Comparative analysis of methane-oxidizing archaea and sulfate-reducing bacteria in anoxic marine sediments

The oxidation of methane in anoxic marine sediments is thought to be mediated by a consortium of methane-consuming archaea and sulfate-reducing bacteria. In this study, we compared results of rRNA gene (rDNA) surveys and lipid analyses of archaea and bacteria associated with methane seep sediments from several different sites on the Californian continental margin. Two distinct archaeal lineages (ANME-1 and ANME-2), peripherally related to the order Methanosarcinales, were consistently associated with methane seep marine sediments. The same sediments contained abundant (13)C-depleted archaeal lipids, indicating that one or both of these archaeal groups are members of anaerobic methane-oxidizing consortia. (13)C-depleted lipids and the signature 16S rDNAs for these archaeal groups were absent in nearby control sediments. Concurrent surveys of bacterial rDNAs revealed a predominance of delta-proteobacteria, in particular, close relatives of Desulfosarcina variabilis. Biomarker analyses of the same sediments showed bacterial fatty acids with strong (13)C depletion that are likely products of these sulfate-reducing bacteria. Consistent with these observations, whole-cell fluorescent in situ hybridization revealed aggregations of ANME-2 archaea and sulfate-reducing Desulfosarcina and Desulfococcus species. Additionally, the presence of abundant (13)C-depleted ether lipids, presumed to be of bacterial origin but unrelated to ether lipids of members of the order Desulfosarcinales, suggests the participation of additional bacterial groups in the methane-oxidizing process. Although the Desulfosarcinales and ANME-2 consortia appear to participate in the anaerobic oxidation of methane in marine sediments, our data suggest that other bacteria and archaea are also involved in methane oxidation in these environments.     

Molecular variation among Chinese and global winter faba bean germplasm

A sample of winter faba bean germplasm from China was compared with germplasm from outside China, using AFLP analyses. Both sets of germplasm were obtained from the National Genebank of China, Institute of Crop Sciences (ICS), Chinese Academy of Agricultural Sciences, Beijing, China. A sample of 39 winter type accessions from outside of China and 204 Chinese landraces and varieties (201 winter types and 3 spring types) were characterized with 10 AFLP primers. These detected 266 polymorphic bands. The Chinese germplasm was clearly separated from the rest of the world in principal component analysis and clustering analysis, with the spring types from China showing the greatest separation. Yunnan germplasm, both landraces and commercial varieties, showed the greatest separation among the germplasm of Chinese winter faba bean provinces. The landraces/varieties from Anhui, Zhejiang, Sichuan, Jianxi, Guizhou and Fujian provinces clustered in a central group. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Respiration during Postharvest Development of Soursop Fruit, Annona muricata L

Fruit of soursop, Annona muricata L., showed increased CO₂ production 2 days after harvest, preceding the respiratory increase that coincided with autocatalytic ethylene evolution and other ripening phenomena. Experiments to alter gas exchange patterns of postharvest fruit parts and tissue cylinders had little success.

The respiratory quotient of tissue discs was near unity throughout development. 2,4-Dinitrophenol uncoupled respiration more effectively than carbonylcyanide m-chlorophenylhydrazone; 0.4 millimolar KCN stimulated, 4 millimolar salicylhydroxamic acid slightly inhibited, and their combination strongly inhibited respiration, as did 10 millimolar NaN₃. Tricarboxylic acid cycle members and ascorbate were more effective substrates than sugars, but acetate and glutarate strongly inhibited.

Disc respiration showed the same early peak as whole fruit respiration; this peak is thus an inherent characteristic of postharvest development and cannot be ascribed to differences between ovaries of the aggregatetype fruit. The capacity of the respiratory apparatus did not change during this preclimacteric peak, but the contents of rate-limiting malate and citrate increased after harvest.

It is concluded that the preclimacteric rise in CO₂ evolution reflects increased mitochondrial respiration because of enhanced supply of carboxylates as a substrate, probably induced by detachment from the tree. The second rise corresponds with the respiration during ripening of other climacteric fruits.

