Morphology of the prothoracic discs and associated sensilla of Acanthocnemus nigricans (Coleoptera, Acanthocnemidae)

The Australian ‘little ash beetle’ Acanthocnemus nigricans (Coleoptera, Cleroidea, Acanthocnemidae) is attracted by forest fires. A. nigricans has one pair of unique prothoracic sensory organs and it has been speculated that these organs may play a role in fire detection. Each organ consists of a cuticular disc, which is fixed over an air-filled cavity. On the outer surface of the disc, about 90 tiny cuticular sensilla are situated. The poreless outer peg of a sensillum is 3–5 μm long and is surrounded by a cuticular wall. One ciliary sensory cell innervates the peg. As a special feature, the outer dendritic segment is very short already terminating below the cuticle. A massive electron-dense cylindrical rod, which most probably represents the hypertrophied dendritic sheath, extends through the cuticular canal connecting the tip of the outer dendritic segment to the peg. The dendritic inner segment and the soma are fused indistinguishably. Thin, leaflike extensions of glial cells deeply extend into that conjoint and considerably enlarged compartment which also contains large numbers of mitochondria. In summary, the sensilla of the sensory disc of A. nigricans represent a new type of insect sensillum of hitherto unknown function. The possible role of the prothoracic sensory organ in fire detection is discussed.     

The Golgi-Localized γ-Ear-Containing ARF-Binding (GGA) Proteins Alter Amyloid-β Precursor Protein (APP) Processing through Interaction of Their GAE Domain with the Beta-Site APP Cleaving Enzyme 1 (BACE1)

Proteolytic processing of amyloid-β precursor protein (APP) by beta-site APP cleaving enzyme 1 (BACE1) is the initial step in the production of amyloid beta (Aβ), which accumulates in senile plaques in Alzheimer’s disease (AD). Essential for this cleavage is the transport and sorting of both proteins through endosomal/Golgi compartments. Golgi-localized γ-ear-containing ARF-binding (GGA) proteins have striking cargo-sorting functions in these pathways. Recently, GGA1 and GGA3 were shown to interact with BACE1, to be expressed in neurons, and to be decreased in AD brain, whereas little is known about GGA2. Since GGA1 impacts Aβ generation by confining APP to the Golgi and perinuclear compartments, we tested whether all GGAs modulate BACE1 and APP transport and processing. We observed decreased levels of secreted APP alpha (sAPPα), sAPPβ, and Aβ upon GGA overexpression, which could be reverted by knockdown. GGA-BACE1 co-immunoprecipitation was impaired upon GGA-GAE but not VHS domain deletion. Autoinhibition of the GGA1-VHS domain was irrelevant for BACE1 interaction. Our data suggest that all three GGAs affect APP processing via the GGA-GAE domain.     

Cathepsins B, K, and L are regulated by a defined collagen type II peptide via activation of classical protein kinase C and p38 MAP kinase in articular chondrocytes

Degradation of the extracellular matrix (ECM) is a prominent feature in osteoarthritis (OA), which is mainly because of the imbalance between anabolic and catabolic processes in chondrocytes resulting in cartilage and bone destruction. Various proteases act in concert to degrade matrix components, e.g. type II collagen, MMPs, ADAMTS, and cathepsins. Protease-generated collagen fragments may foster the destructive process. However, the signaling pathways associated with the action of collagen fragments on chondrocytes have not been clearly defined. The present data demonstrate that the N-terminal telopeptide of collagen type II enhances expression of cathepsins B, K, and L in articular chondrocytes at mRNA, protein, and activity levels, mediated at least in part through extracellular calcium. We also demonstrate that the induction is associated with the activation of protein kinase C and p38 MAP kinase.     

Drought Effects in Climate Change Manipulation Experiments: Quantifying the Influence of Ambient Weather Conditions and Rain-out Shelter Artifacts

Extreme drought events challenge ecosystem functioning. Ecological response to drought is studied worldwide in a growing number of field experiments by rain-out shelters. Yet, few meta-analyses face severe challenges in the comparability of studies. This is partly because build-up of drought stress in rain-out shelters is modified by ambient weather conditions. Rain-out shelters can further create confounding effects (radiation, temperature), which may influence plant responses. Yet, a quantification of ecophysiological effects within rain-out shelters under opposing ambient weather conditions and of microclimatological artifacts is missing. Here, we examined phytometers—standardized potted individuals of Plantago lanceolata—under rain-out shelter, rain-out shelter artifact control, and ambient control during opposing outside microclimatological conditions. Furthermore, we tested for artifacts of rain-out shelters on plant responses in a long-term semi-natural grassland experiment. Phytometer plants below the rain-out shelters showed lower stomatal conductance, maximum quantum efficiency, and leaf water potential during warm ambient conditions with high evaporative demand than during cold conditions with low evaporative demand. Plant performance was highly correlated with ambient temperature and vapor pressure deficit (VPD). Rain-out shelter artifacts on plant responses were nonsignificant. Rain-out shelters remain a viable tool for studying ecosystem responses to drought. However, drought manipulations using rain-out shelters are strongly modified by ambient weather conditions. Attributing the results from rain-out shelter studies to drought effects and comparability among studies and study years therefore requires the quantification of the realized drought stress, for example, by relating ecosystem responses to measured microclimatological parameters such as air temperature and VPD.     

The dual-targeted RNA editing factor AEF1 is universally conserved among angiosperms and reveals only minor adaptations upon loss of its chloroplast or its mitochondrial target

Plant Molecular Biology - Upon loss of either its chloroplast or mitochondrial target, a uniquely dual-targeted factor for C-to-U RNA editing in angiosperms reveals low evidence for improved...