Soil carbonate drives local adaptation in Arabidopsis thaliana

High soil carbonate limits crop performance especially in semiarid or arid climates. To understand how plants adapt to such soils, we explored natural variation in tolerance to soil carbonate in small local populations (demes) of Arabidopsis thaliana growing on soils differing in carbonate content. Reciprocal field‐based transplants on soils with elevated carbonate (+C) and without carbonate (?C) over several years revealed that demes native to (+C) soils showed higher fitness than those native to (?C) soils when both were grown together on carbonate‐rich soil. This supports the role of soil carbonate as a driving factor for local adaptation. Analyses of contrasting demes revealed key mechanisms associated with these fitness differences. Under controlled conditions, plants from the tolerant deme A1_(+C) native to (+C) soil were more resistant to both elevated carbonate and iron deficiency than plants from the sensitive T6_(?C) deme native to (?C) soil. Resistance of A1_(+C) to elevated carbonate was associated with higher root extrusion of both protons and coumarin‐type phenolics. Tolerant A1_(+C) also had better Ca‐exclusion than sensitive T6_(?C). We conclude that Arabidopsis demes are locally adapted in their native habitat to soils with moderately elevated carbonate. This adaptation is associated with both enhanced iron acquisition and calcium exclusion.     

New challenges in the management of the Brazilian Pantanal and catchment area

The Pantanal wetland is a vast seasonally inundated area of extraordinary landscape and biological diversity and complexity. It is located in the upper portion of the Paraguay River basin in central South America. During the rainy season, increased stream discharge from the surrounding basin produces an annual flood pulse through the Pantanal. Increasing human impact, such as dam construction, deforestation, agricultural related activities, and the Hidrovia project in the Parana-Paraguay waterway, threaten the ecological stability of the Pantanal area. As a result, there is an urgent need to introduce new management practices in the Pantanal Basin. In this paper we present a concept for managing the Pantanal catchment based on the integration of ecological knowledge, institutional organization, and involvement of different stakeholders. We propose approaches for an integrated management of the Pantanal and its catchment based on improving data bases and the empowerment of the stakeholder groups. The latter depends on increasing the level of education and access to information, as well as implementing procedures to improve public involvement and enforcement of environmental regulations.This revised version was published online in March 2005 with corrections to the issue cover date.     

Protein extraction and comparison of stain protocols for analysis of two-dimensional electrophoresis gels

Protein extraction and the proteome of Lactobacillus delbrueckii subsp. bulgaricus were studied using different stains. The reversible silver staining technique was shown to be more sensitive than the irreversible silver stain. Coomassie colloidal was demonstrated to be as sensitive as reversible silver stain; however, the Coomassie colloidal blue solution developed a higher background and for sample preparation was more time-consuming.     

Mitochondrial apoptotic cell death and moderate superoxide generation upon selective activation of non-desensitizing AMPA receptors in hippocampal cultures

In the present work we investigated the effect of selective stimulation of non-desensitizing alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptors in the intracellular processes leading to hippocampal neuronal death and production of reactive oxygen species (ROS). Activation of AMPA receptors in the presence of cyclothiazide (CYZ), a blocker of AMPA receptor desensitization, resulted in the death of approximately 25% of neurones, which was prevented by 2,3-dihydroxy-6-nitro-7-sulphamoyl-benzo(f)quinoxaline (NBQX), an AMPA-preferring receptor antagonist. (+)-5-Methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine hydrogen maleate (MK-801) protected the neurones from necrotic death induced by AMPA or NMDA receptor activation. Neurodegeneration caused by selective activation of non-desensitizing AMPA receptors, in the presence of AMPA, CYZ and MK-801, significantly decreased the number of Co2+-positive neurones, used as a cytochemical marker of Ca2+-permeable AMPA receptors, but maintained intracellular ATP/ADP. The AMPA-mediated apoptotic cell death involved mitochondrial cytochrome c release and the activation of caspases-1 and -3, which was prevented by NBQX. Interestingly, although selective activation of AMPA receptors was not associated with production of intracellular peroxides, a moderate increase in superoxide production was observed upon exposure to antimycin A (AA). Furthermore, increased activity of Mn- superoxide dismutase (SOD) was observed on selective activation of non-desensitizing AMPA receptors. Taken together, these data make important contributions to the elucidation of the downstream pathways activated in AMPA receptor-mediated excitotoxicity in cultured rat hippocampal neurones.     

Expression of a fungal hydrophobin in the Saccharomyces cerevisiae cell wall: effect on cell surface properties and immobilization

The aim of this work was to modify the cell surface properties of Saccharomyces cerevisiae by expression of the HFBI hydrophobin of the filamentous fungus Trichoderma reesei on the yeast cell surface. The second aim was to study the immobilization capacity of the modified cells. Fusion to the Flo1p flocculin was used to target the HFBI moiety to the cell wall. Determination of cell surface characteristics with contact angle and zeta potential measurements indicated that HFBI-producing cells are more apolar and slightly less negatively charged than the parent cells. Adsorption of the yeast cells to different commercial supports was studied. A twofold increase in the binding affinity of the hydrophobin-producing yeast to hydrophobic silicone-based materials was observed, while no improvement in the interaction with hydrophilic carriers could be seen compared to that of the parent cells. Hydrophobic interactions between the yeast cells and the support are suggested to play a major role in attachment. Also, a slight increase in the initial adsorption rate of the hydrophobin yeast was observed. Furthermore, due to the engineered cell surface, hydrophobin-producing yeast cells were efficiently separated in an aqueous two-phase system by using a nonionic polyoxyethylene detergent, C(12-18)EO(5).     

P14ARF promotes accumulation of SUMO-1 conjugated (H)Mdm2

p14ARF tumour suppressor stabilises and activates p53 by directly interacting with (H)Mdm2 [(human) murine double minute 2 homologue] and inhibiting its E3 ubiquitin ligase activity. Here we demonstrate that p14ARF promotes accumulation of (H)Mdm2 conjugated to the small ubiquitin-like protein SUMO-1. Mutational analysis demonstrated that the N-terminus of Mdm2 is a target for p14ARF-mediated SUMO conjugation. SUMO modification requires residues 2-14 in p14ARF that interact with (H)Mdm2 and residues 82-101 in exon 2 involved in nucleolar localisation of p14ARF. These data suggest a novel role for p14ARF as a regulator of activity of (H)Mdm2, which could be related to its tumour suppressing activities.     

Integration of the cytogenetic and genetic linkage maps of Brassica oleracea

We have assigned all nine linkage groups of a Brassica oleracea genetic map to each of the nine chromosomes of the karyotype derived from mitotic metaphase spreads of the B. oleracea var. alboglabra line A12DHd using FISH. The majority of probes were BACs, with A12DHd DNA inserts, which give clear, reliable FISH signals. We have added nine markers to the existing integrated linkage map, distributed over six linkage groups. BACs were definitively assigned to linkage map positions through development of locus-specific PCR assays. Integration of the cytogenetic and genetic linkage maps was achieved with 22 probes representing 19 loci. Four chromosomes (2, 4, 7, and 9) are in the same orientation as their respective linkage groups (O4, O7, O8, and O6) whereas four chromosomes (1, 3, 5, and 8) and linkage groups (O3, O9, O2, and O1) are in the opposite orientation. The remaining chromosome (6) is probably in the opposite orientation. The cytogenetic map is an important resource for locating probes with unknown genetic map positions and is also being used to analyze the relationships between genetic and cytogenetic maps.