Plant stress granules and mRNA processing bodies are distinct from heat stress granules

Similar to the situation in mammalian cells and yeast, messenger ribonucleo protein (mRNP) homeostasis in plant cells depends on rapid transitions between three functional states, i.e. translated mRNPs in polysomes, stored mRNPs and mRNPs under degradation. Studies in mammalian cells showed that whenever the dynamic exchange of the components between these states is disrupted, stalled mRNPs accumulate in cytoplasmic aggregates, such as stress granules (SGs) or processing bodies (PBs). We identified PBs and SGs in plant cells by detection of DCP1, DCP2 and XRN4, as marker proteins for the 5'-->3' mRNA degradation pathway, and eIF4E, as well as the RNA binding proteins RBP47 and UBP1, as marker proteins for stored mRNPs in SGs. Cycloheximide-inhibited translation, stress treatments and mutants defective in mRNP homeostasis were used to study the dynamic transitions of mRNPs between SGs and PBs. SGs and PBs can be clearly discriminated from the previously described heat stress granules (HSGs), which evidently do not contain mRNPs. Thus, the role of HSGs as putative mRNP storage sites must be revised.     

Transient receptor potential channel A1 is directly gated by calcium ions

Members of the superfamily of transient receptor potential (TRP) channels are proposed to play important roles in sensory physiology. As an excitatory ion channel TRPA1 is robustly activated by pungent irritants in mustard and garlic and is suggested to mediate the inflammatory actions of environmental irritants and proalgesic agents. Here, we demonstrate that, in addition to pungent natural compounds, Ca(2+) directly gates heterologously expressed TRPA1 in whole-cell and excised-patch recordings with an apparent EC(50) of 905 nm. Pharmacological experiments and site-directed mutagenesis indicate that the N-terminal EF-hand calcium-binding domain of the channel is involved in Ca(2+)-dependent activation. Furthermore, we determine Ca(2+) as prerequisite for icilin activity on TRPA1.     

Evolution of a Saccharomyces cerevisiae metabolic pathway in Escherichia coli

The Saccharomyces cerevisiae glycerol pathway (GPD1 and GPP2) was evolved in vivo in Escherichia coli. The central metabolism of E. coli was engineered to link glucose consumption and glycerol production. The engineered strain was evolved in a chemostat culture and a high glycerol producer was rapidly obtained. The evolution of the strain was associated to a deletion between GPD1 and GPP2, resulting in the production of a fusion protein with both glycerol-3-P dehydrogenase and glycerol-3-P phosphatase activities. The higher efficiency of the fusion protein was due to partial glycerol-3-P channeling between the two active sites. The evolved strain produces glycerol from glucose at high yield, concentration and productivity.     

Association of secreted frizzled-related protein 4 (SFRP4) with type 2 diabetes in patients with stable coronary artery disease

Background

The interplay between the novel adipokine retinol-binding protein-4 (RBP4) and coronary artery disease (CAD) is still obscure. We investigated the relationship between RBP4 levels and the presence and severity of angiographically proven CAD and determined its possible role in acute myocardial infarction (AMI).

Methods

305 individuals with angiographically proven CAD (CAD-patients), were classified into 2 subgroups: 1) acute myocardial infarction (AMI, n = 141), and 2) stable angina (SA, n = 164). Ninety-one age- and sex-matched individuals without CAD, but with at least 2 classical cardiovascular risk factors, served as controls (non-CAD group). RBP4 serum levels were measured at hospital admission and were analyzed in relation to the coronary severity stenosis, assessed by the Gensini-score and the number of coronary narrowed vessels. Other clinical parameters, including insulin levels, HOMA-IR, hsCRP, glycaemic and lipid profile, and left-ventricular ejection fraction were also assessed.

Results

Serum RBP4 levels were significantly elevated in patients with CAD compared to non-CAD patients (39.29  ± 11.72 mg/L vs. 24.83  ± 11.27 mg/L, p < 0.001). We did not observe a significant difference in RBP4 levels between AMI and SA subgroups (p = 0.734). Logistic regression analysis revealed an independent association of CAD presence with serum RBP4 (β = 0.163, p = 0.006), and hsCRP (β = 0.122, p = 0.022) levels, in the whole study group. Among variables, hsCRP (β = 0.220), HDL (β = β0.150), and RBP4 (β = 0.297), correlated in both univariate and multivariate analysis with CAD severity (R² = 0.422, p < 0.001). Similarly, RBP4 concentrations increased with the number of coronary narrowed vessels (p < 0.05).

Conclusion

Patients with CAD, both SA and AMI, showed elevated RBP4 serum levels. Notably, increased RBP4 concentration seemed to independently correlate with CAD severity, but no with AMI.

Trial registration

The ClinicalTrials.gov Identifier is: NCT00636766

     

Folding up and Moving on—Nascent Protein Folding on the Ribosome

All cellular proteins are synthesized by the ribosome, an intricate molecular machine that translates the information of protein coding genes into the amino acid alphabet. The linear polypeptides synthesized by the ribosome must generally fold into specific three-dimensional structures to become biologically active. Folding has long been recognized to begin before synthesis is complete. Recently, biochemical and biophysical studies have shed light onto how the ribosome shapes the folding pathways of nascent proteins. Here, we discuss recent progress that is beginning to define the role of the ribosome in the folding of newly synthesized polypeptides.     

