Temporal Dynamics of River Biofilm in Constant Flows: A Case Study in a Riverside Laboratory Flume

A 15‐week experiment was performed in a riverside laboratory flume (with diverted river water) to check variations of river biofilm structure (biomass, algal and bacterial compositions) and function (community gross primary production GPP and respiration) under constant flow while water quality went through natural temporal variations. One major suspended matter pulse coinciding with one river flood was recorded after 10 weeks of experiment. Epilithic biofilm first exhibited a 10‐week typical pattern of biomass accrual reaching 33 g ash‐free dry matter (AFDM) m^–2 and 487 mg chlorophyll‐a m^–2 and then, experienced a shift to dominance of loss processes (loss of 60% AFDM and 80% chlorophyll‐a) coinciding with the main suspended matter pulse. Algal diversity remained low and constant during the experiment: Fragilaria capucina and Encyonema minutum always contribute over 80% of cell counts. DGGE banding patterns discriminated between two groups that corresponded to samples before and after biomass loss, indicating major changes in the bacterial community composition. GPP/R remained high during the experiment, suggesting that photoautotrophic metabolism prevailed and detachment was not autogenic (i.e., due to algal senescence or driven by heterotrophic processes within the biofilm). Observational results suggested that silt deposition into the biofilm matrix could have triggered biomass loss. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Immunohistochemical analysis and 3D reconstruction of the cephalic nervous system in Chaetognatha: insights into the evolution of an early bilaterian brain?

Abstract. We examined the brain architecture in different species of Chaetognatha using immunofluorescence methods with a set of nervous system markers and confocal laser-scan microscopic analysis. These markers include antibodies against synaptic proteins, RFamide-related peptides, and tyrosinated tubulin, as well as a marker of cell nuclei. Furthermore, we present a 3D reconstruction based on histological section series. Our results expand the previous knowledge on neuroanatomy in Chaetognatha. We suggest a structural and functional subdivision of the rather complex chaetognath brain into two domains, a posterior domain that may be primarily involved in the integration of sensory input, and an anterior domain that may be involved in the control of the mouthparts and the anterior part of the digestive system. Immunolocalization of a neuropeptide suggests the presence of an identifiable group of neurons associated with the brain of all species examined here. However, our data also reveal a certain degree of interspecific variation and divergence within the Chaetognatha concerning, for example, the pattern of nerves branching off the brain and the proportional sizes of the various neuropil compartments. We compare our data to brain architecture in various other representatives of Protostomia and Deuterostomia. The chaetognath brain fits within the range of structural variation encountered in protostomian brains, and we cannot find any brain characteristics that would argue in favor of placing chaetognaths outside of the Protostomia. Rather, we see the circumoral arrangement of their cephalic nervous system as an argument that suggests protostome affinities.     

Gene expression changes related to the production of phenolic compounds in potato tubers grown under drought stress

Polyphenols represent a large family of plant secondary metabolites implicated in the prevention of various diseases such as cancers and cardiovascular diseases. The potato is a significant source of polyphenols in the human diet. In this study, we examined the expression of thirteen genes involved in the biosynthesis of polyphenols in potato tubers using real-time RT-PCR. A selection of five field grown native Andean cultivars, presenting contrasting polyphenol profiles, was used. Moreover, we investigated the expression of the genes after a drought exposure. We concluded that the diverse polyphenolic profiles are correlated to variations in gene expression profiles. The drought-induced variations of the gene expression was highly cultivar-specific. In the three anthocyanin-containing cultivars, gene expression was coordinated and reflected at the metabolite level supporting a hypothesis that regulation of gene expression plays an essential role in the potato polyphenol production. We proposed that the altered sucrose flux induced by the drought stress is partly responsible for the changes in gene expression. This study provides information on key polyphenol biosynthetic and regulatory genes, which could be useful in the development of potato varieties with enhanced health and nutritional benefits.     

Role of host‐plant selection in resistance of wild Solanum species to Macrosiphum euphorbiae and Myzus persicae

