The effect of soil phosphorus on the external mycelium growth of arbuscular mycorrhizal fungi during the early stages of mycorrhiza formation

The effects of soil P amendments and time of application on the formation of external mycelium by different arbuscular mycorrhizal (AM) fungi were studied. In the first experiment the external mycelium produced in the soil by the AM fungus Glomus etunicatum Beck. and Gerd., during the early stages of root colonization (7 and 14 days after inoculation), was quantified by the soil-agar film technique. A Brazilian Oxisol was used with three different phosphate levels, varying from deficient to supra-optimal for the plant. Significant differences were observed in the phosphate and inoculation treatments for plant dry weight, P content in the tissue, root length and root colonization, at fourteen days after planting. At 7 days, mycelium growth, root colonization and their relationship were reduced at supra-optimal P concentrations. Applications of P one week after planting reduced mycelium growth and root colonization more than when applied to the soil before planting. In a second experiment the arbuscular mycorrhizal (AM) fungi, Scutellospora heterogama (Nicol. and Gerd.) Walker and Sanders and E3 were tested and compared with Glomus etunicatum. For the species studied, the length of external hyphae per unit of colonized root length was affected by small P additions but no further significant differences were observed at high P levels. The three AM endophytes showed marked differences in their response to P in the soil: Scutellospora heterogama, although producing external mycelium more profusely than the Glomus spp., showed a higher sensitivity to soil P supply.     

Partition behaviour of horseradish peroxidase isoenzymes in aqueous two-phase poly(ethyleneglycol)/phosphate systems

Summary Partition of purified horseradish peroxidase isoenzymes in aqueous two-phase systems was not affected by pH changes, but tie-line length and NaCl addition greatly increased the partition coefficient of all three isoenzymes, the former having more influence than the latter. In all systems, K were higher for acidic than those for neutral and basic isoenzymes, and K for basic were the lowest.     

Structural characterization and promoter activity analysis of the γ-kafirin gene from sorghum

A genomic clone encoding the γ-kafirin gene from sorghum was isolated and sequenced. A 2938 bp sequenced fragment includes an intronless open reading frame of 636 nucleotides encoding a putative polypeptide of 212 amino acids. Comparison of the deduced amino acid sequence of γ-kafirin with the published sequences of γ-prolamins of maize, and Coix revealed highly conserved domains. The N-terminal region of these proteins contains the conserved hexapeptide PPPVHL, which is repeated eight times in γ-zein, four times in γ-kafirin and three times in γ-coixin. The number of PPPVHL repeats accounts predominantly for the differences in the molecular weights of γ-prolamins. Several putative regulatory sequences common to the γ-kafirin and γ-zein genes were identified in both the 5′ and the 3′ flanking regions. Putative GCN4-like regulatory sequences were found at positions ?192 and ?476 in the 5′ flanking region of γ-kafirin. In the 3′ noncoding region, three putative polyadenylation signals, two AATAAT and one AATGAA, were found at positions + 658, + 716, and + 785, respectively. In order to investigate the role of the putative GCN4-like motifs and other possible cis-acting element(s) of the γ-kafirin promoter, a series of deleted and chimeric promoter constructs were introduced into maize, Coix and sorghum tissues by particle bombardment. Histochemical analysis of β-glucuronidase (GUS) activity in different tissues indicated that the element(s) responsible for tissue specificity is probably located in the 285-bp proximal region of the promoter, while the remaining promoter sequence seems to carry the element(s) responsible for the quantitative response.     

Combined effect of ambient temperature and solar radiation on maned sloths' behaviour and detectability

Changes in ambient temperature and solar radiation may affect sloths' metabolic rate and body temperature, with consequent changes in activities, postures and microhabitat selection. Although the separate effect of temperature and solar radiation on sloth's behaviour have been previously studied, the combined effect of these climatic factors on behavioural aspects of sloths has never been systematically evaluated in field conditions. Here we evaluated the influence of hourly ambient temperature variation on maned sloth (Bradypus torquatus) activities, postures and tree crown positions, under sunny and cloudy conditions; and tested if any of the animal posture and position increase their exposure to human detection. We performed 350 h of visual observation on eight maned sloths, equipped with radio-backpacks, in northern Bahia, Brazil, recording their activities, and their resting postures and positions on tree crowns. We also recorded the time taken to visualize the sloths on 58 days to analyse if sloths' detection is affected by posture and position. Higher ambient temperature, within a range of 21–33°C, increased the sloths' activity levels in cloudy conditions but reduced their activity in sunny conditions. Increasing ambient temperature also reduced the frequency of huddled posture and increased the frequency of extended posture and permanence in the inner tree crown. Lastly, the postures and positions did not influence sloths' detectability. Thus, the direction of the temperature–activity relationship depends on climatic conditions (sunny/cloudy), and individuals rely on resting postures and positions to thermoregulate. The warmer and drier future climate, expected to occur in the northern Atlantic Forest, may impose change in the diurnal activity levels and postural pattern for this threatened species, leading maned sloths to reduce its activity on sunny and warmer days and adopting an extended posture.     

