What shapes the altitudinal range of a high mountain Mediterranean plant? Recruitment probabilities from ovule to seedling stage

Recruitment is a complex process consisting of sequential stages affected by biotic interactions and abiotic factors. Assessment of these sequential stages and corresponding subprocesses may be useful in identifying the most critical stages. Accordingly, to assess the factors that may determine the altitudinal range limits of the high mountain Mediterranean plant Silene ciliata, a set of demographic stages, from flower production to establishment of 2‐yr‐old plants, and their influence on recruitment probability were examined using a step‐by‐step approach. We integrated florivory, pollination and pre‐dispersal seed predation as pre‐dispersal factors, and seedling emergence and survival as post‐dispersal determinants of recruitment. Three populations were monitored at the southernmost margin of the species along its local altitudinal range. Previous studies suggest that seediness is strongly limited by summer drought especially at the lower boundary of the species, a situation that may worsen under current global warming. Our results showed that recruitment was mainly limited by low seed production in the pre‐dispersal stage and low seedling emergence and survival in the post‐dispersal stage, probably due to environmental harshness in summer. By contrast, biotic factors responsible for propagule loss, such as flower and fruit predation, had a minor effect on the probability of plant recruitment. Although the relative importance of transition probabilities was similar among populations along the altitudinal range, comparatively lower flower production significantly reduced the number of recruited plants at the lowest altitude population. This demographic bottleneck, together with increased competition with other species favoured by climate warming, might collapse population growth and limit persistence at the lower altitudinal range of the species, raising its low local altitudinal edge.     

Five New Guaiane Sesquiterpenes from the Endophytic Fungus Xylaria sp. YM 311647 of Azadirachta indica

Five new guaiane sesquiterpenes, 1 – 5 , were isolated from the culture broth of the endophytic fungus Xylaria sp. YM 311647, isolated from Azadirachta indica A. Juss . The structures of these compounds were elucidated on the basis of spectroscopic analyses, and their inhibitory activities against five pathogenic fungi were evaluated. All guaiane sesquiterpenes showed moderate or weak antifungal activities in a broth microdilution assay.     

Common and rare species respond to similar niche processes in macroinvertebrate metacommunities

Ecologists have long investigated why communities are composed of a few common species and many rare species. Most studies relate rarity to either niche differentiation among species or spatial processes. There is a parallel between these processes and the processes proposed to explain the structure of metacommunities. Based on a metacommunity perspective and on data on stream macroinvertebrates from different regions of Brazil, we answer two questions. 1) Are sets of common and rare species affected by similar niche and spatial processes? 2) How does the community composition of common and of rare species differ? The main hypothesis we test is that common species are mainly affected by environmental factors, whereas rare species are mostly influenced by dispersal limitation. We used variation partitioning to determine the proportion of variation explained by the environment and space in common and rare species matrices. Contrary to our expectations, evidence supported the idea that both common and rare species are affected mainly by environmental factors, even after controlling for the differing information content between common and rare species matrices. Moreover, the abundance of some common species is also a good predictor of variation in rare species matrices. Niche differences are unlikely to be the sole cause of patterns of rarity in these metacommunities. We suggest that sets of common and rare species react to similar major environmental gradients and that rare species also respond to processes that operate at a more fine‐grained spatial scale, particularly biotic interactions. We extend the view that species sorting is the dominant process structuring metacommunities and argue that future studies focusing on rarity would benefit from a metacommunity perspective.     

Cytotoxicity and genotoxicity induced by aflatoxin B1, ochratoxin A,and their combination in cultured Vero cells

Aflatoxin B1 (AFB1) and ochratoxin A (OTA) are important food‐borne mycotoxins that have been implicated in human health. In this study, independent and combinative toxicities of AFB1 and OTA were tested in cultured monkey kidney Vero cells. The experiments reported here were conducted to evaluate the effect of these toxins on cell viability followed by the determination of cell death pathways, using the quantification of DNA fragmentation and the expression of p53 and bcl‐2 protein levels. Our results showed that AFB1 and OTA caused a marked decrease of cell viability in a dose‐dependent manner. Under the same conditions, these mycotoxins increased fragmented DNA levels. In addition, p53 was activated in response to DNA damage and the expression of the antiapoptotic factor bcl‐2 decreased significantly. According to these data, AFB1 and OTA seemed to be involved in an apoptotic process. Moreover, combined AFB1 and OTA induced all the toxicities observed with the mycotoxins separately. Therefore, this combination was classified as an additive response of the two mycotoxins. © 2010 Wiley Periodicals, Inc. J Biochem Mol Toxicol 24:42–50, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/jbt.20310     

Characterization of photodynamic therapy responses elicited in A431 cells containing intracellular organelle‐localized photofrin

Photodynamic therapy (PDT), a photochemotherapeutic regimen used to treat several diseases, including cancer, exerts its effects mainly through induction of cell death. Using human epidermoid carcinoma A431 cells as a model, we previously showed that distinct cell death types could be triggered by protocols that selectively delivered Photofrin (a clinically approved photosensitizer) to different subcellular sites (Hsieh et al. [2003] J Cell Physiol 194: 363–375]. Here, the responses elicited by PDT in A431 cells containing intracellular organelle‐localized Photofrin were further characterized. Two prominent cell phenotypes were observed under these conditions: one characterized by perinuclear vacuole (PV) formation 2–8 h after PDT followed by cell recovery or shrinkage within 48 h, and a second characterized by typical apoptotic features appearing within 4 h after PDT. DCFDA‐sensitive reactive oxygen species formed proximal to PVs during the response to PDT, covering areas in which both endoplasmic reticulum (ER) and the Golgi complex were located. Biochemical analyses showed that Photofrin‐PDT also induced JNK activation and altered the protein secretion profile. A more detailed examination of PV formation revealed that PVs were derived from the ER. The alteration of ER structure induced by PDT was similar to that triggered by thapsigargin, an ER Ca²⁺‐ATPase inhibitor that perturbs Ca²⁺ homeostasis, suggesting a role for Ca²⁺ in the formation of PVs. Microtubule dynamics did not significantly affect PV formation. This study demonstrates that cells in which intracellular organelles are selectively loaded with Photofrin mount a novel response to ER stress induced by PDT. J. Cell. Biochem. 111: 821–833, 2010. © 2010 Wiley‐Liss, Inc.     

