xylem than susceptible U. minor genotypes. However, resistant and susceptible genotypes showed a similar frequency and diversity of endophytes in the leaves and bark. The resistant and susceptible genotypes could be discriminated on the basis of the phenolic profile of the xylem, but not on basis of phenolics in the leaves or bark. As the Dutch elm disease pathogen develops within xylem tissues, the defensive chemistry of resistant elm genotypes thus appears to be one of the factors that may limit colonization by both the pathogen and endophytes. We discuss a potential trade-off between the benefits of breeding resistance into tree species, versus concomitant losses of fungal endophytes and the ecosystem services they provide. 相似文献
62.
Teemu Natunen Henna Martiskainen Timo Saraj?rvi Seppo Helisalmi Juha-Pekka Pursiheimo Jayashree Viswanathan Marjo Laitinen Petra M?kinen Tarja Kauppinen Tuomas Rauramaa Ville Leinonen Irina Alafuzoff Annakaisa Haapasalo Hilkka Soininen Mikko Hiltunen 《PloS one》2013,8(11)
Alzheimer''s disease (AD) has been postulated to involve defects in the clearance of amyloid-β (Aβ). Activation of liver X receptor α (LXRα) increases the expression of apolipoprotein E (ApoE) as well as cholesterol transporters ABCA1 and ABCG1, leading to augmented clearance of Aβ. We have previously shown that the C allele of rs7120118 in the NR1H3 gene encoding LXRα reduces the risk of AD. Here, we wanted to assess whether the rs7120118 variation affects the progression of AD and modulates the expression of NR1H3 and its downstream targets APOE, ABCA1 and ABCG1.We utilized tissue samples from the inferior temporal cortex of 87 subjects, which were subdivided according to Braak staging into mild, moderate and severe AD groups on the basis of AD-related neurofibrillary pathology. APOE ε4 allele increased soluble Aβ42 levels in the tissue samples in a dose-dependent manner, but did not affect the expression status of APOE. In contrast, the CC genotype of rs7120118 was underrepresented in the severe group, although this result did not reach statistical significance. Also, patients with the CC genotype of rs7120118 showed significantly decreased soluble Aβ42 levels as compared to the patients with TT genotype. Although the severity of AD did not affect NR1H3 expression, the mRNA levels of NR1H3 among the patients with CT genotype of rs7120118 were significantly increased as compared to the patients with TT genotype. These results suggest that genetic variation in NR1H3 modulates the expression of LXRα and the levels of soluble Aβ42. 相似文献
63.
Jari HeikkinenMaija Risteli Outi LampelaPaula Alavesa Marjo KarppinenAndré H. Juffer Raili Myllylä 《Matrix biology》2011,30(1):27-33
Lysyl hydroxylases (LH), which catalyze the post-translational modifications of lysines in collagen and collagen-like proteins, function as dimers. However, the amino acids responsible for dimerization and the role of dimer formation in the enzymatic activities of LH have not yet been identified. We have localized the region responsible for the dimerization of lysyl hydroxylase 3 (LH3), a multifunctional enzyme of collagen biosynthesis, to a sequence of amino acids between the glycosyltransferase activity and the lysyl hydroxylase activity domains. This area is covered by amino acids 541-547 in human LH3, but contains no cysteine residues. The region is highly conserved among LH isoforms, and is also involved in the dimerization of LH1 subunits. Dimerization is required for the LH activity of LH3, whereas it is not obligatory for the glycosyltransferase activities. In order to determine whether complex formation can occur between LH molecules originating from different species, and between different LH isoforms, double expressions were generated in a baculovirus system. Heterocomplex formation between mouse and human LH3, between human LH1 and LH3 and between human LH2 and LH3 was detected by western blot analyses. However, due to the low amount of complexes formed, the in vivo function of heterocomplexes remains unclear. 相似文献
64.
Tuomainen M Ahonen V Kärenlampi SO Schat H Paasela T Svanys A Tuohimetsä S Peräniemi S Tervahauta A 《Planta》2011,233(6):1173-1184
Stress tolerance is currently one of the major research topics in plant biology because of the challenges posed by changing
climate and increasing demand to grow crop plants in marginal soils. Increased Zn tolerance and accumulation has been reported
in tobacco expressing the glyoxalase 1-encoding gene from Brassica juncea. Previous studies in our laboratory showed some Zn tolerance-correlated differences in the levels of glyoxalase 1-like protein
among accessions of Zn hyperaccumulator Thlaspi caerulescens. We have now isolated the corresponding gene (named here TcGLX1), including ca. 570 bp of core and proximal promoter region. The predicted protein contains three glyoxalase 1 motifs and several putative
sites for post-translational modification. In silico analysis predicted a number of cis-acting elements related to stress. The expression of TcGLX1 was not responsive to Zn. There was no correlation between the levels of TcGLX1 expression and the degrees of Zn tolerance or accumulation among T. caerulescens accessions nor was there co-segregation of TcGLX1 expression with Zn tolerance or Zn accumulation among F3 lines derived from crosses between plants from accessions with contrasting
phenotypes for these properties. No phenotype was observed in an A. thaliana T-DNA insertion line for the closest A. thaliana homolog of TcGLX1, ATGLX1. These results suggest that glyoxalase 1 or at least the particular isoform studied here is not a major determinant of Zn
tolerance in the Zn hyperaccumulator plant T. caerulescens. In addition, ATGLX1 is not essential for normal Zn tolerance in the non-tolerant, non-accumulator plant A. thaliana. Possible explanations for the apparent discrepancy between this and previous studies are discussed. 相似文献
65.