Ontogenetic trajectories and early shape differentiation of treehopper pronota (Hemiptera: Membracidae)

Membracids (family: Membracidae), commonly known as treehoppers, are recognizable by their enlarged and often elaborated pronota. Much of the research investigating the development and evolution of this structure has focused on the fifth instar to adult transition, in which the pronotum undergoes the largest transformation as it takes on adult identity. However, little is known about the earlier nymphal stages, the degree to which the pronotum develops at these timepoints, and how development has changed relative to the ancestral state. Here, we studied the nymphal stages and adults of five morphologically distinct membracid species and of Aetalion reticulatum (family: Aetalionidae), the outgroup which was used as an ancestral state proxy. We found that shape differentiation in the pronotum of membracids can start as early as the second instar stage. Most shape differentiation occurs within the nymphal stages and not in the embryo since the shape of the first-instar pronotum did not differ from the outgroup species in all but one species we investigated. We found the anterior–posterior axis of the pronotum elongated at a faster relative rate in membracid species than in A. reticulatum, which contributed to the development of exaggerated pronotal size. Finally, we found differences in the morphogenesis of shape across species. We suggest this is due to the developmental and evolutionary divergence of differential growth patterning of the dorsal surface of the pronotum, not only across species, but also between stages within the same species. This lability may contribute to the evolvability and diversification of the membracid pronotum.     

PHYLOGENETIC INTERRELATIONSHIPS AND REDUCTIVE EVOLUTION IN NEOTROPICAL CHARACIDIIN FISHES (CHARACIFORMES, OSTARIOPHYSI)

Abstract— Miniaturization, which results in the presence of numerous apparently paedomorphic characters associated with reduced size, is a common phenomenon among neotropical fishes, with over 85 miniature species distributed among the five major ordinal groups. Eleven species are recognized as miniatures within the Characidiinae, a monophyletic subunit of Characiformes. A reconstruction of characidiin phylogeny is used to analyze the history of miniaturization events. Former hypotheses of origin of miniaturization among characidiins are rejected, underscoring the need for phylogenetic frameworks in the study of ontogenetic changes associated with the phenomenon of miniaturization. The 11 instances of miniature species can be most parsimoniously attributed to three independent miniaturization events within the Characidiinae.
Reductive characters comprise a large proportion of phylogenetically informative characters within the Characidiinae. In the largest group of miniatures, reductive characters represent more than half of the character state transformations affecting supraspecific relationships among Elachocharax, Klausewitzia, Odontocharacidium and Microcharacidium . An analysis of patterns of character state distributions fails to reject the null hypothesis of character independence. A distinction is made between the concepts of character independence, defined as the origination of character states from different (non-simultaneous) evolutionary events, and character correlation, defined as the association of character states in terminal taxa. Character correlation is not a sufficient criterion to reject Hennig's auxiliary principle, according to which the "presence of apomorphous characters in different species is always reason for suspecting kinship, and their origin by convergence should not be assumed a priori". High values of character correlation are the expected result of congruent patterns of character distribution.     

The legacy of forest logging on organic matter inputs and storage in tropical streams

Riparian forests play an important role in stream ecosystems, as they support biodiversity, reduce water erosion, and provide litter that fuels aquatic biota. However, they are affected by great array of anthropogenic threats (e.g., fire, logging, and organic pollution), which alter species composition and their physical structure. Although forest recovery after disturbance such as logging can take decades, the legacy of forest clear-cut logging on key processes in tropical riparian ecosystems is mostly unknown. Here, we investigated how litter inputs (leaves, twigs, and reproductive parts) and storage, key processes for carbon and nutrient recycling and for forest and stream biota, are influenced by riparian vegetation undergoing succession (after 28 years from logging) through the comparison of reference and logged forest sites in the Cerrado biome. Litterfall was overall similar between forest types, but litterfall of twigs was twofold higher at logged than reference sites. Similarly, litter inputs from the bank to the stream (i.e., lateral inputs) and streambed storage were 50–60% higher at logged than reference sites. The higher litterfall observed in logged forests could be related to higher proportion of tree species that are characteristic of primary and secondary successional stages, including fast-growing and liana species, which often are more productive and common in anthropogenic areas. Our results showed that the legacy impact of clear-cut logging, even if residual woody vegetation is maintained in riparian buffers, can shift the type, quantity, and seasonality of litter subsidies to tropical streams. This knowledge should be considered within the context of management and conservation of communities and ecosystem processes in the forest-stream interfaces.     

αCT1 peptide sensitizes glioma cells to temozolomide in a glioblastoma organoid platform

Glioblastoma (GBM) is the most common form of brain cancer. Even with aggressive treatment, tumor recurrence is almost universal and patient prognosis is poor because many GBM cell subpopulations, especially the mesenchymal and glioma stem cell populations, are resistant to temozolomide (TMZ), the most commonly used chemotherapeutic in GBM. For this reason, there is an urgent need for the development of new therapies that can more effectively treat GBM. Several recent studies have indicated that high expression of connexin 43 (Cx43) in GBM is associated with poor patient outcomes. It has been hypothesized that inhibition of the Cx43 hemichannels could prevent TMZ efflux and sensitize otherwise resistance cells to the treatment. In this study, we use a three-dimensional organoid model of GBM to demonstrate that combinatorial treatment with TMZ and αCT1, a Cx43 mimetic peptide, significantly improves treatment efficacy in certain populations of GBM. Confocal imaging was used to visualize changes in Cx43 expression in response to combinatorial treatment. These results indicate that Cx43 inhibition should be pursued further as an improved treatment for GBM.