Mechanism of ATP hydrolysis by sarcoplasmic reticulum and the role of phospholipids.

Exchange of sarcoplasmic reticulum phospholipids with dipalmitoyllecithin inhibits the (Mg2+ + Ca2+)-activated ATPase activity below 40 degrees by inhibition of the decomposition of phosphoprotein intermediate. The rate of phosphoprotein formation and the steady state concentration of phosphoprotein measured by rapid kinetic techniques are affected to a lesser extent. The inhibitory effect of dipalmitoyllecithin on ATPase activity is probably related to the viscosity of the hydrocarbon region of the membrane which inhibits the conformational change leading to calcium translocation and the eventual cleavage of phosphoprotein.     

Enzymes of ammonia assimilation in legume nodules: A comparison between ureide- and amide-transporting plants

Levels of amide and ureide biogenic enzymes were compared in the plant cytosol fractions of root nodules from soybean ( Glycine max L. Merr., cv. Williams), pintobean ( Phaseolus vulgaris L. cv. Pinto) and Lupin ( Lupinus angustifolius L. cv. Frost). Enzymes of purine oxidation were found to be present in significant quantities only in ureide-transporting pintobean and soybean nodules. The levels of these enzymes were low in lupin, but this amide-exporter had significantly higher levels of asparagine synthetase. Enzymes of de novo purine biosynthesis and glycine biosynthesis were present at higher levels in pintobean and soybean, consistent with a role for de novo purine biosynthesis in ureide biogenesis. The low levels of these enzymes in lupin are consistent with a role in general purine and amino acid metabolism in these nodules, not directly related to the synthesis of transport compounds for fixed atmospheric nitrogen. Amino acid concentrations in soybean, pintobean and lupin nodules reflected the metabolic differences between amide and ureide plants. The comparative data presented are consistent with a pathway of ureide biogenesis using glutamine, glutamate and aspartate synthesized via reactions catalyzed by glutamine synthetase, glutamate synthase and aspartate aminotransferase in the de novo synthesis of purines followed by oxidation of these purines to produce the ureides allantoin and allantoic acid.     

Effect of temperature on seed production in the invasive grass Glyceria maxima (Hartm.) Holmb. (Poaceae) in South Africa

Temperature is one of the main factors that determine sexual reproduction in terrestrial and emergent aquatic plant species. The effect of temperature on sexual reproduction and seed production of Glyceria maxima (Hartm.) Holmb. in the southern hemisphere is unknown. Glyceria maxima collections in February 2010 at three isolated infestations in KwaZulu-Natal failed to yield a single seed, only empty panicles. Laboratory experiments showed that vernalisation had no consistent effect on seed production. Field- and laboratory-grown plants produced seeds in the 2010/2011 season, because of having sufficient time at optimum temperatures required for seed production (1 491 and 1 585 hours, respectively), compared to a shorter period (1 352 hours) of suitable temperatures during the 2009/2010 growing season. An inadequate period of optimum temperatures (15–25°C) during seed production resulted in the lack of seeds in the field in the 2009/2010 growing season. This study showed that temperature and duration of exposure thereto during the seed-production period play vital roles in G. maxima sexual reproduction.     

A subset of chemosensory genes differs between two populations of a specialized leaf beetle after host plant shift

Due to its fundamental role in shaping host selection behavior, we have analyzed the chemosensory repertoire of Chrysomela lapponica. This specialized leaf beetle evolved distinct populations which shifted from the ancestral host plant, willow (Salix sp., Salicaceae), to birch (Betula rotundifolia, Betulaceae). We identified 114 chemosensory candidate genes in adult C. lapponica: 41 olfactory receptors (ORs), eight gustatory receptors, 17 ionotropic receptors, four sensory neuron membrane proteins, 32 odorant binding proteins (OBPs), and 12 chemosensory proteins (CSP) by RNA‐seq. Differential expression analyses in the antennae revealed significant upregulation of one minus‐C OBP (ClapOBP27) and one CSP (ClapCSP12) in the willow feeders. In contrast, one OR (ClapOR17), four minus‐C OBPs (ClapOBP02, 07, 13, 20), and one plus‐C OBP (ClapOBP32) were significantly upregulated in birch feeders. The differential expression pattern in the legs was more complex. To narrow down putative ligands acting as cues for host discrimination, the relative abundance and diversity of volatiles of the two host plant species were analyzed. In addition to salicylaldehyde (willow‐specific), both plant species differed mainly in their emission rate of terpenoids such as (E,E)‐α‐farnesene (high in willow) or 4,8‐dimethylnona‐1,3,7‐triene (high in birch). Qualitatively, the volatiles were similar between willow and birch leaves constituting an “olfactory bridge” for the beetles. Subsequent structural modeling of the three most differentially expressed OBPs and docking studies using 22 host volatiles indicated that ligands bind with varying affinity. We suggest that the evolution of particularly minus‐C OBPs and ORs in C. lapponica facilitated its host plant shift via chemosensation of the phytochemicals from birch as novel host plant.     

