Structural biology: Paper alert

A selection of interesting papers that were published in the two months before our press date in major journals most likely to report significant results in structural biology.     

Characterization of the biochemical,physiological, and medicinal properties of Streptomyces hygroscopicus ACTMS-9H isolated from the Amazon (Brazil)

Applied Microbiology and Biotechnology - Actinomycetes are known to produce numerous secondary bioactive metabolites of pharmaceutical interest. The purpose of this study was to isolate,...     

Biotic and abiotic changes along a cyclic succession driven by shrubs in semiarid steppes from Patagonia

Aim

We studied the legacy effects of shrubs during the downgrade phase of high–cover patches. Specifically, are woody species able to modify environmental attributes at patch level to such an extent as to alter the colonization once they have vacated their original position?

Methods

We monitored five environmental variables along an experimental four-stage downgrading gradient of high–cover patches during two years in cold- and warm-seasons, individual plant growth during three years, as well as the floristic composition of patches along the same gradient after 13 years.

Results

The downgrade of high–cover patches reduces the aboveground protection due to the increase in wind speed (400–500%) and evaporation rate (43–160%) associated with shrub death and senescence. In addition, high–cover patches increase the total soil nitrogen (400–600%) and reduce the infiltration rate (44–73%) on the top layer. Leaf length and flower culms of grass tussocks were lower in bare soil patches (7.5 cm and 3) compared to whatever degradation stage of high–cover patches (9–10 cm and 18–32). Floristic composition after 13 years reveals that grass species occupied the patch stages differentially, with a disjunctive pattern among species within the Poa and Pappostipa genus.

Conclusions

Legacy effects prompted by shrubs through changes in soil properties at the horizontal plane can conditioned the patch dynamics. The ability of different plant species to cope with the spatial heterogeneity at the horizontal plane should be included as a new criterion to define plant strategies from arid ecosystems according to the gap–phase dynamics and mosaic maintenance.

     

Environmental conditions modulate plasticity in the physiological responses of three plant species of the Neotropical savannah

Plasticity in plants could be changed due to abiotic factors, tending to increase fitness across environments. In the Neotropical savannah, a strong water deficit during the dry season is one of the main factors limiting the plasticity in physiological responses of plants. The present study aims to assess the plasticity in physiological responses and vegetative phenology of three plant species of the Neotropical savannah (Cerrado in Brazil) during the dry and the rainy seasons. The three species, Byrsonima verbascifolia, Roupala montana, and Solanum lycocarpum, occur in Serra do Cipó in the state of Minas Gerais, Brazil. The development and vegetative phenology of individuals of these three species were evaluated over the course of 1 year. In February 2012 (rainy season) and August 2012 (dry season), stomatal conductance (g _s), water potential (Ψ), photosynthetic quantum yield, and concentration of leaf photosynthetic pigments were measured. The relative distance among the physiological parameters of all individuals within each season was measured using the relative distance plasticity index. B. verbascifolia has pronounced senescence in July and lost leaves completely by the early September, while R. montana and S. lycocarpum have green leaves throughout the year. The three studied species had greater control of stomatal opening during the dry season. S. lycocarpum and R. montana had negative water potential values in the dry season and in the middle of the day in both seasons. In the dry season, the three species exhibited a decrease in F _v/F _m, with values between 0.7 and 0.75. The relative distance plasticity index varied from 0 to 1. R. montana demonstrated the greatest plasticity and S. lycocarpum had lower plasticity. Then, a seasonal effect on physiological response was observed in all three model-species, with lower values for leaf water potential and stomatal conductance, and increased photoinhibition, in the dry season. Ecophysiological traits, such as stomatal conductance and leaf water potential, exhibited the greatest plasticity. In addition, there was a seasonal effect on the plasticity in physiological responses of the three plants species of the Neotropical savannah. The results are contradicting the idea that water restriction in the dry season would reduce the plasticity in most species of the Neotropical savannah.     

The presence of the pilus locus is a clonal property among pneumococcal invasive isolates

Background  

Pili were recently recognized in Streptococcus pneumoniae and implicated in the virulence of this bacterium, which led to the proposal of using these antigens in a future pneumococcal vaccine. However, pili were found to be encoded by the rlrA islet that was not universally distributed in the species. We examined the distribution of the pilus islet, using the presence of the rlrA gene as a marker for the locus, among a collection of invasive isolates recovered in Portugal and analyzed its association with capsular serotypes, clusters defined by the pulsed-field gel electrophoretic profiles (PFGE) and multilocus sequence types.     

Survey of Alouatta caraya, the black-and-gold howler monkey, and Alouatta guariba clamitans, the brown howler monkey, in a contact zone, State of Rio Grande do Sul, Brazil: evidence for hybridization

Sympatry and natural hybridization between howler monkey taxa (Alouatta spp.) has only recently being confirmed in the wild. Surveys in areas of potential contact between the distribution of two taxa have shown that sympatry is rare, although more common than previously known. Here we report the results of a survey conducted in a contact zone between the only two sexually dichromatic howler monkey taxa, Alouatta caraya and A. guariba clamitans, in São Francisco de Assis, State of Rio Grande do Sul, Brazil. Our survey, covering an area of about 400 ha at the Cerro dos Negros (29°33′50″–29°35′10″S, 54°58′40″–54°59′50″W; ~100–279 m a.s.l.), was successful in locating seven black-and-gold and one brown howler monkey social groups living syntopically. Black-and-gold group size ranged from 5 to 15 individuals, whereas the brown group was composed of 7 individuals. The pelage color of three adult males belonging to different black-and-gold groups and another adult male belonging to the brown howler group presented a mosaic of red or rufous and black. These adult males and an adult female living in another black-and-gold group are putative hybrids. Therefore, it appears that pre-zygotic reproductive isolation has not evolved, at least not completely, between these howler monkey species, corroborating previous reports for these and other Alouatta taxa. Future genetic studies need to confirm the occurrence of hybridization in this contact zone, and to determine the viability and fertility of hybrids and their possible offspring. In addition, there is no evidence supporting the existence of significant segregation in habitat and resource utilization by black-and-gold and brown howler monkeys.     

