Microbiome-related aspects of locust density-dependent phase transition

Locust plagues are a notorious, ancient phenomenon. These swarming pests tend to aggregate and perform long migrations, decimating cultivated fields along their path. When population density is low, however, the locusts will express a cryptic, solitary, non-aggregating phenotype that is not considered a pest. Although the transition from the solitary to the gregarious phase has been well studied, associated shifts in the locust's microbiome have yet to be addressed. Here, using 16S rRNA amplicon sequencing, we compared the bacterial composition of solitary desert locusts before and after a phase transition. Our findings revealed that the microbiome is altered during the phase transition, and that a major aspect of this change is the acquisition of Weissella (Firmicutes). Our findings led us to hypothesize that the locust microbiome plays a role in inducing aggregation behaviour, contributing to the formation and maintenance of a swarm. Employing a mathematical model, we demonstrate the potential evolutionary advantage of inducing aggregation under different conditions; specifically, when the aggregation-inducing microbe exhibits a relatively high horizontal transmission rate. This is the first report of a previously unknown and important aspect of locust phase transition, demonstrating that the phase shift includes a shift in the gut and integument bacterial composition.     

Gene expression and the concept of the phenotype

While the definition of the 'genotype' has undergone dramatic changes in the transition from classical to molecular genetics, the definition of the 'phenotype' has remained for a long time within the classical framework. In addition, while the notion of the genotype has received significant attention from philosophers of biology, the notion of the phenotype has not. Recent developments in the technology of measuring gene-expression levels have made it possible to conceive of phenotypic traits in terms of levels of gene expression. We demonstrate that not only has this become possible but it has also become an actual practice. This suggests a significant change in our conception of the phenotype: as in the case of the 'genotype', phenotypes can now be conceived in quantitative and measurable terms on a comprehensive molecular level. We discuss in what sense gene expression profiles can be regarded as phenotypic traits and whether these traits are better described as a novel concept of phenotype or as an extension of the classical concept. We argue for an extension of the classical concept and call for an examination of the type of extension involved.     

Hyperchlorhidrosis caused by homozygous mutation in CA12, encoding carbonic anhydrase XII

Excessive chloride secretion in sweat (hyperchlorhidrosis), leading to a positive sweat test, is most commonly indicative of cystic fibrosis yet is found also in conjunction with various metabolic, endocrine, and dermatological disorders. There is conflicting evidence regarding the existence of autosomal-recessive hyperchlorhidrosis. We now describe a consanguineous Israeli Bedouin kindred with autosomal-recessive hyperchlohidrosis whose sole symptoms are visible salt precipitates after sweating, a preponderance to hyponatremic dehydration, and poor feeding and slow weight gain at infancy. Through genome-wide linkage analysis, we demonstrate that the phenotype is due to a homozygous mutation in CA12, encoding carbonic anhydrase XII. The mutant (c.427G>A [p.Glu143Lys]) protein showed 71% activity of the wild-type enzyme for catalyzing the CO₂ hydration to bicarbonate and H⁺, and it bound the clinically used sulfonamide inhibitor acetazolamide with high affinity (K_I of 10 nM). Unlike the wild-type enzyme, which is not inhibited by chloride, bromide, or iodide (K_Is of 73–215 mM), the mutant is inhibited in the submicromolar range by these anions (K_Is of 0.37–0.73 mM).     

Light-Induced Changes within Photosystem II Protects Microcoleus sp. in Biological Desert Sand Crusts against Excess Light

The filamentous cyanobacterium Microcoleus vaginatus, a major primary producer in desert biological sand crusts, is exposed to frequent hydration (by early morning dew) followed by desiccation during potentially damaging excess light conditions. Nevertheless, its photosynthetic machinery is hardly affected by high light, unlike “model” organisms whereby light-induced oxidative stress leads to photoinactivation of the oxygen-evolving photosystem II (PSII). Field experiments showed a dramatic decline in the fluorescence yield with rising light intensity in both drying and artificially maintained wet plots. Laboratory experiments showed that, contrary to “model” organisms, photosynthesis persists in Microcoleus sp. even at light intensities 2–3 times higher than required to saturate oxygen evolution. This is despite an extensive loss (85–90%) of variable fluorescence and thermoluminescence, representing radiative PSII charge recombination that promotes the generation of damaging singlet oxygen. Light induced loss of variable fluorescence is not inhibited by the electron transfer inhibitors 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), 2,5-dibromo-3-methyl-6-isopropylbenzoquinone (DBMIB), nor the uncoupler carbonyl cyanide-p-trifluoromethoxyphenylhydrazone (FCCP), thus indicating that reduction of plastoquinone or O₂, or lumen acidification essential for non-photochemical quenching (NPQ) are not involved. The rate of Q_A ⁻ re-oxidation in the presence of DCMU is enhanced with time and intensity of illumination. The difference in temperatures required for maximal thermoluminescence emissions from S₂/Q_A ⁻ (Q band, 22°C) and S_2,3/Q_B ⁻ (B band, 25°C) charge recombinations is considerably smaller in Microcoleus as compared to “model” photosynthetic organisms, thus indicating a significant alteration of the S₂/Q_A ⁻ redox potential. We propose that enhancement of non-radiative charge recombination with rising light intensity may reduce harmful radiative recombination events thereby lowering ¹O₂ generation and oxidative photodamage under excess illumination. This effective photo-protective mechanism was apparently lost during the evolution from the ancestor cyanobacteria to the higher plant chloroplast.     

