Hormone interactions and regulation of PsPK2::GUS compared with DR5::GUS and PID::GUS in Arabidopsis thaliana

The putative pea PINOID homolog, PsPK2, is expressed in all growing plant parts and is positively regulated by auxin, gibberellin, and cytokinin. Here, we studied hormonal regulation of PsPK2::GUS expression compared with DR5::GUS and PID::GUS in Arabidopsis. PsPK2::GUS, DR5::GUS, and PID::GUS expression in Arabidopsis shoots is mainly localized in the stipules, hydathodes, veins, developing leaves, and cotyledons. Unlike DR5::GUS, PsPK2::GUS, and PID::GUS are weakly expressed in root tips. Both DR5::GUS and PsPK2::GUS are induced by different auxins and are more sensitive to methyl indole acetic acid, 4-chloro-indole acetic acid, and α-naphthalene acetic acid than others. GA(3) has no significant effect on GUS activity in DR5::GUS-transformed seedlings compared to the control, but induction by auxin and gibberellin in combination is synergistic. Cytokinin increases auxin transport in Arabidopsis seedlings. Auxin, gibberellin, and cytokinin all increase GUS activity in shoots of PsPK2::GUS transformed plants compared to the control. However, only auxin and gibberellin increase GUS activity in PID::GUS shoots. In conclusion, auxin, gibberellin, and cytokinin positively regulate PsPK2 expression in shoots, but not in roots. Auxin and gibberellin also upregulate AtPIN1 and LEAFY expression, which is similar to PsPIN1 and Uni in pea. With minor exceptions, the orthologous genes from both species are regulated similarly.     

Oka: Behind the Barricades: Kanehsatake: 270 Years of Resistance: Spudwrench: Kahnawake Man: My Name is Kahentiiosta: Acts of Defiance

Oka: Behind the Barricades. 1998. 312 minutes. For more information contact the National Film Board of Canada, 3155 Côte de Lisse Rd., St. Laurent, Quebec H4N 2N4. Series of four videos:
Kanehsatake: 270 Years of Resistance. 1993. 120 minutes. Directed by Alanis Obomsawin .
Spudwrench: Kahnawake Man. 1997. 58 minutes. Directed by Alanis Obomsawin .
My Name is Kahentiiosta. 1995. 30 minutes. Directed by Alanis Obomsawin .
Acts of Defiance. 1992. 104 minutes. Directed by Alec MacLeod .     

A dimeric RNA quadruplex architecture comprised of two G:G(:A):G:G(:A) hexads,G:G:G:G tetrads and UUUU loops

Using CD and NMR, we determined the structure of an RNA oligomer, r(GGAGGUUUUGGAGG) (R14), comprising two GGAGG segments joined by a UUUU segment. A modified quadruplex structure was observed for r(GGAGGUUUUGGAGG) in solution even in the absence of K(+). An unusually stable dimeric RNA quadruplex architecture formed from two strands of r(GGAGGUUUUGGAGG) at low K(+) concentration is reported here. In each strand of r(GGAGGUUUUGGAGG), two sets of successive turns in the GGAGG segments and turns at both ends of the UUUU loops drive four G-G steps to align in a parallel manner, a core with two stacked G-tetrads being formed. Two adenine bases bind to two edges of one G:G:G:G tetrad through the sheared G:A mismatch augmenting the tetrad into a G:G(:A):G:G(:A) hexad. Thus, one molecule of r(GGAGGUUUUGGAGG) folds into a modified quadruplex comprising a G:G:G:G tetrad, a UUUU double-chain reversal loop and a G:G(:A):G:G(:A) hexad. Two such molecules further associate by stacking through the dimeric hexad-hexad interface with a rotational symmetry. The ribose rings of most nucleotides take S (close to C2'-endo) puckering, which is unusual for an RNA. K(+) can increase the stability of this quadruplex structure; the number of bound K(+) was estimated from the results of the titration experiment. Besides G:G and G:A mismatches, a network of hydrogen bonds including O4'-NH(2) and C-H..O hydrogen bonds, and the extensive base stacking contribute to the high thermodynamic stability of R14. Our results could provide the stereochemical and thermodynamic basis for elucidating the biological role of the GGAGG-containing RNA segments abundantly existing in various RNAs. Relevance to quadruplex-mediated mRNA-FMRP binding and HIV-1 genome RNA dimerization is discussed.     

