Cell Wall Lignin is Polymerised by Class Ⅲ Secretable Plant Peroxidases in Norway Spruce

Class Ⅲ secretable plant peroxidases occur as a large family of genes in plants with many functions and probable redundancy. In this review we are concentrating on the evidence we have on the catalysis of lignin polymerization by class Ⅲ plant peroxidases present in the apoplastic space in the xylem of trees. Some evidence exists on the specificity of peroxidase isozymes in lignin polymerization through substrate specificity studies, from antisense mutants in tobacco and poplar and from tissue and cell cult...     

Mutations in AXIN2 cause familial tooth agenesis and predispose to colorectal cancer

Wnt signaling regulates embryonic pattern formation and morphogenesis of most organs. Aberrations of regulation of Wnt signaling may lead to cancer. Here, we have used positional cloning to identify the causative mutation in a Finnish family in which severe permanent tooth agenesis (oligodontia) and colorectal neoplasia segregate with dominant inheritance. Eleven members of the family lacked at least eight permanent teeth, two of whom developed only three permanent teeth. Colorectal cancer or precancerous lesions of variable types were found in eight of the patients with oligodontia. We show that oligodontia and predisposition to cancer are caused by a nonsense mutation, Arg656Stop, in the Wnt-signaling regulator AXIN2. In addition, we identified a de novo frameshift mutation 1994-1995insG in AXIN2 in an unrelated young patient with severe tooth agenesis. Both mutations are expected to activate Wnt signaling. The results provide the first evidence of the importance of Wnt signaling for the development of dentition in humans and suggest that an intricate control of Wnt-signal activity is necessary for normal tooth development, since both inhibition and stimulation of Wnt signaling may lead to tooth agenesis. Our findings introduce a new gene for hereditary colorectal cancer and suggest that tooth agenesis may be an indicator of cancer susceptibility.     

Ca(2+)-induced high amplitude swelling and cytochrome c release from wheat (Triticum aestivum L.) mitochondria under anoxic stress

Under stress conditions, mitochondria sense metabolic changes, e.g. in pH, cytoplasmic Ca(2+), energy status, and reactive oxygen species (ROS), and respond by induction of the permeability transition pore (PTP) and by releasing cytochrome c, thus initiating the programmed cell death (PCD) cascade in animal cells. In plant cells, the presence of all the components of the cascade has not yet been shown. In wheat (Triticum aestivum L.) root mitochondria, the onset of anoxia caused rapid dissipation of the inner membrane potential, initial shrinkage of the mitochondrial matrix and the release of previously accumulated Ca(2+). Ca(2+) uptake by mitochondria was dependent on the presence of inorganic phosphate. Treatment of mitochondria with high micromolar and millimolar Ca(2+) (but not Mg(2+)) concentrations induced high amplitude swelling, indicative of PTP opening. Alterations in mitochondrial volume were confirmed by transmission electron microscopy. Mitochondrial swelling was not sensitive to cyclosporin A (CsA)-an inhibitor of mammalian PTP. The release of cytochrome c was monitored under lack of oxygen. Anoxia alone failed to induce cytochrome c release from mitochondria. Oxygen deprivation and Ca(2+) ions together caused cytochrome c release in a CsA-insensitive manner. This process correlated positively with Ca(2+) concentration and required Ca(2+) localization in the mitochondrial matrix. Functional characteristics of wheat root mitochondria, such as membrane potential, Ca(2+) transport, swelling, and cytochrome c release under lack of oxygen are discussed in relation to PCD.     

Animal disease models generated by genetic engineering of polyamine metabolism

The polyamines putrescine, spermidine and spermine are natural components of all living cells. Although their exact cellular functions are still largely unknown, a constant supply of these compounds is required for mammalian cell proliferation to occur. Studies with animals displaying genetically altered polyamine metabolism have shown that polyamines are intimately involved in the development of diverse tumors, putrescine apparently has specific role in skin physiology and neuroprotection and the higher polyamines spermidine and spermine are required for the maintenance of pancreatic integrity and liver regeneration. In the absence of ongoing polyamine biosynthesis, murine embryogenesis does not proceed beyond the blastocyst stage. The last years have also witnessed the appearance of the first reports linking genetically altered polyamine metabolism to human diseases.     

Preferences of pollinators and herbivores in gynodioecious Geranium sylvaticum

BACKGROUND AND AIMS: For the maintenance of gynodioecy (i.e. the coexistence of female and hermaphroditic plants), females need to compensate for the lack of pollen production through higher seed production or better progeny quality compared to hermaphrodites. In Geranium sylvaticum, females produce more seeds per flower than hermaphrodites. This difference in seed production might be modified by biological interactions with pollinators and herbivores that may favour one sex and thus affect the maintenance of gynodioecy. METHODS: Sexual dimorphism in flower size and flowering phenology, and in attractiveness to pollinators, pre-dispersal seed predators and floral herbivores were examined in natural populations of G. sylvaticum. KEY RESULTS: Pollinators preferred hermaphrodites 25 % more often than females in two of the three study populations, and floral herbivores attacked hermaphrodites 15 % more often than females in two of the six study populations. These preferences might be explained by the larger flower size of hermaphrodites. In contrast, seed predators did not prefer either sex. CONCLUSIONS: The data suggest that pollinator preference does not benefit females, whereas the higher floral herbivory of hermaphrodites might enhance the maintenance of females in G. sylvaticum. Thus, although the data support the view that ecological factors may contribute to the maintenance of gynodioecy, they also suggest that these contributions may vary across populations and that they may function in opposite directions.     

