Transgenic Medicago truncatula plants that accumulate proline display nitrogen-fixing activity with enhanced tolerance to osmotic stress

Legume root nodule nitrogen-fixing activity is severely affected by osmotic stress. Proline accumulation has been shown to induce tolerance to salt stress, and transgenic plants over-expressing Delta(1)-pyrroline-5-carboxylate synthetase (P5CS), which accumulates high levels of proline, display enhanced osmotolerance. Here, we transformed the model legume Medicago truncatula with the P5CS gene from Vigna aconitifolia, and nodule activity was evaluated under osmotic stress in transgenic plants that showed high proline accumulation levels. Nitrogen fixation was significantly less affected by salt treatment compared to wild-type (WT) plants. To our knowledge, this is the first time that transgenic legumes have been produced that display nitrogen-fixing activity with enhanced tolerance to osmotic stress. We studied the expression of M. truncatula proline-related endogenous genes M. truncatulaDelta(1)-pyrroline-5-carboxylate synthetase 1 (MtP5CS1), M. truncatulaDelta(1)-pyrroline-5-carboxylate synthetase 2 (MtP5CS2), M. truncatula ornithine delta-aminotransferase (MtOAT), M. truncatula proline dehydrogenase (MtProDH) and a proline transporter gene in both WT and transgenic plants. Our results indicate that proline metabolism is finely regulated in response to osmotic stress in an organ-specific manner. The transgenic model allowed us to analyse some of the biochemical and molecular mechanisms that are activated in the nodule in response to high salt conditions, and to ascertain the essential role of proline in the maintenance of nitrogen-fixing activity under osmotic stress.     

Enzymes in Bast Fibrous Plant Processing

The program COST Action 847 Textile Quality and Biotechnology (2000–2005) has given an excellent chance to review the possibilities of the research, aiming at development of the industrial application of enzymes for bast fibrous plant degumming and primary processing. The recent advancements in enzymatic processing of bast fibrous plants (flax, hemp, jute, ramie and alike plants) and related textiles are given. The performance of enzymes in degumming, modification of bast fibres, roving, yarn, related fabrics as well as enzymatic bonding of lignocellulosic composites is provided.     

Seasonal variability in the palatability of freshwater macrophytes: a case study

The pond snail Lymnaea stagnalis (L.) was used for a laboratory assessment of seasonal variation in palatability of three freshwater macrophytes: Potamogeton lucens, Elodea canadensis and E. nuttallii. For each species, 2–5 populations were investigated in spring and in summer. Preliminary results showed that the feeding rate of similarly-aged snails bred under standard conditions was stable over time. In contrast, snail feeding rate on the three macrophyte species decreased from spring to summer, which was therefore interpreted as a decrease in plant palatability. This decrease was probably due to tissue maturation, as suggested by the concomitant increase in the dry matter content of leaves of the three species. The high palatability of the species studied during the spring may prove detrimental in cases of strong herbivore pressure, and could have consequences for macrophyte distribution among aquatic habitats.     

Für welche Pflanzenarten hat die Schweiz eine internationale Verantwortung?

Eggenberg S. and Landolt E. 2006. For which plant species does Switzerland have an international responsibility? Bot. Helv. 116: 119 – 133. Priorities in plant species conservation are often based on national Red Lists. In an international context, however, the Red List status (threat) of a species within a limited territory may be misleading because the local disappearance of a species may or may not have serious implications for its global persistence. A second important aspect to consider in species conservation is therefore the responsibility of a country for the species, i.e. the importance of the conservation of local populations for the persistence of the species worldwide. In this contribution, we assess the responsibility of Switzerland for its vascular flora using three biogeographical criteria: (1) the Swiss portion of the species range (high responsibility for species with a large fraction of the range in Switzerland), (2) the degree of endemism (high responsibility for species with a small total range) and (3) the degree of isolation (high responsibility for isolated outposts, which may contain a large part of a species’ genetic variation). The three criteria were derived for each species from global and European distribution maps, and were then combined to an overall index of responsibility. On this basis, 397 taxa for which Switzerland has an intermediate to high international responsibility were identified. These are almost 15% of the whole vascular flora of Switzerland. Of the 397 taxa, 75% are endemic species of the Alps, and 48% are threatened taxa within Switzerland. The Responsibility List can be used together with the Red List to set priorities in plant conservation or to identify areas of particular floristic value. Manuskript angenommen am 11. September 2006     

