Characterisation of the laccase-encoding gene abr2 of the dihydroxynaphthalene-like melanin gene cluster of Aspergillus fumigatus

Aspergillus fumigatus is an important pathogen of the immunocompromised host. Previously, it was shown that the polyketide synthase encoded by the pksP (alb1) gene represents a virulence determinant. pksP is part of a gene cluster involved in dihydroxynaphthalene (DHN)-like melanin biosynthesis. Because a putative laccase-encoding gene (abr2) is also part of the cluster and a laccase was found to represent a virulence factor in Cryptococcus neoformans, here, the Abr2 laccase was characterised. Deletion of the abr2 gene changed the gray-green conidial pigment to a brown color and the ornamentation of conidia was reduced compared with wild-type conidia. In contrast to the white pksP mutant, the susceptibility of the Δabr2 mutant against reactive oxygen species (ROS) was not increased, suggesting that the intermediate of DHN-like melanin produced up to the step catalysed by Abr2 already possesses ROS scavenging activity. In an intranasal mouse infection model, the Δabr2 mutant strain showed no reduction in virulence compared with the wild type. In the Δabr2 mutant, overall laccase activity was reduced only during sporulation, but not during vegetative growth. An abr2p-lacZ gene fusion was expressed during sporulation, but not during vegetative growth confirming the pattern of laccase activity due to Abr2.     

Über rein glabellare karapaxbildungen bei milben und über die umgestaltung des vorderkörpers der ixodidea als folge der gnathosomaentstehung

Zusamrnenfassung Es wird gezeigt, daß sich die ursprüngliche Längsdreiteilung der Segmente des Arachnoidenkörpers bei manchen Milben auch darin äußert, daß der Rückenschild nicht wie gewöhnlich bei den Spinnentieren aus den verschmolzenen Meso- und Pleurotergiten besteht, sondern sich allein aus der Mittelspindel (Glabella) aufbaut.Es werden am Beispiel der Ixodiden die morphologischen Verände-rungen beschrieben, die infolge der Abgliederung des vorderen Körper-endes als Gnathosoma bei den Milben auftreten. Das dorsale eingesenkte Zwischenstück zwischen Gnathosoma und restlichem Karapax ist ebenfalls rein glabellarer Herkunft.Die merkwürdige Eiablagevorrichtung der Zeeken, das Génésche Organ, wird in seinem Ban beschrieben und versucht, es auf die Chelicerendrüsen anderer Arachnomorphen zurückzuführen.     

Repertoire diversity of antibody response to bacterial antigens in aged mice. II. Phosphorylcholine-antibody in young and aged mice differ in both VH/VL gene repertoire and in specificity

Aging of mice is accompanied by both quantitative and qualitative changes in antibody responses to phosphorylcholine (PC), an immunodominant epitope of Streptococcus pneumoniae R36a strain (Pn). In order to study these changes at the molecular level, we generated PC-specific hybridomas from young (3 to 4 mo) and aged (20 to 24 mo) mice of different strains after primary immunization with S. pneumoniae R36a strain. These mAb were tested for Ig VH and VL gene family utilization, idiotopic repertoire, and cross-reactivity with unrelated Ag. Hybridomas from young mice (BALB/c, C57BL/6, and D1.LP) uniformly expressed the VH-S107 and V kappa-22 genes as well as most idiotopes of the T15 family, which were identified with different anti-T15 mAb. In contrast, the PC-reactive mAb from aged mice were quite heterogeneous: only 2 out of 13 utilized VHS107, 1 of 13 used VH7183, and 3 of 13 used VHJ558 gene family. Moreover, none of these mAb used L chain encoded by V kappa 22(0/13), but surprisingly they frequently expressed some of the T15 idiotope. In addition, the PC-binding mAb from aged mice showed broad cross-reactivity with various mouse and foreign proteins, whereas the mAb from young mice did not. These results demonstrate the genetic shift in antibody response of aging mice to PC, which is accompanied by a change in the antibody specificity. Interestingly, the qualitative repertoire change appears to be unrelated to the magnitude of antibody response, for the aged BALB/c mice maintain a very high reactivity to PC.     

