Total fatty acid composition in the characterization and identification of orchid mycorrhizal fungi Epulorhiza spp.

Rhizoctonia-like fungi are the main mycorrhizal fungi in orchid roots. Morphological characterization and analysis of conserved sequences of genomic DNA are frequently employed in the identification and study of fungi diversity. However, phytopathogenic Rhizoctonia-like fungi have been reliably and accurately characterized and identified through the examination of the fatty acid composition. To evaluate the efficacy of fatty acid composition in characterizing and identifying Rhizoctonia-like mycorrhizal fungi in orchids, three Epulorhiza spp. mycorrhizal fungi from Epidendrum secundum, two unidentified fungi isolated from Epidendrum denticulatum, and a phytopathogenic fungus, Ceratorhiza sp. AGC, were grouped based on the profile of their fatty acids, which was assessed by the Euclidian and Mahalanobis distances and the UPGMA method. Dendrograms distinguished the phytopathogenical isolate of Ceratorhiza sp. AGC from the mycorrhizal fungi studied. The symbionts of E. secundum were grouped into two clades, one containing Epulorhiza sp.1 isolates and the other the Epulorhiza sp.2 isolate. The similarity between the symbionts of E. denticulatum and Epulorhiza spp. fungi suggests that symbionts found in E. denticulatum may be identified as Epulorhiza. These results were corroborated by the analysis of the rDNA ITS region. The dendrogram constructed based on the Mahalanobis distance differentiated the clades most clearly. Fatty acid composition analysis proved to be a useful tool for characterizing and identifying Rhizoctonia-like mycorrhizal fungi.

Convergent genetic architecture underlies social organization in ants.

Complex adaptive polymorphisms are common in nature, but what mechanisms maintain the underlying favorable allelic combinations [1-4]? The convergent evolution of polymorphic social organization in two independent ant species provides a great opportunity to investigate how genomes evolved under parallel selection. Here, we demonstrate that a large, nonrecombining "social chromosome" is associated with social organization in the Alpine silver ant, Formica selysi. This social chromosome shares architectural characteristics with that of the fire ant Solenopsis invicta [2], but the two show no detectable similarity in gene content. The discovery of convergence at two levels-the phenotype and the genetic architecture associated with alternative social forms-points at general genetic mechanisms underlying transitions in social organization. More broadly, our findings are consistent with recent theoretical studies suggesting that suppression of recombination plays a key role in facilitating coordinated shifts in coadapted traits [5, 6].

Chemical and structural characterization of soil humic substances under agroforestry and conventional systems

Studies have proven that the agroforestry systems in the semi-arid region of the State of Ceará, Brazil, induce an increase in soil organic C levels. Notwithstanding, there is no information if this increase also results in qualitative changes in different pools of soil organic matter. The objective of this study was to verify the possible chemical and structural alterations in fulvic and humic acids of a Luvisol in areas adopting agroforestry, traditional intensive cultivation and native forest in a long-term experiment conducted in the semi-arid region of Ceará State, Brazil. The study was conducted in an experimental area of the National Goat Research Center (Embrapa) in Sobral, CE. The following treatments were evaluated: agrosilvopasture (AGP), silvopasture (SILV), intensive cultivation under fallow (ICF), and areas with native forest (NF). Soil fulvic and humic acids fractions were extracted from the 0-6 and 6-12 cm layers and characterized by elemental composition, thermogravimetry and infrared spectroscopy analyses. The elemental composition analysis of humic acids confirmed the data found for fulvic acids, showing reduction in the C, H and N levels, followed by an increase in O contents in the AGP and ICF treatments over SILV and NF. In all treatments, except to SILV in the 0-6 cm layer, the percentage of mass loss was highest (300-600 °C) for humic acids in the thermally most stable region. Despite the similarity between infrared spectra, soil fulvic acids in the SILV treatment extracted from 6-12 cm depth decrease the absorption bands at 1708 and 1408 cm-1 followed by an increase in the absorption band at 1608 cm-1 attributed to aromatic C=C groups. This behavior suggests an increase in the aromatic character of the structure. The AGP and ICF treatments, which increase the soil tilling, favored the maintenance of humic substances with a more aromatic character in the soil than SILV and NF. The less aromatic humic substances in the SILV treatment resulted in an increase of exchange sites of soil organic matter, indicating improved nutrient cycling and maintenance of productivity in the system.