Characterization of an unusual folding pattern in a catalytically active guanine quadruplex structure

In the presence of certain metal ions, DNA and RNA can form guanine quadruplex structures, which have been proposed to play a functional role in a variety of biological processes. An 18-nucleotide DNA oligomer, PS2.M, d(GTG3TAG3CG3T2G2), was previously reported to bind hemin and the resulting complex exhibited peroxidase activity. It was proposed that PS2.M folds unimolecularly into an antiparallel quadruplex with unusual, single-base loops and terminal guanines positioned in adjacent quartets. Here we describe structural and stability properties of PS2.M alone in different buffers and metal ions, using gel electrophoresis, circular dichroism (CD), ultraviolet (UV)-visible spectroscopies, and one-dimensional 1H nuclear magnetic resonance (NMR). Native gel behavior of PS2.M in the presence of either Na+ or Pb2+ suggests the formation of unimolecular structures but, in the presence of K+, both unimolecular and multistranded structures are observed. In the presence of Pb2+ ions, PS2.M forms a unimolecular quadruplex containing three guanine quartets. CD titrations reveal that binding of Pb2+ ions to PS2.M is stoichiometric, and a single lead cation suffices to fully fold PS2.M. The PS2.M-Na+ system also forms a similar unimolecular quadruplex. In the presence of K+, the PS2.M-K+ system forms mixed species. With increasing time and PS2.M concentration, the contribution of unimolecular species decreases while that of multimolecular species increases, and this behavior is independent of buffer media. These results suggest that the catalytically active form, studied in the presence of K+, may be a parallel, multistranded quadruplex rather than an antiparallel, unimolecular quadruplex.     

The orientation effect of gramicidin A on bicelles and Eu3+ -doped bicelles as studied by solid-state NMR and FT-IR spectroscopy

We have explored the effect of gramicidin A (gA) on bicelle (Bic) orientation in the absence and presence of Eu(3+) by (31)P and (2)H NMR at different DMPC/gA ratios. FT-IR spectroscopy was used to assess the lipid chain ordering and verify the transmembrane peptide conformation. Our results show a time-dependent flipping of the bilayer normal alignment at high temperatures and high proportion of gA. The results are explained by both the diamagnetic susceptibility anisotropy of the beta(6.3) helical peptides and viscosity of the lipid mixture. The concentration effect of gramicidin on Bic/Eu(3+) is compared to that on Eu(3+)-doped DMPC liposomes. The Bic/Eu(3+) system is no longer oriented in the presence of gA and adopts a vesicular morphology while the peptide incorporation induces the formation of ellipsoidal DMPC/Eu(3+) assemblies aligned with their normal parallel to the magnetic field. The difference is explained in terms of lipid chain disorder and size of the bilayers.     

Death of stoma guard cells in leaf epidermis under disturbance of energy provision

Cyanide is an apoptosis inducer in stoma guard cells from pea leaf epidermis. Unlike CN-, the uncoupler of oxidative and photosynthetic phosphorylation carbonyl cyanide m-chlorophenylhydrazone (CCCP), the combination of CCCP, 3-(3 ,4 -dichlorophenyl)-1,1-dimethylurea (DCMU), benzylhydroxamate (BH), myxothiazol, antimycin A, and a glycolysis inhibitor 2-deoxyglucose (DG) did not induce destruction of guard cell nuclei for 20 h of incubation of epidermal peels in the light. DCMU prevented the effect of CN- as a programmed cell death (PCD) inducer. CCCP, the combination of DCMU and CCCP, or the combination of DCMU, CCCP, BH, myxothiazol, antimycin A, and DG supplemented by CN- caused destruction of cell nuclei; the number of the cells lacking nuclei in this case was higher than with CN- alone. DG and CCCP caused cell destruction after longer incubation of the isolated epidermis - after 2 days and to a greater degree after 4 days. The effect of DG and CCCP was reduced by illumination. Cell destruction during long-term incubation was prevented by the combination of DG and CCCP. From data of electron microscopy, DCMU and dinitrophenyl ester of iodonitrothymol (DNP-INT) prevented apoptotic changes of the nuclear ultrastructure induced by CN-. The suppression of the destruction of the guard cell nuclei under combined action of DG and CCCP was apparently caused by switching of cell death from PCD to necrosis. Thus, the type of cell death - via apoptosis or necrosis - is controlled by the level of energy provision.