A short mitochondrial form of p19ARF induces autophagy and caspase-independent cell death

The tumor suppressor functions of p19(ARF) have been attributed to its ability to induce cell cycle arrest or apoptosis by activating p53 and regulating ribosome biogenesis. Here we describe another cellular function of p19(ARF), involving a short isoform (smARF, short mitochondrial ARF) that localizes to a Proteinase K-resistant compartment of the mitochondria. smARF is a product of internal initiation of translation at Met45, which lacks the nucleolar functional domains. The human p14(ARF) mRNA likewise produces a shorter isoform. smARF is maintained at low levels via proteasome-mediated degradation, but it increases in response to viral and cellular oncogenes. Ectopic expression of smARF reduces mitochondrial membrane potential (DeltaPsim) without causing cytochrome c release or caspase activation. The dissipation of DeltaPsim does not depend on p53 or Bcl-2 family members. smARF induces massive autophagy and caspase-independent cell death that can be partially rescued by knocking down ATG5 or Beclin-1, suggesting a different prodeath function for this short isoform.     

Organization of chlorophyll-protein complexes of Photosystem I in Chlamydomonas reinhardii

The polypeptide pattern, chlorophyll-protein complexes, fluorescence emission spectra and light intensity required for saturation of electron flow via Photosystem (PS) II and PS I in a pale-green photoautotrophic mutant, y-lp, were compared to those of the parent strain, Chlamydomonas reinhardii y-1 cells. The mutant exhibits a 686 nm fluorescence yield at 25°C and 77 K 2–6-fold higher than that of the parent strain cells, and is deficient in thylakoid polypeptides 14, 17.2, 18 and 22 according to the nomenclature of Chua (Chua, N.-H. (1980) Methods Enzymol. 60C, 434–446). All chlorophyll-protein complexes ascribed to PS II and the CP I complex were present in both type of cells. However, a chlorophyll-protein complex CP Ia containing — in the parent strain — the 66–68 kDa polypeptides of CP I and the four above-mentioned polypeptides, was absent in the mutant. It was previously reported that a chlorophyll-protein complex, CP O, obtained from C. reinhardii contains five polypeptides, namely, 14, 15, 17.2, 18 and 22 (Wollman, F.A. and Bennoun, P. (1982) Biochim. Biophys. Acta 680, 352–360). A CP O-like complex was present also in the mutant y-lp cells but it contains only one polypeptide, 15. Energy transfer from PS II to PS I was not impaired in the mutant, although a 4-fold higher light intensity was required for the saturation of PS I electron flow in the y-lp cells as compared with the parent strain. No difference was found in the light saturation curves for PS II activity between the mutant and parent strain cells. Based on these and additional data (Gershoni, J.M., Shochat, S., Malkin, S. and Ohad, I. (1982) Plant Physiol. 70, 637–644), it is concluded that the chlorophyll-protein complexes of PS I in Chlamydomonas comprise a reaction center-core antenna complex containing the 66–68 kDa polypeptides (CP I), a connecting antenna consisting of four polypeptides (14, 17.2, 18 and 22), and a light-harvesting antenna containing one polypeptide, 15. These appear to be organized as a complex, CP Ia. The interconnecting antenna is deficient in the y-lp mutant and thus the CP Ia complex is unstable and energy is not transferred from CP O to CP I. The effective cross-section of PS I antenna is thus reduced and a high fluorescence is emitted at 686 nm.     

Preparation of Antibodies against Specific Chloroplast Membrane Polypeptides Associated with the Formation of Photosystems I and II in Chlamydomonas reinhardi y-1

The major Chlamydomonas reinhardi y-1 chloroplast membrane polypeptides-I + II, IV, V(a + b)-have been isolated by use of preparative sodium dodecyl sulfate-gel electrophoresis.     

Beneficial effect of fluorocarbon emulsion media on the function of neuromuscular preparations in vitro

The effects of liquid fluorocarbons as bathing media were determined by use of in vitro neuromuscular preparations. Rat hemidiaphragms were bathed in either oxygenated fluorocarbon (FC) emulsion or standard oxygenated Krebs solution. Contractile force in response to simple supramaximal nerve stimuli as well as to high frequency stimulation was greater, while twitch:tetanus ratio was smaller in FC emulsion. With such medium, post-tetanic potentiation of contraction was also more consistently observed. Indirectly stimulated diaphragms survived longer in FC emulsion. After cessation of oxygenation, oxygen tension (ρO(2)) of the medium declined more rapidly with Krebs than with FC emulsion; ρO(2) directly correlated with force of contraction. Similarly, in the chick biventer cervicis preparation, FC emulsion enhanced nerve-stimulated force of contraction; returning the preparation to standard Krebs solution reversed this phenomenon. Dose-resonse curves of muscle contraction in response to acetycholine and KCl administration were shifted upward during FC emulsion superfusion. Frequency of miniature endplate potentials was lower in FC emulsion than that observed in Krebs solution, measured from the same cell of the rat diaphragm. Resting membrane potentials were also greater in muscle cells sampled from FC emulsion-bathed preparations. These data suggest that FC emulsion is superior to standard Krebs solution as a bathing medium for in vitro neuromuscular preparations by virtue of the high solubility of oxygen in it.