S. aureus Evades Macrophage Killing through NLRP3-Dependent Effects on Mitochondrial Trafficking

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Marmoset phylogenetics, conservation perspectives, and evolution of the mtDNA control region

Marmosets (genus Callithrix) are a diverse group of platyrrhine primates with 13-15 purported taxa, many of them considered endangered. Morphological analyses constitute most of the basis for recognition of these forms as distinct taxa. The purpose of this study was to provide a molecular view, based on mitochondrial control region sequences, of the evolutionary history of the marmosets, concomitant with a molecular phylogenetic perspective on species diversity within the group. An additional purpose was to provide the first comparative examination of a complete New World monkey control region sequence with those of other mammals. The phylogenetic analyses provide convincing support for a split between the Atlantic forest and Amazonian marmosets, with the inclusion of the pygmy marmoset (Cebuella pygmaea) at the base of the Amazonian clade. The earliest branch of the Atlantic forest group was C. aurita. In the Amazonian group, the analyses do not support the recognition of C. humeralifer and the recently described C mauesi as distinct taxa. They do, however, support a clear distinction between C. argentata and a strongly supported mixed clade of C. humeralifer and C. mauesi. In the Atlantic forest group, the phylogenetic tree suggests mixing between C. penicillata, C. kuhli, and possibly C. jacchus. Most of the sequence features characteristic of other mammal control regions were also evident in marmosets, with the exception that conserved sequence blocks (CSBs) 2 and 3 were not clearly identifiable. Tandem repeat units often associated with heteroplasmy in a variety of other mammals were not evident in the marmoset sequences.      

Persistent nuclear ribosomal DNA sequence polymorphism in the Amelanchier agamic complex (Rosaceae)

Individual plants of several Amelanchier taxa contain many polymorphic nucleotide sites in the internal transcribed spacers (ITS) of nuclear ribosomal DNA (nrDNA). This polymorphism is unusual because it is not recent in origin and thus has resisted homogenization by concerted evolution. Amelanchier ITS sequence polymorphism is hypothesized to be the result of gene flow between two major North American clades resolved by phylogenetic analysis of ITS sequences. Western North American species plus A. humilis and A. sanguinea of eastern North America form one clade (A), and the remaining eastern North American Amelanchier make up clade B. Five eastern North American taxa are polymorphic at many of the nucleotide sites where clades A and B have diverged and are thought to be of hybrid origin, with A. humilis or A. sanguinea as one parent and various members of clade B as the other parent. Morphological evidence suggests that A. humilis is one of the parents of one of the polymorphic taxa, a microspecies that we refer to informally as A. "erecta." Sequences of 21 cloned copies of the ITS1- 5.8S gene-ITS2 region from one A. "erecta" individual are identical to A. humilis sequence or to the clade B consensus sequence, or they are apparent recombinants of A. humilis and clade B ITS repeats. Amelanchier "erecta" and another polymorphic taxon are suspected to be relatively old because both grow several hundred kilometers beyond the range of one of their parents. ITS sequence polymorphisms have apparently persisted in these two taxa perhaps because of polyploidy and/or agamospermy (asexual seed production), which are prevalent in the genus.      

Assessment of viability and mitochondrial function of equine spermatozoa using double staining and flow cytometry

An objective double-staining method was developed to evaluate viability and mitochondrial function of stallion spermatozoa using flow cytometry. Sperm viability was assessed by propidium iodide (PI) exclusion, and mitochondrial function was measured by the intensity of rhodamine 123 (R123) fluorescence. Flow cytometry estimates of sperm viability measured by PI were equivalent (P > 0.05) to estimates made using Hoechst 33258 stain and fluorescent microscopy (% dead: 25 +/- 2.4 vs 21.5 +/- 3.5). The use of both PI and R123 was validated by addition of various proportions of freeze-shocked (membrane damaged) cells to viable spermatozoa. There was a high correlation (r(2) = 0.996) between increased PI positivestained (dead) cells and the number of membrane-damaged spermatozoa added (% dead: 29 +/- 0.4, 44 +/- 1.4, 58 +/- 0.9, 75 +/- 0.7 and 91+/- 0.25 vs 0, 25, 50, 75 and 100% damaged cells, respectively). Optimal mitochondrial activity (OMA), as assessed by R123 uptake, was also reduced proportionally (r(2) = 0.976) by the percentage of membrane-damaged cells added (% OMA: 48 +/- 0.6, 37 +/- 1.7, 29 +/- 0.5, 16 +/- 1, 3.8 +/- 1.3 vs 0, 25, 50, 75 and 100% damaged cells, respectively). The mitochondrial inhibitors rotenone and monensin significantly depressed optimal mitochondrial activity (P < 0.001), and there was a significant positive correlation (r(2) = 0.959) between the dose of inhibitors added and the population of sperm cells exhibiting minimal R123 staining (4 -/+ 0.9, 12 -/+ 1.6, 14 -/+ 0.1 and 28 -/+ 2% for treatments with 0, 0.5, 1 and 2 x 10(-5) M rotenone and 0, 0.5, 1, and 2 x 10(-4) M monensin, respectively). Finally, it was shown that treatments containing identical proportions of membrane-damaged cells yielded similar results in terms of viability and mitochondrial activity, irrespective of whether the staining procedure was single or double (P > 0.05). The results of the double-staining method revealed that the percentage of spermatozoa with optimally functioning mitochondria was significantly correlated with the percentage of viable (PI negative) sperm cells (r(2) = 0.998). Flow cytometric analyses using this staining procedure provides reliable and rapid (10,000 cells/min) qualitative assessment of stallion semen.