Distributional patterns of Neotropical seasonally dry forest birds: a biogeographical regionalization

Neotropical seasonally dry forests (NSDFs) are widely distributed and possess high levels of species richness and endemism; however, their biogeography remains only partially understood. Using species distribution modelling and parsimony analysis of endemicity, we analysed the distributional patterns of the NSDF avifauna in order to identify their areas of endemism and provide a better understanding of the historical relationships among those areas. The strict consensus trees revealed 17 areas of endemism for NSDFs, which involve four large regions: Baja California, Caribbean–Antilles islands, Mesoamerica and South America. These well-resolved clades are circumscribed by geographical and ecological barriers associated with the Gulf of California, the leading edge of the Caribbean plate, the Tehuantepec Isthmus, the Polochic–Motagua fault, the Nicaragua Depression, the Chocó forest, the Amazon basin and the Andean Cordillera. Relationships among groups of NSDFs found here suggest that evolution of their avifauna involved a mixture of vicariance and dispersal events. Our results support the idea of independent diversification patterns and biogeographical processes in each region, including those previously associated with the Pleistocene Arc Hypothesis for NSDFs of south-eastern South America. This study provides a biogeographical framework to open new lines of research related to the biotic diversification of NSDFs.     

Scaling up calcification,respiration, and photosynthesis rates of six prominent coral taxa

Coral reefs provide a range of important services to humanity, which are underpinned by community‐level ecological processes such as coral calcification. Estimating these processes relies on our knowledge of individual physiological rates and species‐specific abundances in the field. For colonial animals such as reef‐building corals, abundance is frequently expressed as the relative surface cover of coral colonies, a metric that does not account for demographic parameters such as coral size. This may be problematic because many physiological rates are directly related to organism size, and failure to account for linear scaling patterns may skew estimates of ecosystem functioning. In the present study, we characterize the scaling of three physiological rates — calcification, respiration, and photosynthesis — considering the colony size for six prominent, reef‐building coral taxa in Mo''orea, French Polynesia. After a seven‐day acclimation period in the laboratory, we quantified coral physiological rates for three hours during daylight (i.e., calcification and gross photosynthesis) and one hour during night light conditions (i.e., dark respiration). Our results indicate that area‐specific calcification rates are higher for smaller colonies across all taxa. However, photosynthesis and respiration rates remain constant over the colony‐size gradient. Furthermore, we revealed a correlation between the demographic dynamics of coral genera and the ratio between net primary production and calcification rates. Therefore, intraspecific scaling of reef‐building coral physiology not only improves our understanding of community‐level coral reef functioning but it may also explain species‐specific responses to disturbances.     

Diversity of bacteriocins in the microbiome of the Tucuruí Hydroelectric Power Plant water reservoir and three-dimensional structure prediction of a zoocin

Bacteriocins are antimicrobial peptides expressed by bacteria through ribosomal activity. In this study, we analyzed the diversity of bacteriocin-like genes in the Tucuruí-HPP using a whole-metagenome shotgun sequencing approach. Three layers of the water column were analyzed (photic, aphotic and sediment). Detection of bacteriocin-like genes was performed with blastx using the BAGEL4 database as subject sequences. In order to calculate the abundance of bacteriocin-like genes we also determined the number of 16S rRNA genes using blastn. Taxonomic analysis was performed using RAST server and the metagenome was assembled using IDBA-UD in order to recover the full sequence of a zoocin which had its three-dimensional structure determined. The photic zone presented the highest number of reads affiliated to bacteriocins. The most abundant bacteriocins were sonorensin, Klebicin D , pyocin and colicin. The zoocin model was composed of eight anti-parallel β-sheets and two α-helices with a Zn²⁺ ion in the active site. This model was considerably stable during 10 ns of molecular dynamics simulation. We observed a high diversity of bacteriocins in the Tucuruí-HPP, demonstrating that the environment is an inexhaustible source for prospecting these molecules. Finally, the zoocin model can be used for further studies of substrate binding and molecular mechanisms involving peptidoglycan degradation.     

Purification and characteristics of cytosolic chitinase from Piromyces communis OTS1

Abstract A chitinase was purified from the cytosolic fraction of the anaerobic rumen fungus Piromyces communis OTS1 by affinity chromatography using regenerated chitin, gel filtration and chromatofocusing. The chitinase was most active at pH 6.2 and at 60 °C in a 20-min assay. The molecular mass of the purified protein was estimated by SDS-PAGE to be 42 kDa and its pI was 4.9. The enzyme activity, which was of the 'endo' type, was inhibited by A⁺, Hg²⁺ and allosamidin. N -Acetyl- β -glucosaminidase and 'exo' type chitinase activity were absent from the purified preparation.     

Effect of the presence and location of corpus luteum on competence of bovine cumulus-oocyte complexes

This study aimed to determine the effect of presence of the corpus luteum (CL) and its influence on cumulus–oocyte complexes (COCs) obtained from the ipsilateral or contralateral ovary in bovine on the recovery and capacity of the oocytes to sustain mono-spermic fertilization, undergo preimplantation development, and develop to the blastocyst stage. Ovaries were collected at a local slaughterhouse and kept in pairs corresponding to the same animal. In the first experiment the variables evaluated were compared between cows with (CCL⁺) and without (CCL^-) CL, and for the second experiment, comparisons were made between ovaries with an ipsilateral (CL⁺), contralateral (CL⁻), and no (NCL). The recovery rate of COCs was higher in ovaries from CCL⁻ cows, and a higher proportion of grade 1 COCs were recovered from this group. A higher proportion of metaphase I oocytes at 7 h of maturation, and a higher rate of cleavage were observed in the CCL⁺ group; however, a higher proportion of embryos were obtained from the CCL⁻ group. Besides, COCs from the CL⁺ group had a lower proportion of grades 1 and 2 morphological qualities, lower rate of metaphase II oocytes at 22 h of maturation, and lower rate of formation of two pronuclei, whereas a higher proportion of unfertilized oocytes after in vitro fertilization. On the other hand, the COCs from the CL⁻ group displayed a lower proportion of oocytes with more than two pronuclei, higher cleavage rate, and higher final blastocyst production were obtained when compared to CL+. Thus, the effects of CL on the competence of bovine COCs are different depending on the anatomical proximity of their location in the animal, negatively affecting the quality of COCs located in the same ovary, but not having negative effects on the competence of COCs in the ovaries contralateral to their location.     

Signaling by the integrated stress response kinase PKR is fine-tuned by dynamic clustering

The double-stranded RNA sensor kinase PKR is one of four integrated stress response (ISR) sensor kinases that phosphorylate the α subunit of eukaryotic initiation factor 2 (eIF2α) in response to stress. The current model of PKR activation considers the formation of back-to-back PKR dimers as a prerequisite for signal propagation. Here we show that PKR signaling involves the assembly of dynamic PKR clusters. PKR clustering is driven by ligand binding to PKR’s sensor domain and by front-to-front interfaces between PKR’s kinase domains. PKR clusters are discrete, heterogeneous, autonomous coalescences that share some protein components with processing bodies. Strikingly, eIF2α is not recruited to PKR clusters, and PKR cluster disruption enhances eIF2α phosphorylation. Together, these results support a model in which PKR clustering may limit encounters between PKR and eIF2α to buffer downstream signaling and prevent the ISR from misfiring.