Visualization of ribosomal DNA loci in spore interphasic nuclei of glomalean fungi by fluorescence in situ hybridization

 Fluorescence in situ hybridization (FISH) was applied to interphasic nuclei isolated from spores of four species of AM fungi : Scutellospora castanea, Glomus mosseae, Glomus intraradices and Gigaspora rosea. Ribosomal DNA loci were visualized using digoxigenin-labeled 25 S rDNA probes obtained by nested PCR. Several hybridization sites were detected per nucleus and an internuclear variability was observed in the number of loci. This is the first report of successful application of FISH to analyse the genomes of glomalean fungi. Accepted: 16 September 1998     

Structural investigation into the C‐terminal extension of the ene‐reductase from Ralstonia (Cupriavidus) metallidurans

Ene‐reductases (ERs), or Old Yellow Enzymes, catalyze the asymmetric reduction of various activated alkenes. This class of biocatalysts is considered an attractive alternative to current chemical technologies for hydrogenation due to their high selectivity and specificity. Here the X‐ray crystal structure of RmER, a “thermophilic”‐like ER from Ralstonia (Cupriavidus) metallidurans, is reported. Unlike other members of this class of ERs, RmER is monomeric in solution which we previously related to its atypical elongated C‐terminus. A typical dimer interface was however observed in our crystal structure, with the conserved Arg‐“finger” forming part of the adjacent monomer's active site and the elongated C‐terminus extending into the active site through contacting the “capping” domain. This dimerization also resulted in the loss of one FMN cofactor from each dimer pair. This potential transient dimerization and dissociation of FMN could conceivably explain the rapid rates previously observed when an FMN light‐driven cofactor regeneration system was used during catalysis with RmER.     

Urbanisation lowers great tit Parus major breeding success at multiple spatial scales

While numerous studies have reported negative effects of urbanisation on birds, few have examined the role of urban scale in influencing breeding success. Furthermore, many studies have relied on qualitative rather than quantitative assessments of urbanisation. This study sought to address these issues by testing the effects of urbanisation, measured at two spatial scales, on the breeding success of great tits Parus major. A nested study design, incorporating over 400 nestboxes, was used in study sites across northern Belgium with a priori quantified degrees of urbanisation at both local and regional scales. All measured breeding parameters were found to vary at one or both spatial scales of urbanisation; in more urbanised areas great tits displayed advanced laying dates but lower breeding success compared to rural areas, with smaller clutch sizes, lower nestling masses and fewer fledglings per egg. Importantly, urbanisation effects were not limited to big cities as birds breeding in gardens or parks in small towns also had comparatively low success. We found that both regional‐ and local‐scale urbanisation had consistent significant effects on laying date, clutch size and nestling mass, while the number of fledglings per egg was negatively influenced by local‐scale urbanisation only. Results of this study therefore highlight the importance of utilising multiple spatial scales in analysing urbanisation effects, as well as the potential negative impact of local urbanisation on breeding success. This calls for further investigation into mechanisms driving urbanisation effects and how these may vary at different scales.     

Agroecology: the key role of arbuscular mycorrhizas in ecosystem services

The beneficial effects of arbuscular mycorrhizal (AM) fungi on plant performance and soil health are essential for the sustainable management of agricultural ecosystems. Nevertheless, since the ‘first green revolution’, less attention has been given to beneficial soil microorganisms in general and to AM fungi in particular. Human society benefits from a multitude of resources and processes from natural and managed ecosystems, to which AM make a crucial contribution. These resources and processes, which are called ecosystem services, include products like food and processes like nutrient transfer. Many people have been under the illusion that these ecosystem services are free, invulnerable and infinitely available; taken for granted as public benefits, they lack a formal market and are traditionally absent from society’s balance sheet. In 1997, a team of researchers from the USA, Argentina and the Netherlands put an average price tag of US $33 trillion a year on these fundamental ecosystem services. The present review highlights the key role that the AM symbiosis can play as an ecosystem service provider to guarantee plant productivity and quality in emerging systems of sustainable agriculture. The appropriate management of ecosystem services rendered by AM will impact on natural resource conservation and utilisation with an obvious net gain for human society.     

