The effect of substrate abundance in the vertical stratification of bromeliad epiphytes in a tropical dry forest (Mexico)

Diversity of epiphytes is associated with niche partitioning, through vertical strata and host preferences. However, abundance of substrate offered by hosts differs between vertical strata, misleading if epiphytes prefer a stratum or are randomly distributed. In a tropical dry forest of San Andres de la Cal Morelos, central Mexico, we tested the null hypothesis, that epiphytes follow the abundance of the substrate, rather than showing preference for a particular vertical stratum, and tested whether microclimatic variables, seed germination and seedling survival match with observed epiphyte distribution. Our data show that epiphytes could be randomly distributed inside some host; but in some host species, certain structures presented either a deficit or an excess of all, atmospheric, or tank epiphytes. In the hosts Bursera copallifera and Bursera glabrifolia, distribution of epiphytes was biased towards the upper strata, with a deficit of epiphytes in the lower strata. In Conzattia multiflora, Sapium macrocarpum and Ipomoea pauciflora, epiphyte distribution was biased towards the lower strata. Vertical gradation of light, seed germination and seedling survival did not generally match with epiphyte distribution and did not support the notion that the microclimatic gradient governs the vertical distribution of epiphytes. Our data indicate that vertical distribution of epiphytes in such tropical dry forests is mainly driven by the distribution of the structures, which apparently influence dispersion of the seeds and by the lifespan of branches, which allow the concentration of epiphytes in the stratum that optimizes seed capture and the clonal growth of epiphytes.     

Breeding quinoa (Chenopodium quinoa Willd.): potential and perspectives

Quinoa (Chenopodium quinoa Willd.) originated in the Andean region of South America; this species is associated with exceptional grain nutritional quality and is highly valued for its ability to tolerate abiotic stresses. However, its introduction outside the Andes has yet to take off on a large scale. In the Andes, quinoa has until recently been marginally grown by small-scale Andean farmers, leading to minor interest in the crop from urban consumers and the industry. Quinoa breeding programs were not initiated until the 1960s in the Andes, and elsewhere from the 1970s onwards. New molecular tools available for the existing quinoa breeding programs, which are critically examined in this review, will enable us to tackle the limitations of allotetraploidy and genetic specificities. The recent progress, together with the declaration of “The International Year of the Quinoa” by the Food and Agriculture Organization of the United Nations, anticipates a bright future for this ancient species.     

Sublethal effects of chlorantraniliprole and thiamethoxam seed treatments when Lysiphlebus testaceipes feed on sunflower extrafloral nectar

The extrafloral nectar (EFN) of sunflower, Helianthus annuus L., is an important summer resource for many insects and represents a potential route of exposure to systemic insecticides applied as seed treatments to cultivated varieties. Among the many parasitoids that utilize sunflower EFN, Lysiphlebus testaceipes (Cresson) (Hymenoptera: Braconidae) is an important generalist parasitoid of cereal aphids in North America. This study evaluated the performance of adult wasps fed EFN of sunflower plants grown from seed treated with chlorantraniliprole and thiamethoxam. Consumption of EFN from treated sunflower seedings caused no lethal effects, but reduced the numbers of greenbug nymphs, Schizaphis graminum Rondani, attacked and parasitized when wasps foraged in Petri dish arenas. Whereas control females self-superparasitized every fourth host, those exposed to chlorantraniliprole did not. Offspring developmental time and adult emergence were unaffected by either treatment, but thiamethoxam greatly reduced the proportion of female offspring.     

Thiol redox biochemistry: insights from computer simulations

Thiol redox chemical reactions play a key role in a variety of physiological processes, mainly due to the presence of low-molecular-weight thiols and cysteine residues in proteins involved in catalysis and regulation. Specifically, the subtle sensitivity of thiol reactivity to the environment makes the use of simulation techniques extremely valuable for obtaining microscopic insights. In this work we review the application of classical and quantum–mechanical atomistic simulation tools to the investigation of selected relevant issues in thiol redox biochemistry, such as investigations on (1) the protonation state of cysteine in protein, (2) two-electron oxidation of thiols by hydroperoxides, chloramines, and hypochlorous acid, (3) mechanistic and kinetics aspects of the de novo formation of disulfide bonds and thiol−disulfide exchange, (4) formation of sulfenamides, (5) formation of nitrosothiols and transnitrosation reactions, and (6) one-electron oxidation pathways.     

Loop-Mediated Isothermal Amplification of Specific Endoglucanase Gene Sequence for Detection of the Bacterial Wilt Pathogen Ralstonia solanacearum

The increased globalization of crops production and processing industries also promotes the side-effects of more rapid and efficient spread of plant pathogens. To prevent the associated economic losses, and particularly those related to bacterial diseases where their management relies on removal of the infected material from production, simple, easy-to-perform, rapid and cost-effective tests are needed. Loop-mediated isothermal amplification (LAMP) assays that target 16S rRNA, fliC and egl genes were compared and evaluated as on-site applications. The assay with the best performance was that targeted to the egl gene, which shows high analytical specificity for diverse strains of the betaproteobacterium Ralstonia solanacearum, including its non-European and non-race 3 biovar 2 strains. The additional melting curve analysis provides confirmation of the test results. According to our extensive assessment, the egl LAMP assay requires minimum sample preparation (a few minutes of boiling) for the identification of pure cultures and ooze from symptomatic material, and it can also be used in a high-throughput format in the laboratory. This provides sensitive and reliable detection of R. solanacearum strains of different phylotypes.     