The brain is getting ready for dinner

Every evening, as we get ready for dinner, in addition to the routine behaviors of preparing the meal itself, we also prepare our bodies to cope with the upcoming meal. This could take the form of making restaurant reservations, changing into appropriate attire, washing hands, priming ourselves with an aperitif, or even consciously avoiding snacks as the meal approaches. A study by Johnstone and colleagues in this issue of Cell Metabolism (Johnstone et al., 2006) provides evidence that in parallel to our learned preparatory behaviors, our central nervous system is going through comparable motions as it gets ready for the anticipated meal.     

Acclimation response of spring wheat in a free-air CO2 enrichment (FACE) atmosphere with variable soil nitrogen regimes. 1. Leaf position and phenology determine acclimation response

We have examined the photosynthetic acclimation of wheat leaves grown at an elevated CO₂ concentration, and ample and limiting N supplies, within a field experiment using free-air CO₂ enrichment (FACE). To understand how leaf age and developmental stage affected any acclimation response, measurements were made on a vertical profile of leaves every week from tillering until maturity. The response of assimilation (A) to internal CO₂ concentration (C_i) was used to estimate the in vivo carboxylation capacity (Vc_max) and maximum rate of ribulose-1,5-bisphosphate limited photosynthesis (A _sat). The total activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), and leaf content of Rubisco and the Light Harvesting Chlorophyll a/b protein associated with Photosystem II (LHC II), were determined. Elevated CO₂ did not alter Vc_max in the flag leaf at either low or high N. In the older shaded leaves lower in the canopy, acclimatory decline in Vc_max and A _sat was observed, and was found to correlate with reduced Rubisco activity and content. The dependency of acclimation on N supply was different at each developmental stage. With adequate N supply, acclimation to elevated CO₂ was also accompanied by an increased LHC II/Rubisco ratio. At low N supply, contents of Rubisco and LHC II were reduced in all leaves, although an increased LHC II/Rubisco ratio under elevated CO₂ was still observed. These results underscore the importance of leaf position, leaf age and crop developmental stage in understanding the acclimation of photosynthesis to elevated CO₂ and nutrient stress. This revised version was published online in June 2006 with corrections to the Cover Date.     

The RootChip: an integrated microfluidic chip for plant science

Studying development and physiology of growing roots is challenging due to limitations regarding cellular and subcellular analysis under controlled environmental conditions. We describe a microfluidic chip platform, called RootChip, that integrates live-cell imaging of growth and metabolism of Arabidopsis thaliana roots with rapid modulation of environmental conditions. The RootChip has separate chambers for individual regulation of the microenvironment of multiple roots from multiple seedlings in parallel. We demonstrate the utility of The RootChip by monitoring time-resolved growth and cytosolic sugar levels at subcellular resolution in plants by a genetically encoded fluorescence sensor for glucose and galactose. The RootChip can be modified for use with roots from other plant species by adapting the chamber geometry and facilitates the systematic analysis of root growth and metabolism from multiple seedlings, paving the way for large-scale phenotyping of root metabolism and signaling.     

Participatory rural appraisal of ecosystem services of wetlands in the Amazonian Piedmont of Colombia: elements for a sustainable management concept

Considering the rapid changes in land use in tropical countries and the difficulties of law enforcement in remote areas, management of ecosystems benefits from the landscape approach. Within the landscape approach it is important to assess the different livelihoods of the local populations, as well as the vulnerability of the ecosystems that are supporting these livelihoods. Specifically for wetlands in rural tropical areas that face fast developing agro-industrial land use change, there is little information available on the attitude of stakeholders considering the ecosystems they manage. We used a combination of participatory rural appraisal and participatory mapping methods on rural wetlands in the Amazonian Piedmont region in Colombia, an area that has hardly ever been studied. We found that 77.7 % of the current livelihoods depend directly on the provisioning ecosystem services delivered by the wetlands, where fishing and hunting are the most important services that contribute to the household income. Ecotourism, which is emerging as a promising source of income, was also pointed as one key ecosystem service. However, our results revealed that the wetlands in our study area are very vulnerable (up to 41 % endangered). The main causes for wetland deterioration were cattle ranching, invasive grasses, deforestation, drainage, and burning. We conclude with a brief overview on the pros and cons of reconciling wetland conservation and human development in sensitive regions such as the Amazonian Piedmont in Colombia and other similar regions in the Tropics.