Damage to potatoes by Macrosiphum euphorbiae (Thomas) and Myzus persicae (Sulzer) (both Hemiptera: Aphididae) can be controlled through plant resistance. We used ethological experiments and electric penetration graph (EPG) analysis to evaluate the role of host selection in the previously assessed resistance levels of Solanum accessions: Solanum circaeifolium Bitter subsp. capsicibaccatum (Cárdenas) (PI210036), S. chomatophilum Bitter (PI243340 and PI310990), S. okadae Hawkes & Hjert. (PI458367), S. oplocense Hawkes (PI473368), S. pinnatisectum Dunal (PI186553), S. polyadenium Greenm. (PI230463), S. tarijense Hawkes (PI414150), and S. trifidum Correll (PI255538), to M. euphorbiae and M. persicae. Through multivariate analysis, we grouped behavioural variables into factors, which we related to host selection behaviours, and then evaluated whether factors varied between each accession and the susceptible S. tuberosum. None of the factors obtained by ethological experiments differed among accessions. Four of six and three of five factors obtained through EPG varied among accessions for M. euphorbiae and M. persicae, respectively, and were used to suggest resistance characteristics. The resistance to M. persicae of both S. chomatophilum accessions was associated with pathway activity disturbance. Solanum tarijense and S. polyadenium resistance to M. persicae resulted from leaf surface characteristics, which may be trichomes. Solanum oplocense and S. trifidum resistance to M. euphorbiae resulted from the wound response system, whereas S. pinnatisectum resistance may stem from nutritionally unbalanced or toxic phloem sap. Solanum polyadenium resistance to M. euphorbiae was phloem‐based. Solanum circaeifolium ssp. capsicibaccatum resistance to M. persicae, and the resistance of PI243340 S. chomatophilum and S. tarijense to M. euphorbiae were not related to host selection and therefore were presumably due to physiologically active compounds.     

Comparison of Barley Succession and Take-All Disease as Environmental Factors Shaping the Rhizobacterial Community during Take-All Decline

The root disease take-all, caused by Gaeumannomyces graminis var. tritici, can be managed by monoculture-induced take-all decline (TAD). This natural biocontrol mechanism typically occurs after a take-all outbreak and is believed to arise from an enrichment of antagonistic populations in the rhizosphere. However, it is not known whether these changes are induced by the monoculture or by ecological rhizosphere conditions due to a disease outbreak and subsequent attenuation. This question was addressed by comparing the rhizosphere microflora of barley, either inoculated with the pathogen or noninoculated, in a microcosm experiment in five consecutive vegetation cycles. TAD occurred in soil inoculated with the pathogen but not in noninoculated soil. Bacterial community analysis using terminal restriction fragment length polymorphism of 16S rRNA showed pronounced population shifts in the successive vegetation cycles, but pathogen inoculation had little effect. To elucidate rhizobacterial dynamics during TAD development, a 16S rRNA-based taxonomic microarray was used. Actinobacteria were the prevailing indicators in the first vegetation cycle, whereas the third cycle—affected most severely by take-all—was characterized by Proteobacteria, Bacteroidetes, Chloroflexi, Planctomycetes, and Acidobacteria. Indicator taxa for the last cycle (TAD) belonged exclusively to Proteobacteria, including several genera with known biocontrol traits. Our results suggest that TAD involves monoculture-induced enrichment of plant-beneficial taxa.The root disease take-all, caused by the soilborne ascomycete fungus Gaeumannomyces graminis var. tritici, has a significant impact on the global production of wheat and barley (23). Usually, take-all is managed by crop rotation, but low disease levels may also be achieved by monoculture-induced disease suppressiveness (13, 50, 61). Indeed, a spontaneous reduction of disease severity can be observed during wheat or barley monoculture after at least one severe outbreak of the disease, a phenomenon called take-all decline (TAD). Disease symptoms then remain at a low level as long as monoculture continues. TAD is related to the enrichment of certain rhizosphere populations antagonistic to the pathogen (13) and parallel changes in G. graminis var. tritici populations (28).Though TAD is the best-studied example of induced disease suppressiveness (61), knowledge of the mechanisms involved in TAD is fragmentary. Take-all research so far has mainly focused on the role of fluorescent pseudomonads, as they are easy to cultivate and known to be antagonistic to various phytopathogens (21, 35, 62, 63). Several studies have indicated the involvement of other microorganisms in TAD, e.g., Bacillus species and various actinomycetes (3, 26, 45), but none of them has considered the whole bacterial community. Yet, it has been shown that community-based approaches are important in identifying microbial populations potentially involved in suppressiveness (10, 27).The first community-based assessment was carried out based on molecular fingerprinting and sequencing, and it showed that take-all disease of wheat induced changes in several rhizosphere bacterial populations (39). However, disease-suppressive stages were not included. More recently, the taxonomic microarray-based study of Sanguin et al. (48) revealed multiple changes in the rhizobacterial community of wheat when comparing take-all disease and suppressive stages, which paralleled changes in Pseudomonas populations (46). These differences were attributed to TAD, but it is not known whether they occurred as a result of repeated wheat cropping (leading to enrichment of particular bacterial taxa), a disease outbreak and subsequent attenuation (modifying nutrient conditions on roots), or both.Therefore, the objective of this study was to compare the significance of plant succession and take-all disease as environmental factors shaping the rhizobacterial community during TAD. Repeated barley cropping was carried out in microcosms inoculated with G. graminis var. tritici or not inoculated, and the physiologically active bacterial rhizosphere community was monitored using terminal restriction fragment length polymorphism (t-RFLP) (32), as well as microarray analysis of 16S rRNA.     