Establishing zebrafish as a novel exercise model: swimming economy, swimming-enhanced growth and muscle growth marker gene expression

Background

Zebrafish has been largely accepted as a vertebrate multidisciplinary model but its usefulness as a model for exercise physiology has been hampered by the scarce knowledge on its swimming economy, optimal swimming speeds and cost of transport. Therefore, we have performed individual and group-wise swimming experiments to quantify swimming economy and to demonstrate the exercise effects on growth in adult zebrafish.

Methodology/Principal Findings

Individual zebrafish (n = 10) were able to swim at a critical swimming speed (U_crit) of 0.548±0.007 m s⁻¹ or 18.0 standard body lengths (BL) s⁻¹. The optimal swimming speed (U_opt) at which energetic efficiency is highest was 0.396±0.019 m s⁻¹ (13.0 BL s⁻¹) corresponding to 72.26±0.29% of U_crit. The cost of transport at optimal swimming speed (COT_opt) was 25.23±4.03 µmol g⁻¹ m⁻¹. A group-wise experiment was conducted with zebrafish (n = 83) swimming at U_opt for 6 h day⁻¹ for 5 days week⁻¹ for 4 weeks vs. zebrafish (n = 84) that rested during this period. Swimming zebrafish increased their total body length by 5.6% and body weight by 41.1% as compared to resting fish. For the first time, a highly significant exercise-induced growth is demonstrated in adult zebrafish. Expression analysis of a set of muscle growth marker genes revealed clear regulatory roles in relation to swimming-enhanced growth for genes such as growth hormone receptor b (ghrb), insulin-like growth factor 1 receptor a (igf1ra), troponin C (stnnc), slow myosin heavy chain 1 (smyhc1), troponin I2 (tnni2), myosin heavy polypeptide 2 (myhz2) and myostatin (mstnb).

Conclusions/Significance

From the results of our study we can conclude that zebrafish can be used as an exercise model for enhanced growth, with implications in basic, biomedical and applied sciences, such as aquaculture.     

Linking micromorphism,brooding, and hermaphroditism in brachiopods: Insights from Caribbean Argyrotheca (Brachiopoda)

In extant brachiopods, parental brooding of the larvae occurs exclusively within Rhynchonelliformea. Methods of larval protection range from simple retention of the larvae within the mantle cavity, to sophisticated brood care within highly specialized brood pouches found in Argyrotheca and Joania (Terebratulida, Megathyridoidea), Gwynia (Terebratulida, Gwynioidea), and all Thecideoidea (Thecideida). Previous studies on the reproductive biology of Argyrotheca yielded contrasting results on the epithelial origin of the brood pouches in this genus. Here, representatives of different species of Argyrotheca from the Belize Barrier Reef were examined using histological section series. Brood pouches of four species, A. cf. schrammi and Argyrotheca sp. 1–3, are of the same basic structure, formed by invaginations of the anterior body wall and connected to the visceral cavity via the metanephridia. The same four species are simultaneously hermaphroditic, suggesting that fertilization is achieved, at least partly, through selfing. One species, Argyrotheca rubrocostata, differs significantly from all others as it has no brood pouch and gonochoric gonads. Thus, the presence of brood pouches and simultaneous hermaphroditism are concluded to be correlated within Megathyridoidea and proposed to be homologous traits of Joania and several but not all species of Argyrotheca, questioning the monophyletic status of both genera. In contrast to the brood pouches of Thecideoidea, lophophoral epithelium is not involved in the formation of the pouches of Argyrotheca and Joania. Therefore, megathyridoid and thecideoid brood pouches are not homologous but evolved independently within rhynchonelliform brachiopods. All brachiopods with brood pouches share a micromorphic form and a short life span, limiting the space and time available for gamete and larval development. We suggest that the brood pouches and the hermaphroditic gonads of Argyrotheca spp. and Joania compensate these limitations by minimizing the loss of gametes and larvae, and by maximizing the chances of successful fertilization. J. Morphol., 2013. © 2013 Wiley Periodicals, Inc.     

Ecologically based definition of seasons clarifies predator–prey interactions

Species interactions within food webs are driven by multiple constraints, including those imposed by seasonal changes in the environment. Ecologically sound definitions of seasons may therefore be a prerequisite for clarifying predator prey interactions. Most studies define biological seasons based on fixed schedules or on temporal changes in a single movement measurement. We used a novel clustering approach based on homogeneous space‐use patterns of GPS‐collared animals to reveal 7 biological seasons for caribou Rangifer tarandus caribou, and 5 for both moose Alces alces and grey wolves Canis lupus interacting in a boreal ecosystem. Subsequent evaluation of niche overlap showed that, as predicted, wolves had a stronger spatio‐temporal connection with moose, its main prey, than with caribou. Movement constraints and limiting resource distributions similarly affected all species in some instances, but also caused temporal changes in the extent of niche overlap between wolves and its two prey. The risk that caribou faced was not only linked to the niche overlap with wolves, but also to the extent of wolf‐moose niche overlap during the same period. Food‐web properties emerged from the analysis, with temporal changes in relative niche overlap reflecting the strength of trophic interactions during the year. Our study demonstrates how the study of trophic interactions can benefit from comprehensive definitions of biological seasons.