Degenhardt T Saramäki A Malinen M Rieck M Väisänen S Huotari A Herzig KH Müller R Carlberg C 《Journal of molecular biology》2007,372(2):341-355
The nuclear receptors peroxisome proliferator-activated receptors (PPARs) are known for their critical role in the metabolic syndrome. Here, we show that they are direct regulators of the family of pyruvate dehydrogenase kinase (PDK) genes, whose products act as metabolic homeostats in sensing hunger and satiety levels in key metabolic tissues by modulating the activity of the pyruvate dehydrogenase complex. Mis-regulation of this tightly controlled network may lead to hyperglycemia. In human embryonal kidney cells we found the mRNA expression of PDK2, PDK3 and PDK4 to be under direct primary control of PPAR ligands, and in normal mouse kidney tissue Pdk2 and Pdk4 are PPAR targets. Both, treatment of HEK cells with PPARbeta/delta-specific siRNA and the genetic disruption of the Pparbeta/delta gene in mouse fibroblasts resulted in reduced expression of Pdk genes and abolition of induction by PPARbeta/delta ligands. These findings suggest that PPARbeta/delta is a key regulator of PDK genes, in particular the PDK4/Pdk4 gene. In silico analysis of the human PDK genes revealed two candidate PPAR response elements in the PDK2 gene, five in the PDK3 gene and two in the PDK4 gene, but none in the PDK1 gene. For seven of these sites we could demonstrate both PPARbeta/delta ligand responsiveness in context of their chromatin region and simultaneous association of PPARbeta/delta with its functional partner proteins, such as retinoidXreceptor, co-activator and mediator proteins and phosphorylated RNA polymerase II. In conclusion, PDK2, PDK3 and PDK4 are primary PPARbeta/delta target genes in humans underlining the importance of the receptor in the control of metabolism. 相似文献
66.
Saastamoinen M 《Oecologia》2007,153(3):569-578
Life history theory often assumes a trade-off between dispersal and reproduction, and such a trade-off is commonly observed
in wing-dimorphic insects. The results are less consistent for wing-monomorphic species, for which it is more difficult to
assess dispersal capacity and rate. Three replicate experiments were carried out in consecutive years on the Glanville fritillary
butterfly in a large outdoor population cage to study the relationship between lifetime egg production and mobility. The experimental
material included females originating from newly-established and old populations, as previous studies have shown dispersal
capacity to depend on population age. There was a consistent and significant interaction between mobility and population age,
such that in newly-established populations mobile females had higher fecundity than less mobile females, while in old populations
there was no such relationship. As selection favours individuals with the highest fecundity, selection pressure on mobility
is likely to be different between the two population types, which may contribute to maintenance of variation in dispersal
rate in the metapopulation as a whole. Several other female traits also affected lifetime fecundity, including lifespan, number
of matings and date of eclosion, although these effects were not consistent across the years. These results highlight the
importance of conducting experiments in more than one year before generalizing about patterns in life history variation. 相似文献
67.
Development of ground vegetation biomass and nutrient pools in a clear-cut disc-plowed boreal forest
Marjo Palviainen Leena Finér Ari Laurén Hannu Mannerkoski Sirpa Piirainen Michael Starr 《Plant and Soil》2007,297(1-2):43-52
Nutrient leaching from forest substrate after clear-cutting and subsequent soil preparation is strongly influenced by the
capacity of ground vegetation to sequester the released nutrients. We studied the rates and patterns of biomass and nutrient
accumulation in ground vegetation growing on ridges, in furrows and on undisturbed surfaces for 2–5 years after disc-plowing
in eastern Finland. The biomass of mosses on ridges remained significantly lower than that in furrows and on undisturbed surfaces.
Field layer biomass on ridges and in furrows was significantly lower than on undisturbed surfaces throughout the study period.
Field layer biomass increased more on ridges than in furrows. Root biomass on ridges and undisturbed surfaces was considerably
higher than in furrows. Five years after disc-plowing, total biomass and nutrient pools for ridges (biomass 4,975 kg ha−1, N 40 kg ha−1, P 5 kg ha−1, K 20 kg ha−1 and Ca 18 kg ha−1) and undisturbed surfaces (biomass 5,613 kg ha−1, N 43 kg ha−1, P 5 kg ha−1, K 22 kg ha−1 and Ca 18 kg ha−1) were similar, but considerably lower for furrows (biomass 1,807 kg ha−1, N 16 kg ha−1, P 2 kg ha−1, K 10 kg ha−1 and Ca 6 kg ha−1). Ridges covered 25% of the area, furrows 30 and 45% was undisturbed surfaces. Taking into account the proportion of each
type of surface, values for the whole prepared clear-cut area were 4,312, 34, 4, 18 and 14 kg ha−1 for biomass, N, P, K and Ca, respectively. Biomass and nutrient pools had not returned to uncut forest levels at the end
of the 5-year study period. The results indicate that mosses and field layer vegetation respond differently to soil preparation,
that the development of biomass on ridges, in furrows and on undisturbed surfaces proceeds at different rates, and that the
biomass and nutrient uptake of ground vegetation remains below pre-site preparation levels for several years. However, ridges,
which are known to be the most susceptible to leaching, revegetate rapidly.