Source-sink regulation of cotyledonary reserve mobilization during cashew (Anacardium occidentale) seedling establishment under NaCl salinity

Seedling establishment is a critical process to crop productivity, especially under saline conditions. This work was carried out to investigate the hypothesis that reserve mobilization is coordinated with salt-induced inhibition of seedling growth due to changes in source-sink relations. To test this hypothesis, cashew nuts (Anacardium occidentale) were sown in vermiculite irrigated daily with distilled water (control) or 50mM NaCl and they were evaluated at discrete developmental stages from the seed germination until the whole seedling establishment. The salt treatment coordinately delayed the seedling growth and the cotyledonary reserve mobilization. However, these effects were more pronounced at late seedling establishment than in earlier stages. The storage protein mobilization was affected by salt stress before the lipid and starch breakdown. The globulin fraction represented the most important storage proteins of cashew cotyledons, and its mobilization was markedly delayed by NaCl along the seedling establishment. Free amino acids were mostly retained in the cotyledons of salt-treated seedlings when the mobilization of storage proteins, lipids and starch was strongly delayed. Proline was not considerably accumulated in the cotyledons of cashew seedlings as a response to NaCl salinity. According to these results it is noteworthy that the salt-induced inhibition of seedling growth is narrowly coordinated with the delay of reserve mobilization and the accumulation of hydrolysis products in cotyledons. Also, it was evidenced that free amino acids, especially those related to nitrogen transport, are potential signals involved in the regulation of storage protein hydrolysis during cashew seedling establishment under NaCl salinity.     

Group size and composition of black-and-gold howler monkeys (<Emphasis Type="Italic">Alouatta caraya</Emphasis>) on the Upper Paraná River,Southern Brazil

In social mammals, group size, sex and age-class composition are important parameters that are required to understand population dynamics and determine conservation strategies. These parameters are known only poorly for the black-and-gold howler monkey (Alouatta caraya). Here, we studied groups of A. caraya on islands and adjacent banks of the Upper Paraná River of southern Brazil, to examine variability in group size and composition. This location is important for this species because of the high density of howlers. Group size was large, varying from 6 to 18 individuals (average = 11.5, standard deviation = 3.3, n = 13). Groups were multi-male, and adult females outnumbered adult males. On average, groups had the following ratios: 1 adult male: 0.5 subadult male: 1.9 adult females: 0.9 juveniles: 0.5 infants. The ratio of 0.2 infant: 1 adult female is less than that in other species, but typical of other studies of the black-and-gold howlers. Here, we discuss environmental and social pressures that may impose structure on large groups of howlers in terms of strategies for living in high densities. We also compare these data with those of the area of sympatry shared between A. caraya and A. clamitans, and suggest that competition may occur between the two species and that reduced fitness may be a consequence of mixed groups. Contribution number 1,746 of the Departamento de Zoologia of Universidade Federal do Paraná (UFPR).     

Aluminum accumulation and its relationship with mineral plant nutrients in 12 pteridophytes from Venezuela

The purpose of this study was to investigate the aluminum (Al) concentration in Lycopodium clavatum, Dicranopteris flexuosa, Sticherus nudus, Anemia villosa, Cyathea gibbosa, Pteridium arachnoideum, Pteris vittata, Thelypteris dentata, Blechnum occidentale, Elaphoglossum sporadolepis, Nephrolepis cordifolia and Polypodium pseudoaureum, species from 11 families with different phylogenetic position, found on soils with a high concentration of Al (up to 13 g kg^?1 dry mass (DM)). When Al concentration and mineral nutrients in aerial organs were considered, pteridophytes were classified into three groups: group one included pteridophytes with Al concentrations over 1000 mg kg^?1 DM in their aerial organs, a ratio between Al and essential plant nutrients such as Ca, Mg and P higher than one and a K/Al ratio between 0.68 and 2.56 mol mol^?1. In group 1 was the well known Al-accumulator L. clavatum (Lycophyte) as well as the Neotropical ferns D. flexuosa, S. nudus (both basal leptosporangiate ferns), and C. gibbosa (core leptosporangiate tree fern). Group 2, ferns which accumulate Al over 1000 mg kg^?1 DM in their fronds, and had an Al/Ca and Al/Mg ratio <1. Species in this group included E. sporadolepis and N. cordifolia (derived polypod ferns). Group 3, ferns classified as Al-excluders, showing Al concentration <782 mg kg^?1 DM in the fronds, had Al/Ca and Al/Mg ratios <1, Al/P ratio ≤1 and a K/Al ratio between 18.10 and 80.36 mol mol^?1. In group 3, were A. villosa (basal leptosporangiate fern) and the derived polypod ferns P. arachnoideum, P. vittata, T. dentata, B. occidentale and P. pseudoaureum. The translocation factor of Al from subterranean to aerial organs was up to 4 in S. nudus, and subterranean organs from E. sporadolepis showed the highest concentration of Al (12 g kg^?1 DM). We coincide with early literature in that other criteria in addition to the Al concentration should be considered to define the Al accumulation, such as its relationship with macronutrients. For example, we propose the inclusion of K/Al ratio. We conclude that out of six Al-excluders five belonged to the derived polypods while two species from Polypodiales showed high Al concentrations. We reconfirm accumulation of Al in L. clavatum and C. gibbosa and discover two new Al-accumulating species in the more ancient ferns: S. nudus and D. flexuosa.