Comprehensive proteome profiling of the Fe(III)‐reducing myxobacterium Anaeromyxobacter dehalogenans 2CP‐C during growth with fumarate and ferric citrate

Anaeromyxobacter dehalogenans is a microaerophilic member of the delta‐proteobacteria which is able to utilize a wide range of electron acceptors, including halogenated phenols, U(VI), Fe(III), nitrate, nitrite, oxygen and fumarate. To date, the knowledge regarding general metabolic activities of this ecologically relevant bacterium is limited. Here, we present a first systematic 2‐D reference map of the soluble A. dehalogenans proteome in order to provide a sound basis for further proteomic studies as well as to gain first global insights into the metabolic activities of this bacterium. Using a combination of 2‐DE and MALDI‐TOF‐MS, a total of 720 proteins spots were identified, representing 559 unique protein species. Using the proteome data, altogether 50 metabolic pathways were found to be expressed during growth with fumarate as primary electron acceptor. An analysis of the pathways revealed an extensive display of enzymes involved in the catabolism and anabolism of a variety of amino acids, including the unexpected fermentation of lysine to butyrate. Moreover, using the reference gel as basis, a semi‐quantitative analysis of protein expression changes of A. dehalogenans during growth with ferric citrate as electron acceptor was conducted. The adaptation to Fe(III) reducing conditions involved the expression changes of a total of 239 proteins. The results suggest that the adaptation to Fe(III) reductive conditions involves an increase in metabolic flux through the tricarboxylic acid cycle, which is fueled by an increased catabolism of amino acids.     

A new genus of African Acrometopini (Tettigoniidae: Phaneropterinae) based on morphology,chromosomes, acoustics,distribution, and molecular data,and the description of a new species

A new genus, Altihoratosphaga, is erected for species formerly assigned to Horatosphaga Schaum, 1853, and a new species is described. Four species are included in Altihoratosphaga: Altihoratosphaga nomima (Karsch, 1896), Altihoratosphaga montivaga ( Sjöstedt, 1909 ), Altihoratosphaga nou (Hemp, 2007) and Altihoratosphaga hanangensis sp. nov. All four species are restricted to Tanzanian localities, and, except for A. nomima, for which no ecological data are available, are confined to montane forest habitats. Data on ecology, acoustics, chromosomes, and molecular relationships are provided, as well as a key to Altihoratosphaga species. The present‐day distribution of Altihoratosphaga species suggests former migration events at times when wetter and colder climatic fluctuations favoured connections between montane forest communities, which today are isolated, enabling flightless taxa such as Altihoratosphaga and Monticolaria to spread. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 158 , 66–82.     

Life‐history variability of non‐native centrarchids in regulated river systems of the lower River Guadiana drainage (south‐west Iberian Peninsula)

Life‐history variability of two non‐native centrarchids, pumpkinseed Lepomis gibbosus and largemouth bass Micropterus salmoides, was evaluated in three stream stretches of the lower River Guadiana drainage (south‐west Iberian Peninsula) with different degrees of regulated flows. Abundance, condition and population structure differed among populations for both species, but invasion success was lower in the least regulated river. Lepomis gibbosus were abundant and had multiple age classes in the three river sites, whereas M. salmoides were less abundant and mainly represented by young‐of‐the‐year fish. Juvenile growth in L. gibbosus was similar in all three populations, though longevity was slightly greater in the population from the River Guadiana mainstream. Lepomis gibbosus exhibited a long reproductive season, but the duration of season, size at maturity and reproductive effort varied among populations. The life‐history differences found demonstrate the importance of species adaptation to local conditions which might favour their invasion success. Lepomis gibbosus were more adaptable and resilient to local conditions, whereas M. salmoides seemed dependent on reservoirs and large rivers for maintenance of riverine populations.     

The SciZ protein anchors the enteroaggregative Escherichia coli Type VI secretion system to the cell wall

Type VI secretion systems (T6SS) are multi‐component machines encoded within the genomes of most Gram‐negative bacteria that associate with plant, animal and/or human cells, and therefore are considered as potential virulence factors. We recently launched a study on the Sci‐1 T6SS of enteroaggregative Escherichia coli (EAEC). The Sci‐1 T6SS is composed of all or a subset of the 21 gene products encoded within the cluster, 13 of which are shared by all T6SS identified so far. In the present work, we focussed our attention on the SciZ protein. We first showed that SciZ is required for the release of the Hcp protein in the culture supernatant and for efficient biofilm formation, demonstrating that SciZ is necessary for EAEC T6SS function. Indeed, SciZ forms a complex with SciP, SciS and SciN, three core components of the transport apparatus. Fractionation and topology studies showed that SciZ is a polytopic inner membrane protein with three trans‐membrane segments. Computer analyses identified a motif shared by peptidoglycan binding proteins of the OmpA family in the SciZ periplasmic domain. Using in vivo and in vitro binding assays, we showed that this motif anchors the SciZ protein to the cell wall and is required for T6SS function.