Responsible Editor: Tibor Kalapos. 相似文献
68.
Takaluoma K Hyry M Lantto J Sormunen R Bank RA Kivirikko KI Myllyharju J Soininen R 《The Journal of biological chemistry》2007,282(9):6588-6596
We have generated mice with targeted inactivation of the Plod1 gene for lysyl hydroxylase 1 (LH1). Its human mutations cause Ehlers-Danlos syndrome VIA (EDS VIA) characterized by muscular hypotonia, joint laxity, and kyphoscoliosis. The Plod1(-/-) mice are flaccid and have gait abnormalities. About 15% of them died because of aortic rupture and smooth muscle cells in non-ruptured Plod1(-/-) aortas showed degenerative changes. Collagen fibrils in the Plod1(-/-) aorta and skin had an abnormal morphology. The LH activity level in the Plod1(-/-) skin and aorta samples was 35-45% of that in the wild type. The hydroxylysine content was decreased in all the Plod1(-/-) tissues, ranging from 22% of that in the wild type in the skin to 75 and 86% in the femur and lung. The hydroxylysylpyridinoline crosslinks likewise showed decreases in all the Plod1(-/-) tissues, ranging from 28 and 33% of that in the wild type in the aorta and cornea to 47 and 59% in femur and tendon, while lysylpyridinolines were increased. The hydroxylysines found in the Plod1(-/-) collagens and their cross-links were evidently synthesized by the other two LH isoenzymes. Few data are available on abnormalities in EDS VIA tissues other than the skin. Plod1(-/-) mice offer an in vivo model for systematic analysis of the tissue-specific consequences of the lack of LH1 activity and may also provide a tool for analyzing the roles of connective tissue in muscle function and the complex interactions occurring in the proper assembly of the extracellular matrix. 相似文献
69.
Maria von Crutlein Pivi H. Leinonen Helena Korpelainen Marjo Helander Henry Vre Kari Saikkonen 《Ecology and evolution》2019,9(6):3661-3674
We conducted a large‐scale population genetic survey of genetic diversity of the host grass Festuca rubra s.l., which fitness can be highly dependent on its symbiotic fungus Epichloë festucae, to evaluate genetic variation and population structure across the European range. The 27 studied populations have previously been found to differ in frequencies of occurrence of the symbiotic fungus E. festucae and ploidy levels. As predicted, we found decreased genetic diversity in previously glaciated areas in comparison with nonglaciated regions and discovered three major maternal genetic groups: southern, northeastern, and northwestern Europe. Interestingly, host populations from Greenland were genetically similar to those from the Faroe Islands and Iceland, suggesting gene flow also between those areas. The level of variation among populations within regions is evidently highly dependent on the postglacial colonization history, in particular on the number of independent long‐distance seed colonization events. Yet, also anthropogenic effects may have affected the population structure in F. rubra. We did not observe higher fungal infection rates in grass populations with lower levels of genetic variability. In fact, the fungal infection rates of E. festucae in relation to genetic variability of the host populations varied widely among geographical areas, which indicate differences in population histories due to colonization events and possible costs of systemic fungi in harsh environmental conditions. We found that the plants of different ploidy levels are genetically closely related within geographic areas indicating independent formation of polyploids in different maternal lineages. 相似文献
70.
Guillaume Minard Gleb Tikhonov Otso Ovaskainen Marjo Saastamoinen 《Environmental microbiology》2019,21(11):4253-4269
Understanding of the ecological factors that shape intraspecific variation of insect microbiota in natural populations is relatively poor. In Lepidopteran caterpillars, microbiota is assumed to be mainly composed of transient bacterial symbionts acquired from the host plant. We sampled Glanville fritillary (Melitaea cinxia) caterpillars from natural populations to describe their gut microbiome and to identify potential ecological factors that determine its structure. Our results demonstrate high variability of microbiota composition even among caterpillars that shared the same host plant individual and most likely the same genetic background. We observed that the caterpillars harboured microbial classes that varied among individuals and alternated between two distinct communities (one composed of mainly Enterobacteriaceae and another with more variable microbiota community). Even though the general structure of the microbiota was not attributed to the measured ecological factors, we found that phylogenetically similar microbiota showed corresponding responses to the sex and the parasitoid infection of the caterpillar and to those of the host plant's microbial and chemical composition. Our results indicate high among-individual variability in the microbiota of the M. cinxia caterpillar and contradict previous findings that the host plant is the major driver of the microbiota communities of insect herbivores. 相似文献