Promoter recognition and activation by the global response regulator CbrB in Pseudomonas aeruginosa.

In Pseudomonas aeruginosa, the CbrA/CbrB two-component system is instrumental in the maintenance of the carbon-nitrogen balance and for growth on carbon sources that are energetically less favorable than the preferred dicarboxylate substrates. The CbrA/CbrB system drives the expression of the small RNA CrcZ, which antagonizes the repressing effects of the catabolite repression control protein Crc, an RNA-binding protein. Dicarboxylates appear to cause carbon catabolite repression by inhibiting the activity of the CbrA/CbrB system, resulting in reduced crcZ expression. Here we have identified a conserved palindromic nucleotide sequence that is present in upstream activating sequences (UASs) of promoters under positive control by CbrB and σ(54) RNA polymerase, especially in the UAS of the crcZ promoter. Evidence for recognition of this palindromic sequence by CbrB was obtained in vivo from mutational analysis of the crcZ promoter and in vitro from electrophoretic mobility shift assays using crcZ promoter fragments and purified CbrB protein truncated at the N terminus. Integration host factor (IHF) was required for crcZ expression. CbrB also activated the lipA (lipase) promoter, albeit less effectively, apparently by interacting with a similar but less conserved palindromic sequence in the UAS of lipA. As expected, succinate caused CbrB-dependent catabolite repression of the lipA promoter. Based on these results and previously published data, a consensus CbrB recognition sequence is proposed. This sequence has similarity to the consensus NtrC recognition sequence, which is relevant for nitrogen control.

Alzheimer disease: curly fibers and tangles in organs other than brain.

The filamentous brain lesions that define Alzheimer disease (AD) consist of senile plaques and neurofibrillary tangles. Undulated pathological filaments--curly fibers or neuropil threads--also occur in the neuropil. Beta-amyloid precursor proteins are synthesized by many cells outside the central nervous system and recently, deposition of beta-amyloid-protein was reported to occur in non-neuronal tissues. In addition, increasing data claim the importance of chronic inflammation in the pathogenesis of AD. These observations suggest that AD may be a widespread systemic disorder. Here we report that pathological argyrophilic filaments with histochemical properties of amyloid showing striking morphological similarity to curly fibers and/or tangles accumulate not only in ependymal layer and in epithelial cells of choroid plexus, but also in several other organs (e.g. liver, pancreas, ovary, testis, thyroid) in AD. The ependyma, choroid plexus, and various organs of 39 autopsy cases were analyzed. In search of curly fiber and tangle-like changes in organs other than brain, 395 blocks from 21 different tissues of 24 AD cases, 5 cases with discrete or moderate AD-type changes, and 10 control cases were investigated. We found in non-neuronal cells "curly fibers" or "tangles" immunoreactive with antibodies to P component, Tau-protein, ubiquitin, fibronectin, and Apolipoprotein-E, but lacking immunoreactivity with antibodies to neurofilament proteins. Ultrastructurally they consist of densely packed straight and paired helical filaments and closely resemble neurofibrillary tangles and neuropil threads. These observations indicate that the formation of "curly fibers" and "tangles" is not unique to the central nervous system. The results suggest that AD might be a systemic disorder or that similar fibrillary changes to tangles and curly fibers may also be associated with other amyloidosis than beta-amyloidosis. Further investigations are necessary to understand the pathogenetic interest of these fibrillary changes outside the CNS.