Amplification activation loop between caspase-8 and -9 dominates artemisinin-induced apoptosis of ASTC-a-1 cells

Although caspases have been demonstrated to be involved in artemisinin (ARTE)-induced apoptosis, their exact functions are not well understood. The aim of this report is to explore the roles of caspase-8, -9 and -3 during ARTE-induced apoptosis in human lung adenocarcinoma (ASTC-a-1) cells. ARTE treatment induces a rapid generation of reactive oxygen species (ROS), and ROS-dependent apoptosis as well as the activation of caspase-8, -9 and -3 via time- and dose-dependent fashion. Of upmost importance, inhibition of caspase-8 or -9, but not caspase-3, almost completely blocks the ARTE-induced not only activation of the caspase-8, -9 and -3 but also apoptosis. In addition, the apoptotic process triggered by ARTE does not involve the Bid cleavage, tBid translocation, significant loss of mitochondrial membrane potential and cytochrome c release from mitochondria. Moreover, silencing Bax/Bak does not prevent the ATRE-induced cell death as well as the activation of caspase-8, -9 and -3. Collectively, our data firstly demonstrate that ARTE triggers a ROS-mediated positive feedback amplification activation loop between caspase-8 and -9 independent of mitochondria, which dominantly mediated the ARTE-induced apoptosis via a caspase-3-independent apoptotic pathway in ASTC-a-1 cells. Our findings imply a potential to develop new derivatives from artemisinin to effectively initiate the amplification activation loop of caspases.     

Cold tolerance of the coconut hispine beetle, <Emphasis Type="Italic">Brontispa longissima</Emphasis> (Coleoptera: Chrysomelidae) in Japan

The coconut hispine beetle, Brontispa longissima (Gestro), supposedly originated from Papua New Guinea and Indonesia but has recently invaded Southeast and East Asian countries where it has been causing serious damage to Cocos nucifera L. This insect also occurs on the Southwest Islands off Kyushu Island in Japan. To evaluate the potential northward range expansion of this insect in Japan, we investigated its cold tolerance at 0, 5, and 10 °C (egg, larva, pupa, and adult), 13 °C (adult), and 15 °C (egg and hatched larva). At 15 °C, few eggs hatched, and the larvae that hatched died within a few days of hatching. At 13 °C, Ltime₉₅ was estimated to be 23 days for adults, with the most cold-tolerant developmental stage at 10 °C. At all developmental stages, Ltime₉₅ of B. longissima was estimated to be 19 days at 10 °C, 8 days at 5 °C, and 5 days at 0 °C, suggesting the cold tolerance of this beetle is very low. Considering average daily temperatures, it is unlikely that B. longissima can establish itself north of Amami-Oshima Island, located in the far south off the main island of Japan.     

Cytoplasmic incompatibility involving <Emphasis Type="Italic">Cardinium</Emphasis> and <Emphasis Type="Italic">Wolbachia</Emphasis> in the white-backed planthopper <Emphasis Type="Italic">Sogatella furcifera</Emphasis> (Hemiptera: Delphacidae)

Cytoplasmic incompatibility (CI) is a reproductive phenotype induced by bacterial endosymbionts in arthropods. Measured as a reduction in egg hatchability resulting from the crossing of uninfected females with bacteria-infected males, CI increases the frequency of bacteria-infected hosts by restricting the fertilization opportunities of uninfected hosts in populations. Wolbachia, a type of alpha-proteobacteria, is well known as a CI inducer in a wide range of arthropod species, while Cardinium, a member of the phylum Bacteroidetes, is known to cause CI in one wasp and three spider mite species. In this study, dual infection with Cardinium and Wolbachia induced strong CI in a single host, Sogatella furcifera (Horváth), a planthopper species that is naturally infected with both bacteria. Specifically, infection with Cardinium alone was found to cause a 76 % reduction in egg development, and dual infection with Cardinium and Wolbachia a 96 % reduction, indicating that Cardinium induces CI and the dual infection raises the CI level. This study was the first to document reproductive alteration by Cardinium in a diploid host species.     

Spatial and Temporal Resource Use by Feral and Abandoned Dogs

We compared spatial and temporal patterns of resource use by feral and abandoned domestic dogs (Canis familiaris) on the Navajo reservation in Arizona and New Mexico. Community dumps provide locally abundant food resources utilized both by feral dogs and dogs abandoned at the dump site. Although population parameters were much the same for feral and abandoned dogs, the use of space varied distinctly and reflected behavioral differences in the way each population responded to the absence of human control, the need to acquire food, and the developmental state of pups. Temporal use of resources by feral dogs varied seasonally with the age of pups in one pack, but not in a second pack. Priority of access to local resources may be influenced by aggressive interactions among dogs at a dump. Barking may serve to warn dogs already present at a dump that competitors have arrived.     

Mineralization of Surfactants by Microbiota of Aquatic Plants

The biodegradation of linear alkylbenzene sulfonate (LAS) and linear alcohol ethoxylate (LAE) by the microbiota associated with duckweed (Lemna minor) and the roots of cattail (Typha latifolia) was investigated. Plants were obtained from a pristine pond and a pond receiving wastewater from a rural laundromat. Cattail roots and duckweed plants were incubated in vessels containing sterile water amended with [¹⁴C]LAS, [¹⁴C]LAE, or ¹⁴C-labeled mixed amino acids (MAA). Evolution of ¹⁴CO₂ was determined over time. The microbiota of cattail roots from both ponds mineralized LAS, LAE, and MAA without lag periods, and the rates and extents of mineralization were not significantly affected by the source of the plants. Mineralization of LAS and LAE was more rapid in the rhizosphere than in nearby root-free sediments, which exhibited differences as a function of pond. The microbiota of duckweed readily mineralized LAE and MAA but not LAS. The rate and extent of mineralization were not affected by the source of the duckweed.     