     

Microhabitat use by mountain pygmy‐possum (Burramys parvus): Implications for the conservation of small mammals in alpine environments

The Australian alpine region harbours a wide range of species, many of which are endemic and of high conservation value. Among these species, the endangered mountain pygmy‐possum, Burramys parvus, is of particular interest because this specialized marsupial is highly sensitive to extreme temperatures. The selection of microhabitats by B. parvus is a critical but poorly understood element of its biological characteristics. To understand the microhabitat preferences of B. parvus, we performed detailed investigations of the thermal properties of alpine boulder fields. The selection of a preferred microclimate was demonstrated by comparing temperatures and environmental conditions in preferred and non‐preferred boulder fields. The variability of the daily temperature depended on the depth at which measurements were made within the boulder fields. Temperatures were more stable as depth increased. The results suggest that B. parvus prefers to occupy deep boulder fields at high elevations with good rock structure (small rock and cavity size with multiple layers) and long snow duration because these boulder fields can provide a favourable microclimate. At 1 m depth, the maximum temperatures in the hottest part of the year were 1.27°C cooler in preferred compared to non‐preferred boulder fields. In the coldest part of the year, immediately following the melting of persistent snow cover, the minimum temperatures at a depth of 1 m were 1.67°C warmer in preferred compared to non‐preferred boulder fields. On average, the snow duration was 27 days greater in the boulder fields preferred by B. parvus than in non‐preferred boulder fields. Our results emphasize the value of boulder field microhabitats as thermal refuges for small mammals in rocky habitats within alpine environments in the light of continuing habitat loss and climate change.     

Neuropeptide-Y and ACTH-immunoreactive innervation of corticotropin releasing factor (CRF)-synthesizing neurons in the hypothalamus of the rat

Summary Corticotropin releasing factor (CRF), synthesized in neurons of the hypothalamic paraventricular nucleus (PVN), is one of the main regulators of the pituitaryadrenal cortex endocrine axis. In order to elucidate the possible involvement of the central neuropeptide-Y (NPY)-and adrenocorticotroph hormone (ACTH)-immunoreactive (IR) systems in the innervation of hypophysiotrophic CRF-synthesizing neurons, immunocytochemical double labelling studies were conducted in the hypothalamus of the rat to localize CRF-synthesizing neurons, as well as neuronal fibers exhibiting NPY and ACTH-immunoreactivity, respectively.The parvocellular subnuclei of the PVN received an intense NPY-and ACTH-IR innervation. At the light microscopic level, these peptidergic axons were associated with the dendrites and perikarya of CRF-IR neurons. Ultrastructural analysis revealed that NPY- and ACTH-IR axons established synaptic specializations with parvocellular neurons expressing CRF-immunoreactivity. These findings indicate that both neuropeptide-Y and adrenocorticotroph hormone containing neuronal systems of the brain are capable of influencing adrenal function via synaptic interactions with hypophysiotrophic CRF-synthesizing neurons. The data also support the concept that NPY and ACTH might be ntilized as neuromodulators within the PVN.Dedicated to Professor Dr. T.H. Schiebler on the occasion of his 65th birthday     

Natural variation for Fe-efficiency is associated with upregulation of Strategy I mechanisms and enhanced citrate and ethylene synthesis in Pisum sativum L.

Iron (Fe)-deficiency is a common abiotic stress in Pisum sativum L. grown in many parts of the world. The aim of the study was to investigate variation in tolerance to Fe deficiency in two pea genotypes, Santi (Fe-efficient) and Parafield (Fe-inefficient). Fe deficiency caused greater declines in chlorophyll score, leaf Fe concentration and root-shoot development in Parafield compared to Santi, suggesting greater Fe-efficiency in Santi. Fe chelate reductase activity and ethylene production were increased in the roots of Santi and to a lesser extent in Parafield under Fe deficiency, while proton extrusion was only occurred in Santi. Moreover, expression of the Fe chelate reductase gene, FRO1, and Fe transporter, RIT1 were upregulated in Fe-deficient roots of Santi. Expression of HA1 (proton extrusion) was also significantly higher in Santi when compared to Parafield grown in Fe-deficient conditions. Furthermore, the application of the ethylene biosynthesis inhibitor, 1-aminoisobutyric acid reduced the Fe chelate reductase activity, supporting a direct role for ethylene in its induction. A significant increase in root citrate was only observed in Santi under Fe deficiency indicating a role for citrate in the Fe-efficiency mechanism. Taken together, our physiological and molecular data indicate that genotypic variation in tolerance to Fe deficiency in Santi and Parafield plants is a result of variation in a number of Strategy I mechanisms and also suggest a direct role for ethylene in Fe reductase activity. The pea cultivar, Santi provides a new source of Fe-efficiency that can be exploited to breed more Fe-efficient peas.     