Intramolecular higher order packing of parallel quadruplexes comprising a G:G:G:G tetrad and a G(:A):G(:A):G(:A):G heptad of GGA triplet repeat DNA

GGA triplet repeats are widely dispersed throughout eukaryotic genomes and are frequently located within biologically important regions such as gene regulatory regions and recombination hot spot sites. We determined the structure of d(GGA)4 (12-mer) under physiological conditions and founded the formation of an intramolecular parallel quadruplex for the first time. Later, a similar architecture to that of the intramolecular parallel quadruplex was found for a telomere DNA in the crystalline state. Here, we have determined the structure of d(GGA)8 (24-mer) under physiological conditions. Two intramolecular parallel quadruplexes comprising a G:G:G:G tetrad and a G(:A):G(:A):G(:A):G heptad are formed in d(GGA)8. These quadruplexes are packed in a tail-to-tail manner. This is the first demonstration of the intramolecular higher order packing of quadruplexes at atomic resolution. K+ ions, but not Na+ ones, are critically required for the formation of this unique structure. The elucidated structure suggests the mechanisms underlying the biological events related to the GGA triplet repeat. Furthermore, in the light of the structure, the mode of the higher order packing of the telomere DNA is discussed.     

Experimental demonstration of T:(G:G:G:G):T hexad and T:A:A:T tetrad alignments within a DNA quadruplex stem

A template-based approach was used to design unprecedented architectural motifs into a known DNA framework. The structure formed by the sequence d(GCGGTTGGAT) in 0.1 M Na(+) solution has been determined using molecular dynamics simulations constrained by distance and dihedral restraints derived from NMR experiments. The molecular topology has been previously observed for the sequence d(GCGGTGGAT) (Webba da Silva, M. (2003) Biochemistry 42, 14356-65). Insertion of a single thymine into the double chain reversal formed by the segment GGTGG results in the unprecedented experimental demonstration of a T:(G:G:G:G):T hexad. The bi-stranded hexad results from the pairing alignment of two G(T-G) triads. Each triad results from recognition of the sheared edge of a guanine by the Watson-Crick edge of a thymine of the segment GGTTGG. The alignment is stabilized by base-stacking of the thymine to the sugar pucker of the preceding thymine. The latter is involved in formation of the T:A:A:T tetrad alignment by forming a hydrogen bond with the free amino proton of a Watson-Crick aligned A:A mispair. We have thus established that residues in double chain reversal loops linking juxtaposed tetrads of a quadruplex stem may facilitate formation of yet unknown hydrogen bond alignments. By employing a systematic approach analysis of sequence motifs appearing in double chain reversals, bridging tetrad layers should allow for the prediction of topologies and architectural motifs appearing in biologically relevant genomic regions.     

Leaf lipids of Ribes nigrum: a plant containing 16:3, alpha-18:3, gamma-18:3 and 18:4 fatty acids

The glycerolipid composition of Ribes nigrum (blackcurrant) leaves was determined. The total fatty acid composition was unusual in that alpha-linolenic acid (alpha-18:3) occurred together with cis-7,10,13-hexadecatrienoic acid (16:3) and lower amounts of stearidonic acid (18:4) and gamma-linolenic acid (gamma-18:3). Monogalactosyldiacylglycerol contained the highest proportion of 16:3 with less in digalactosyldiacylglycerol. gamma-18:3 and 18:4 were present in all lipids and 18:4 was always greater than gamma-18:3. The highest percentages of gamma-18:3 and 18:4 were in phosphatidylcholine, but phosphatidylglycerol was particularly low in these acids. In summary, the lipid composition was largely typical of 16:3 plants but there was a minor contribution typical of 18:4 plants. The possibility of three pathways for glycolipid biosynthesis is discussed.     

