Nitrogen,water, and phosphorus uptake as functions of fine-root mass in greenhouse microcosms of Poa pratensis

Plant Ecology - Understanding resource uptake as a function of fine-root mass is important for both basic ecological theory and applied biogeochemical cycling models. We measured plant population...     

The behavioral immune system and social conservatism: a meta-analysis

The behavioral immune system (BIS) is a cluster of psychological mechanisms (e.g., disgust) that have evolved to promote disease-avoidance (Schaller M. (2006). Parasites, behavioral defenses, and the social psychological mechanisms through which cultures are evoked. Psychological Inquiry, 17, 96–101). Recent evidence suggests that the BIS may promote avoidance of outgroup members, an historical source of contamination, by evoking social conservatism (Terrizzi JA Jr, Shook NJ, & Ventis WL. (2010). Disgust: A predictor of social conservatism and prejudicial attitudes toward homosexuals. Personality and Individual Differences, 49, 587–592; Terrizzi J, Shook N, Ventis L. (2012). Religious conservatism: An evolutionarily evoked disease-avoidance strategy. Religion, Brain & Behavior, 2, 105–120.). That is, the BIS mechanisms may encourage the endorsement of socially conservative beliefs, which promote social exclusivity, tradition, and negativity toward outgroups. The current study provides a systematic review and meta-analysis of 24 studies to evaluate the hypothesis that the BIS is predictive of social conservatism. The results indicate that behavioral immune strength, as indicated by fear of contamination and disgust sensitivity, is positively related to social conservatism (i.e., right-wing authoritarianism, social dominance orientation, religious fundamentalism, ethnocentrism, collectivism, and political conservatism). These findings provide initial evidence that socially conservative values may function as evolutionarily evoked disease-avoidance strategies.     

Comparative assessment of the intracellular survival of the Burkholderia pseudomallei bopC mutant

Burkholderia pseudomallei, the causative agent of melioidosis, is a Gram-negative saprophytic bacterium capable of surviving within phagocytic cells. To assess the role of BopC (a type III secreted effector protein) in the pathogenesis of B. pseudomallei, a B. pseudomallei bopC mutant was used to infect J774A.1 macrophage-like cells. The bopC mutant showed significantly reduced intracellular survival in infected macrophages compared to wild-type B. pseudomallei. In addition, the bopC mutant displayed delayed escape from endocytic vesicles compared with the wild-type strain. This indicates that BopC is important, and at least in part, needed for intracellular survival of B. pseudomallei.     

Triacylglycerol Synthesis Enzymes Mediate Lipid Droplet Growth by Relocalizing from the ER to Lipid Droplets

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Highlights? Triacylglyceride (TG) synthesis is coupled with lipid droplet (LD) growth ? Two LD populations exist: growing LDs, containing TG enzymes, and small LDs ? Specific TG synthesis enzymes move from the ER to LDs through membrane bridges ? LD localization of TG enzymes mediates expansion of a subset of LDs     

Positive association between thrips and spider mites in seedling cotton

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A perforin‐like protein mediates disruption of the erythrocyte membrane during egress of Plasmodium berghei male gametocytes

Successful gametogenesis of the malaria parasite depends on egress of the gametocytes from the erythrocytes within which they developed. Egress entails rupture of both the parasitophorous vacuole membrane and the erythrocyte plasma membrane, and precedes the formation of the motile flagellated male gametes in a process called exflagellation. We show here that egress of the male gametocyte depends on the function of a perforin‐like protein, PPLP2. A mutant of Plasmodium berghei lacking PPLP2 displayed abnormal exflagellation; instead of each male gametocyte forming eight flagellated gametes, it produced gametocytes with only one, shared thicker flagellum. Using immunofluorescence and transmission electron microscopy analysis, and phenotype rescue with saponin or a pore‐forming toxin, we conclude that rupture of the erythrocyte membraneis blocked in the mutant. The parasitophorous vacuole membrane, on the other hand, is ruptured normally. Some mutant parasites are still able to develop in the mosquito, possibly because the vigorous motility of the flagellated gametes eventually leads to escape from the persisting erythrocyte membrane. This is the first example of a perforin‐like protein in Plasmodium parasites having a role in egress from the host cell and the first parasite protein shown to be specifically required for erythrocyte membrane disruption during egress.     