Fibrotic enzymes modulate wound‐induced skin tumorigenesis

Fibroblasts are a major component of the microenvironment of most solid tumours. Recent research elucidated a large heterogeneity and plasticity of activated fibroblasts, indicating that their role in cancer initiation, growth and metastasis is complex and context‐dependent. Here, we performed genome‐wide expression analysis comparing fibroblasts in normal, inflammatory and tumour‐associated skin. Cancer‐associated fibroblasts (CAFs) exhibit a fibrotic gene signature in wound‐induced tumours, demonstrating persistent extracellular matrix (ECM) remodelling within these tumours. A top upregulated gene in mouse CAFs encodes for PRSS35, a protease capable of collagen remodelling. In human skin, we observed PRSS35 expression uniquely in the stroma of high‐grade squamous cell carcinomas. Ablation of PRSS35 in mouse models of wound‐ or chemically‐induced tumorigenesis resulted in aberrant collagen composition in the ECM and increased tumour incidence. Our results indicate that fibrotic enzymes expressed by CAFs can regulate squamous tumour initiation by remodelling the ECM.     

Community science data suggests that urbanization and forest habitat loss threaten aphidophagous native lady beetles

1. Community scientists have illustrated rapid declines of several aphidophagous lady beetle (Coccinellidae) species. These declines coincide with the establishment of alien coccinellids. We established the Buckeye Lady Beetle Blitz program to measure the seasonal occupancy of coccinellids within gardens across a wide range of landscape contexts. Following the Habitat Compression Hypothesis, we predicted that gardens within agricultural landscapes would be alien‐dominated, whereas captures of natives would be higher within landscapes encompassing a high concentration of natural habitat.
2. Within the state of Ohio, USA, community scientists collected lady beetles for a 7‐day period across 4 years in June and August using yellow sticky card traps. All identifications were verified by professional scientists and beetles were classified by three traits: status (alien or native), mean body length, and primary diet. We compared the relative abundance and diversity of coccinellids seasonally and determined if the distribution of beetles by size, status, and diet was related to landscape features.
3. Alien species dominated the aphidophagous fauna. Native aphidophagous coccinellid abundance was positively correlated with forest habitat while alien species were more common when gardens were embedded within agricultural landscapes. Urbanization was negatively associated with both aphidophagous alien and native coccinellids.
4. Synthesis and Applications: Our census of native coccinellid species within residential gardens—a widespread and understudied habitat—was enabled by volunteers. These data will serve as an important baseline to track future changes within coccinellid communities within this region. We found that native coccinellid species richness and native aphidophagous coccinellid abundance in gardens were positively associated with forest habitat at a landscape scale of 2 km. However, our understanding of when and why (overwintering, summer foraging, or both) forest habitats are important remains unclear. Our findings highlight the need to understand how declining aphidophagous native species utilize forest habitats as a conservation priority.

     

Variations in resistance against Phthorimaea operculella in wild potato tubers

Tuber resistance can contribute to current management strategies against the potato tuber moth, Phthorimaea operculella Zeller (Lepidoptera: Gelechiidae), in field and stored potatoes. Wild potatoes represent a potential source of novel resistance traits against the moth. We assessed resistance in three wild potato species, Solanum multiinterruptum Bitt., Solanum sparsipilum (Bitt.) Juz. & Buk., and Solanum wittmackii Bitt. against neonate and developing tuber moth larvae. All three species had high levels of resistance but accessions of S. sparsipilum and S. wittmackii were significantly more resistant. Resistance in S. multiinterruptum was generally concentrated in the tuber periderm, whereas in S. sparsipilum and S. wittmackii resistance was mainly cortex‐based. Unidentified cortex‐resistance factors in all three species reduced survival and increased larval and pupal development times, but had no apparent effects on the pupal weights of survivors. A high proportion of larvae abandoned or died within tubers of S. wittmackii, which has particularly high levels of unidentified cortex‐based defenses. Resistance decreased in S. multiinterruptum and S. sparsipilum as tubers sprouted but was more stable in S. wittmackii. Periderm‐based resistance was more stable than cortex‐based resistance in S. multiinterruptum during sprouting. In contrast, cortex‐based resistance was stable in tubers of S. wittmackii as these sprouted, and resistance may have increased on some older sprouting tubers. Solanum multiinterruptum and S. sparsipilum are proposed as potential sources of resistance against the potato tuber moth.