Joint Modeling and Registration of Cell Populations in Cohorts of High-Dimensional Flow Cytometric Data

In biomedical applications, an experimenter encounters different potential sources of variation in data such as individual samples, multiple experimental conditions, and multivariate responses of a panel of markers such as from a signaling network. In multiparametric cytometry, which is often used for analyzing patient samples, such issues are critical. While computational methods can identify cell populations in individual samples, without the ability to automatically match them across samples, it is difficult to compare and characterize the populations in typical experiments, such as those responding to various stimulations or distinctive of particular patients or time-points, especially when there are many samples. Joint Clustering and Matching (JCM) is a multi-level framework for simultaneous modeling and registration of populations across a cohort. JCM models every population with a robust multivariate probability distribution. Simultaneously, JCM fits a random-effects model to construct an overall batch template – used for registering populations across samples, and classifying new samples. By tackling systems-level variation, JCM supports practical biomedical applications involving large cohorts. Software for fitting the JCM models have been implemented in an R package EMMIX-JCM, available from http://www.maths.uq.edu.au/~gjm/mix_soft/EMMIX-JCM/.     

Use of Synthetic Genes for Cloning,Production and Functional Expression of the Bacteriocins Enterocin A and Bacteriocin E 50-52 by Pichia pastoris and Kluyveromyces lactis

The use of synthetic genes may constitute a successful approach for the heterologous production and functional expression of bacterial antimicrobial peptides (bacteriocins) by recombinant yeasts. In this work, synthetic genes with adapted codon usage designed from the mature amino acid sequence of the bacteriocin enterocin A (EntA), produced by Enterococcus faecium T136, and the mature bacteriocin E 50-52 (BacE50-52), produced by E. faecium NRRL B-32746, were synthesized. The synthetic entA and bacE50-52 were cloned into the protein expression vectors pPICZαA and pKLAC2 for transformation of derived vectors into Pichia pastoris X-33 and Kluyveromyces lactis GG799, respectively. The recombinant vectors were linearized and transformed into competent cells selecting for P. pastoris X-33EAS (entA), P. pastoris X-33BE50-52S (bacE50-52), K. lactis GG799EAS (entA), and K. lactis GG799BE50-52S (bacE50-52). P. pastoris X-33EAS and K. lactis GG799EAS, but not P. pastoris X-33BE50-52S and K. lactis GG799BE50-52S, showed antimicrobial activity in their supernatants. However, purification of the supernatants of the producer yeasts permitted recovery of the bacteriocins EntA and BacE50-52. Both purified bacteriocins were active against Gram-positive bacteria such as Listeria monocytogenes but not against Gram-negative bacteria, including Campylobacter jejuni.     

Bile acid supplementation improves established liver steatosis in obese mice independently of glucagon-like peptide-1 secretion

Bile acids or its derivatives may influence non-alcoholic fatty liver disease development through multiple mechanisms. Intestinal L-cells secrete glucagon-like peptide-1 (GLP-1) and can be activated by bile acids (BA) influencing insulin resistance and hepatic steatosis development and progression. The aim of the present study was to assess the effects of cholic acid (CA) or ursodeoxycholic acid (UDCA) administration on portal and systemic levels of GLP-1 in genetically obese mice with established hepatic steatosis. Eight-week-old ob/ob mice were fed CA or UDCA during 4 weeks. Systemic and portal GLP-1 levels were measured as well as glucose tolerance test, serum and biliary parameters, hepatic triglyceride content, liver histology, and hepatic gene expression of relevant genes related to bile secretion. Eight-week-old ob/ob mice exhibited marked obesity, hyperinsulinemia, and fasting hyperglycemia. Administration of both CA and UDCA was associated to decreased hepatic triglyceride content and complete reversion of histological steatosis. BA-fed animals did not exhibit significant differences in glucose tolerance. In addition, neither CA nor UDCA administration significantly influenced portal or systemic GLP-1 levels. CA and UDCA strongly ameliorated established fatty liver in ob/ob mice independently of the GLP-1 incretin pathway. Thus, the anti-steatotic action of these bile acids is likely related to direct hepatic effects.     

Intraguild predation: a widespread interaction related to species biology

Intraguild predation (IGP), defined as killing and eating among potential competitors, seems to be a ubiquitous interaction, differing from competition or predation. In the present study we assess the frequency of IGP among 763 potential intraguild prey and 599 potential intraguild predators. Our results indicate that IGP is common in nature, reaching frequencies between 58.4 and 86.7%. A null model suggests that IGP in different groups of predators and prey (i.e. carnivores, omnivores, herbivores, detritivores, or top and intermediate species) have different deviations from a chance expectation, indicating these attributes of species biology as main determinants of IGP persistence. We suggest that IGP satisfies two basic requirements to be considered as important to the trophic structuring of communities. First, its occurrence is not random, rather it is associated with well‐defined attributes of species biology, and secondly, it is a widespread interaction.