Escape from parasitoids leave larvae vulnerable to predators and has unexpected outcomes for pest suppression

It is well recognised that interactions among multiple species of natural enemies can have important consequences for the population dynamics of the species involved, particularly when intra-guild predation (IGP) occurs. However, these interactions are highly dependent on the type and behaviour of the prey, an aspect of IGP that is frequently overlooked. Here we demonstrate how a parasitoid (Dolichogenidea tasmanica) facilitates attack on a lepidopteran larva (Epiphyas postvittana) by a predatory mite (Anystis baccarum). We show that anti-predator behaviour of the lepidopteran larva is the mechanism that facilitates this. E. postvittana is protected by its silken leaf roll which limits predation by the mite except when the larva is attacked by the parasitoid causing the larva to leave its shelter. We explored the implications of the interactions among these three species for pest suppression by modelling changes in mite density and mite predation intensity. The presence of mites (the IG predator) always leads to a decrease in ability of the parasitoid to control E. postvittana and, as mite predation intensity increases, the ability of the parasitoid to suppress E. postvittana decreases. The results from the experiment show a synergistic interaction, but results from the population model show an interaction resulting in pest release. These findings support the general idea that if uni-directional IGP occurs, and competition is strong between the top and intermediate predator, then a single best control agent will likely be more effective at suppressing the prey population than multiple control agents combined. These findings have important implications for the management of E. postvittana in vineyards across Southern Australia and for other multi-species systems.     

Collaboration of Werner syndrome protein and BRCA1 in cellular responses to DNA interstrand cross-links

Cells deficient in the Werner syndrome protein (WRN) or BRCA1 are hypersensitive to DNA interstrand cross-links (ICLs), whose repair requires nucleotide excision repair (NER) and homologous recombination (HR). However, the roles of WRN and BRCA1 in the repair of DNA ICLs are not understood and the molecular mechanisms of ICL repair at the processing stage have not yet been established. This study demonstrates that WRN helicase activity, but not exonuclease activity, is required to process DNA ICLs in cells and that WRN cooperates with BRCA1 in the cellular response to DNA ICLs. BRCA1 interacts directly with WRN and stimulates WRN helicase and exonuclease activities in vitro. The interaction between WRN and BRCA1 increases in cells treated with DNA cross-linking agents. WRN binding to BRCA1 was mapped to BRCA1 452–1079 amino acids. The BRCA1/BARD1 complex also associates with WRN in vivo and stimulates WRN helicase activity on forked and Holliday junction substrates. These findings suggest that WRN and BRCA1 act in a coordinated manner to facilitate repair of DNA ICLs.     

Involvement of human MOF in ATM function

We have determined that hMOF, the human ortholog of the Drosophila MOF gene (males absent on the first), encoding a protein with histone acetyltransferase activity, interacts with the ATM (ataxia-telangiectasia-mutated) protein. Cellular exposure to ionizing radiation (IR) enhances hMOF-dependent acetylation of its target substrate, lysine 16 (K16) of histone H4 independently of ATM function. Blocking the IR-induced increase in acetylation of histone H4 at K16, either by the expression of a dominant negative mutant DeltahMOF or by RNA interference-mediated hMOF knockdown, resulted in decreased ATM autophosphorylation, ATM kinase activity, and the phosphorylation of downstream effectors of ATM and DNA repair while increasing cell killing. In addition, decreased hMOF activity was associated with loss of the cell cycle checkpoint response to DNA double-strand breaks. The overexpression of wild-type hMOF yielded the opposite results, i.e., a modest increase in cell survival and enhanced DNA repair after IR exposure. These results suggest that hMOF influences the function of ATM.     

Frontiers in climate change-disease research

The notion that climate change will generally increase human and wildlife diseases has garnered considerable public attention, but remains controversial and seems inconsistent with the expectation that climate change will also cause parasite extinctions. In this review, we highlight the frontiers in climate change-infectious disease research by reviewing knowledge gaps that make this controversy difficult to resolve. We suggest that forecasts of climate-change impacts on disease can be improved by more interdisciplinary collaborations, better linking of data and models, addressing confounding variables and context dependencies, and applying metabolic theory to host-parasite systems with consideration of community-level interactions and functional traits. Finally, although we emphasize host-parasite interactions, we also highlight the applicability of these points to climate-change effects on species interactions in general.