Xylose chemostat isolates of Saccharomyces cerevisiae show altered metabolite and enzyme levels compared with xylose, glucose, and ethanol metabolism of the original strain

The efficient conversion of xylose-containing biomass hydrolysate by the ethanologenic yeast Saccharomyces cerevisiae to useful chemicals such as ethanol still remains elusive, despite significant efforts in both strain and process development. This study focused on the recovery and characterization of xylose chemostat isolates of a S. cerevisiae strain that overexpresses xylose reductase- and xylitol dehydrogenase-encoding genes from Pichia stipitis and the gene encoding the endogenous xylulokinase. The isolates were recovered from aerobic chemostat cultivations on xylose as the sole or main carbon source. Under aerobic conditions, on minimal medium with 30 g l^–1 xylose, the growth rate of the chemostat isolates was 3-fold higher than that of the original strain (0.15 h^–1 vs 0.05 h^–1). In a detailed characterization comparing the metabolism of the isolates with the metabolism of xylose, glucose, and ethanol in the original strain, the isolates showed improved properties in the assumed bottlenecks of xylose metabolism. The xylose uptake rate was increased almost 2-fold. Activities of the key enzymes in the pentose phosphate pathway (transketolase, transaldolase) increased 2-fold while the concentrations of their substrates (pentose 5-phosphates, sedoheptulose 7-phosphate) decreased correspondingly. Under anaerobic conditions, on minimal medium with 45 g l^–1 xylose, the ethanol productivity (in terms of cell dry weight; CDW) of one of the isolates increased from 0.012 g g^–1 CDW h^–1 to 0.017 g g^–1 CDW h^–1 and the yield from 0.09 g g^–1 xylose to 0.14 g g^–1 xylose, respectively.     

Antioxidant status of anoxia-tolerant and -intolerant plant species under anoxia and reaeration

The redox potential of the cell, as well as the antioxidant status of the tissue, are considered to be important regulatory constituents in an adaptive response in plants. Here the involvement of active antioxidants ascorbic acid (AA), reduced glutathione (GSH) and α - and β -tocopherols in reactive oxygen species scavenging, and the effect of anoxic stress on their reduction state were studied in 4 anoxia-tolerant and -intolerant plant species: Iris germanica L., Iris pseudacorus L., wheat ( Triticum aestivum L. cv. Leningradka) and rice ( Oryza sativa L. cv. VNIIR). The initial antioxidant content (both AA and GSH) was higher in the rhizomes of the more anoxia-tolerant Iris spp., as compared with that of the roots of the cereals. The predominant form of ascorbate was dehydroascorbic acid (DHA) in the cereals and AA in the Iris spp. Imposition of anoxia with subsequent reoxygenation resulted in an overall depletion of the reduced forms of antioxidants. No concurrent increase in oxidised forms (DHA and conjugated glutathione) was observed in anoxic samples. α -tocopherol content in Iris spp. was in the range 1–2 μg g⁻¹ fresh weight, while β -tocopherol content was higher in the anoxia-intolerant I. germanica (7.2 μg g⁻¹ fresh weight) as compared with the tolerant I. pseudacorus (1.5 μg g⁻¹ fresh weight). In I. pseudacorus , a significant decrease in α - and β -tocopherol levels was observed only after long-term (45 days) anoxia. The results suggested exclusion of AA and GSH from the redox cycling under prolonged anoxia, and a concomitant decrease in the redox state, as well as an anoxia-induced depletion of α - and β -tocopherols.     

Changes in the fine-scale genetic structure of Finland through the 20th century

Information about individual-level genetic ancestry is central to population genetics, forensics and genomic medicine. So far, studies have typically considered genetic ancestry on a broad continental level, and there is much less understanding of how more detailed genetic ancestry profiles can be generated and how accurate and reliable they are. Here, we assess these questions by developing a framework for individual-level ancestry estimation within a single European country, Finland, and we apply the framework to track changes in the fine-scale genetic structure throughout the 20^th century. We estimate the genetic ancestry for 18,463 individuals from the National FINRISK Study with respect to up to 10 genetically and geographically motivated Finnish reference groups and illustrate the annual changes in the fine-scale genetic structure over the decades from 1920s to 1980s for 12 geographic regions of Finland. We detected major changes after a sudden, internal migration related to World War II from the region of ceded Karelia to the other parts of the country as well as the effect of urbanization starting from the 1950s. We also show that while the level of genetic heterogeneity in general increases towards the present day, its rate of change has considerable differences between the regions. To our knowledge, this is the first study that estimates annual changes in the fine-scale ancestry profiles within a relatively homogeneous European country and demonstrates how such information captures a detailed spatial and temporal history of a population. We provide an interactive website for the general public to examine our results.