Uptake and remodeling of exogenous phosphatidylethanolamine in E. coli

The fate of exogenous short-chain analogues of phosphatidylethanolamine and phosphatidylserine was studied in a deep-rough derivative of E. coli mutant strain AD93 that cannot synthesize phosphatidylethanolamine de novo. Using mass spectrometry, it was shown that dicaproyl(di 6:0)-phosphatidylethanolamine is extensively remodeled, eventually adopting the phosphatidylethanolamine species profile of the parental wild-type strain of AD93. Dicaproyl-phosphatidylserine was decarboxylated to form phosphatidylethanolamine, and yielded a species profile, which strongly resembled that of the introduced phosphatidylethanolamine. This demonstrates transport of phosphatidylserine to the cytosolic leaflet of the inner membrane. The changes of the species profile of phosphatidylethanolamine indicate that the short-chain phospholipids are most likely remodeled via two consecutive acyl chain substitutions, and at least part of this remodeling involves transport to the inner membrane.     

Widespread triazole pesticide use affects infection dynamics of a global amphibian pathogen

The sixth mass extinction is a consequence of complex interplay between multiple stressors with negative impact on biodiversity. We here examine the interaction between two globally widespread anthropogenic drivers of amphibian declines: the fungal disease chytridiomycosis and antifungal use in agriculture. Field monitoring of 26 amphibian ponds in an agricultural landscape shows widespread occurrence of triazole fungicides in the water column throughout the amphibian breeding season, together with a negative correlation between early season application of epoxiconazole and the prevalence of chytrid infections in aquatic newts. While triazole concentrations in the ponds remained below those that inhibit growth of Batrachochytrium dendrobatidis, they bioaccumulated in the newts' skin up to tenfold, resulting in cutaneous growth-suppressing concentrations. As such, a concentration of epoxiconazole, 10 times below that needed to inhibit fungal growth, prevented chytrid infection in anuran tadpoles. The widespread presence of triazoles may thus alter chytrid dynamics in agricultural landscapes.     

Erigeron astranthioides (Asteraceae: Astereae), a new epappose species from western Mexico

A new species,Erigeron astranthioides, apparently endemic to the Sierra Madre of central Durango, is described and illustrated. It is contrasted withE. forreri (Greene) Greene andAstranthium, both of which are similar, though apparently through convergence. The new species is part of a lineage that includes six other primarily epapposeErigeron species mostly from the western Sierra Madre; within this group its closest relative appears to beE. mimus (S. F. Blake) Nesom, with which it is compared.     

Excess portal venous long-chain fatty acids induce syndrome X via HPA axis and sympathetic activation

We tested the hypothesis that excessive portal venous supply of long-chain fatty acids to the liver contributes to the development of insulin resistance via activation of the hypothalamus-pituitary-adrenal axis (HPA axis) and sympathetic system. Rats received an intraportal infusion of the long-chain fatty acid oleate (150 nmol/min, 24 h), the medium-chain fatty acid caprylate, or the solvent. Corticosterone (Cort) and norepinephrine (NE) were measured as indexes for HPA axis and sympathetic activity, respectively. Insulin sensitivity was assessed by means of an intravenous glucose tolerance test (IVGTT). Oleate infusion induced increases in plasma Cort (Delta = 13.5 +/- 3.6 microg/dl; P < 0.05) and NE (Delta = 235 +/- 76 ng/l; P < 0.05), whereas caprylate and solvent had no effect. The area under the insulin response curve to the IVGTT was larger in the oleate-treated group than in the caprylate and solvent groups (area = 220 +/- 35 vs. 112 +/- 13 and 106 +/- 8, respectively, P < 0.05). The area under the glucose response curves was comparable [area = 121 +/- 13 (oleate) vs. 135 +/- 20 (caprylate) and 96 +/- 11 (solvent)]. The results are consistent with the concept that increased portal free fatty acid is involved in the induction of visceral obesity-related insulin resistance via activation of the HPA axis and sympathetic system.