Comparative analysis of tandem repeats from hundreds of species reveals unique insights into centromere evolution

Background

Centromeres are essential for chromosome segregation, yet their DNA sequences evolve rapidly. In most animals and plants that have been studied, centromeres contain megabase-scale arrays of tandem repeats. Despite their importance, very little is known about the degree to which centromere tandem repeats share common properties between different species across different phyla. We used bioinformatic methods to identify high-copy tandem repeats from 282 species using publicly available genomic sequence and our own data.

Results

Our methods are compatible with all current sequencing technologies. Long Pacific Biosciences sequence reads allowed us to find tandem repeat monomers up to 1,419 bp. We assumed that the most abundant tandem repeat is the centromere DNA, which was true for most species whose centromeres have been previously characterized, suggesting this is a general property of genomes. High-copy centromere tandem repeats were found in almost all animal and plant genomes, but repeat monomers were highly variable in sequence composition and length. Furthermore, phylogenetic analysis of sequence homology showed little evidence of sequence conservation beyond approximately 50 million years of divergence. We find that despite an overall lack of sequence conservation, centromere tandem repeats from diverse species showed similar modes of evolution.

Conclusions

While centromere position in most eukaryotes is epigenetically determined, our results indicate that tandem repeats are highly prevalent at centromeres of both animal and plant genomes. This suggests a functional role for such repeats, perhaps in promoting concerted evolution of centromere DNA across chromosomes.     

Recruitment into stress granules prevents irreversible aggregation of FUS protein mislocalized to the cytoplasm

Fused in sarcoma (FUS) belongs to the group of RNA-binding proteins implicated as underlying factors in amyotrophic lateral sclerosis (ALS) and certain other neurodegenerative diseases. Multiple FUS gene mutations have been linked to hereditary forms, and aggregation of FUS protein is believed to play an important role in pathogenesis of these diseases. In cultured cells, FUS variants with disease-associated amino acid substitutions or short deletions affecting nuclear localization signal (NLS) and causing cytoplasmic mislocalization can be sequestered into stress granules (SGs). We demonstrated that disruption of motifs responsible for RNA recognition and binding not only prevents SG recruitment, but also dramatically increases the protein propensity to aggregate in the cell cytoplasm with formation of juxtanuclear structures displaying typical features of aggresomes. Functional RNA-binding domains from TAR DNA-binding protein of 43 kDa (TDP-43) fused to highly aggregation-prone C-terminally truncated FUS protein restored the ability to enter SGs and prevented aggregation of the chimeric protein. Truncated FUS was also able to trap endogenous FUS molecules in the cytoplasmic aggregates. Our data indicate that RNA binding and recruitment to SGs protect cytoplasmic FUS from aggregation, and loss of this protection may trigger its pathological aggregation in vivo.     

Findings from the Peutz-Jeghers Syndrome Registry of Uruguay

Background

Peutz-Jeghers syndrome (PJS) is characterized by intestinal polyposis, mucocutaneous pigmentation and an increased cancer risk, usually caused by mutations of the STK11 gene. This study collected epidemiological, clinical and genetic data from all Uruguayan PJS patients.

Methods

Clinical data were obtained from public and private medical centers and updated annually. Sequencing of the STK11 gene in one member of each family was performed.

Results and discussion

25 cases in 11 unrelated families were registered (15 males, 10 females). The average age of diagnosis and death was 18 and 41 years respectively. All patients had characteristic PJS pigmentation and gastrointestinal polyps. 72% required urgent surgery due to intestinal obstruction. 3 families had multiple cases of seizure disorder, representing 20% of cases. 28% developed cancer and two patients had more than one cancer. An STK11 mutation was found in 8 of the 9 families analyzed. A unique M136K missense mutation was noted in one family. Comparing annual live births and PJS birth records from 1970 to 2009 yielded an incidence of 1 in 155,000.

Conclusion

The Uruguayan Registry for Peutz-Jeghers patients showed a high chance of emergent surgery, epilepsy, cancer and shortened life expectancy. The M136K missense mutation is a newly reported STK 11 mutation.