Functional role of R462 in the degradation of hyaluronan catalyzed by hyaluronate lyase from <Emphasis Type="Italic">Streptococcus pneumoniae</Emphasis>

Hyaluronan lyase from Streptococcus pneumoniae can degrade hyaluronic acid, which is one of the major components in the extracellular matrix. Hyaluronan can regulate water balance, osmotic pressure, and act as an ion exchange resin. Followed by our recent work on the catalytic reaction mechanism and substrate binding mode, we in this work further investigate the functional role of active site arginine residue, R462, in the degradation of hyaluronan. The site directed mutagenesis simulation of R462A and R462Q were modeled using a combined quantum mechanical and molecular mechanical method. The overall substrate binding features upon mutations do not have significant changes. The energetic profiles for the reaction processes are essentially the same as that in wild type enzyme, but significant activation barrier height changes can be observed. Both mutants were shown to accelerate the overall enzymatic activity, e.g., R462A can reduce the barrier height by about 2.8 kcal mol^–1, while R462Q reduces the activation energy by about 2.9 kcal mol^–1. Consistent with the active site model calculated using density functional theory, our results can support that the positive charge on R462 guanidino side chain group plays a negative role in the catalysis. Finally, the functional role of R462 was proposed to facilitate the formation of initial enzyme-substrate complex, but not in the subsequent catalytic degradation reaction.

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Graphical Abstract Degradation of hyaluronan catalyzed by hyaluronate lyase from Streptococcus pneumoniae

     

The high diversity of <Emphasis Type="Italic">Lotus corniculatus</Emphasis> endosymbionts in soils of northwest Spain

The diversity of rhizobia that establish symbiosis with Lotus corniculatus has scarcely been studied. Several species of Mesorhizobium are endosymbionts of this legume, including Mesorhizobium loti, the type species of this genus. We analysed the genetic diversity of strains nodulating Lotus corniculatus in Northwest Spain and ten different RAPD patterns were identified among 22 isolates. The phylogenetic analysis of the 16S rRNA gene showed that the isolated strains belong to four divergent phylogenetic groups within the genus Mesorhizobium. These phylogenetic groups are widely distributed worldwide and the strains nodulate L. corniculatus in several countries of Europe, America and Asia. Three of the groups include the currently described Mesorhizobium species M. loti, M. erdmanii and M. jarvisii which are L. corniculatus endosymbionts. An analysis of the recA and atpD genes showed that our strains belong to several clusters, one of them very closely related to M. jarvisii and the remanining ones phylogenetically divergent from all currently described Mesorhizobium species. Some of these clusters include L. corniculatus nodulating strains isolated in Europe, America and Asia, although the recA and atpD genes have been sequenced in only a few L. corniculatus endosymbionts. The results of this study revealed great phylogenetic diversity of strains nodulating L. corniculatus, allowing us to predict that even more diversity will be discovered as further ecosystems are investigated.     

ATGL and CGI-58 are lipid droplet proteins of the hepatic stellate cell line HSC-T6

Lipid droplets (LDs) of hepatic stellate cells (HSCs) contain large amounts of vitamin A [in the form of retinyl esters (REs)] as well as other neutral lipids such as TGs. During times of insufficient vitamin A availability, RE stores are mobilized to ensure a constant supply to the body. To date, little is known about the enzymes responsible for the hydrolysis of neutral lipid esters, in particular of REs, in HSCs. In this study, we aimed to identify LD-associated neutral lipid hydrolases by a proteomic approach using the rat stellate cell line HSC-T6. First, we loaded cells with retinol and FAs to promote lipid synthesis and deposition within LDs. Then, LDs were isolated and lipid composition and the LD proteome were analyzed. Among other proteins, we found perilipin 2, adipose TG lipase (ATGL), and comparative gene identification-58 (CGI-58), known and established LD proteins. Bioinformatic search of the LD proteome for α/β-hydrolase fold-containing proteins revealed no yet uncharacterized neutral lipid hydrolases. In in vitro activity assays, we show that rat (r)ATGL, coactivated by rat (r)CGI-58, efficiently hydrolyzes TGs and REs. These findings suggest that rATGL and rCGI-58 are LD-resident proteins in HSCs and participate in the mobilization of both REs and TGs.     

Towards a Supertree of Arthropoda: A Species-Level Supertree of the Spiny,Slipper and Coral Lobsters (Decapoda: Achelata)

While supertrees have been built for many vertebrate groups (notably birds, mammals and dinosaurs), invertebrates have attracted relatively little attention. The paucity of supertrees of arthropods is particularly surprising given their economic and ecological importance, as well as their overwhelming contribution to biodiversity. The absence of comprehensive archives of machine-readable source trees, coupled with the need for software implementing repeatable protocols for managing them, has undoubtedly impeded progress. Here we present a supertree of Achelata (spiny, slipper and coral lobsters) as a proof of concept, constructed using new supertree specific software (the Supertree Toolkit; STK) and following a published protocol. We also introduce a new resource for archiving and managing published source trees. Our supertree of Achelata is synthesised from morphological and molecular source trees, and represents the most complete species-level tree of the group to date. Our findings are consistent with recent taxonomic treatments, confirming the validity of just two families: Palinuridae and Scyllaridae; Synaxidae were resolved within Palinuridae. Monophyletic Silentes and Stridentes lineages are recovered within Palinuridae, and all sub-families within Scyllaridae are found to be monophyletic with the exception of Ibacinae. We demonstrate the feasibility of building larger supertrees of arthropods, with the ultimate objective of building a complete species-level phylogeny for the entire phylum using a divide and conquer strategy.