Systematics and biogeography of the subantarctic Leptusa (Coleoptera: Staphylinidae: Aleocharinae: Homalotini)

Leptusa atriceps and L. antarctica, flightess representatives of the nearly global genus Leptusa in the remote and widely distributed subantarctic islands, are taxonomically revised. Identity and the widely disjunct distribution of L. atriceps on Falkland, South Georgia, Marion, Crozet and Kerguelen Islands are confirmed. Leptusa antarctica is found to be a complex of five species restricted to the subantarctic islands of New Zealand. Two of these species, L. sparsepunctata and L. nesiotes are here reinstated from synonymy and two others, Leptusa insulae sp. nov. and Leptusa steeli sp. nov., are described as new to science. The monophyly of subantarctic Leptusa species united in the subgenus Halmaeusa was determined by a phylogenetic study of five exemplar homalotine genera and 17 representatives of Leptusa from South America and the Holarctic based on 76 adult morphological characters. Phylogenetic placement of Halmaeusa was not firmly established. Nanoglossa, a temperate South American subgenus of Leptusa was found as a possible sister group to Halmaeusa. The distribution of Halmaeusa species with two to four species that occur sympatrically on Campbell and Auckland Islands, and other species distributed across several remote islands, provides a framework for future biogeographic study of the subantarctic Leptusa.

http://www.zoobank.org/urn:lsid:zoobank.org:act:82509B9D-4BF6-47E1-B6F7-396ED193A0FA; http://www.zoobank.org/urn:lsid:zoobank.org:act:40A3D6FC-27FF-4070-88CA-1B519ABE760A     

Quadruplexes of human telomere DNA analogs designed to contain G:A:G:A,G:G:A:A,and A:A:A:A tetrads

Replacement of two to four guanines by adenines in the human telomere DNA repeat dG₃(TTAG₃)₃ did not hinder the formation of quadruplexes if the substitutions took place in the terminal tetrad bridged by the diagonal loop of the intramolecular antiparallel three‐tetrad scaffold, as proved by CD and PAGE in both Na⁺ and K⁺ solutions. Thermodynamic data showed that, in Na⁺ solution, the dG₃(TTAG₃)₃ quadruplex was destabilized, the least by the two G:A:G:A tetrads, the most by the G:G:A:A tetrad in which the adenosines replaced syn‐guanosines. In physiological K⁺ solution, the highest destabilization was caused by the 4A tetrad. In K⁺, only the unmodified dG₃(TTAG₃)₃ quadruplex rearranged into a K⁺‐dependent quadruplex form, none of the multiple adenine‐modified structures did so. This may imply biological consequences for nonrepaired A‐for‐G mutations. © 2010 Wiley Periodicals, Inc. Biopolymers 93: 880–886, 2010.     

Association of DNA quadruplexes through G:C:G:C tetrads. Solution structure of d(GCGGTGGAT)

The structure formed by the DNA sequence d(GCGGTGGAT) in a 100 mM Na(+) solution has been determined using molecular dynamics calculations constrained by distance and dihedral restraints derived from NMR experiments performed at isotopic natural abundance. The sequence folds into a dimer of dimers. Each symmetry-related half contains two parallel stranded G:G:G:G tetrads flanked by an A:A mismatch and by four-stranded G:C:G:C tetrads. Each of the two juxtaposed G:C:G:C tetrads is composed of alternating antiparallel strands from the two halves of the dimer. For each single strand, a thymine intersperses a double chain reversal connecting the juxtaposed G:G:G:G tetrads. This architecture has potential implications in genetic recombination. It suggests a pathway for oligomerization involving association of quadruplex entities through GpC steps.     

Platelet adhesiveness and aggregation: the collagen:glycosyl, polypeptide:N-acetylgalactosaminyl and glycoprotein:galactosyl transferases of human platelets

Four glycoprotein:glycosyl transferases were identified, purified, and characterized from human platelets. The enzymes present were collagen:glc, collagen:gal, polypeptide:galNAc, and glycoprotein:gal; the fetuin:glcNAc transferase was absent. Each of the 4 transferases was found to be almost exclusively bound to the platelet plasma membrane. Incubation of platelet homogenates without exogenous acceptors yielded no transfer of monosaccharide, indicating the complete lack of endogenous acceptors. These results lead to the interesting speculation that the transferases may not be responsible in the mature platelet for glycoprotein synthesis at all, but rather that they may function for intercellular adhesion and the primary step in hemostasis, the adhesion of collagen to platelets.     

d(CGGTGGT) forms an octameric parallel G-quadruplex via stacking of unusual G(:C):G(:C):G(:C):G(:C) octads

Among non-canonical DNA secondary structures, G-quadruplexes are currently widely studied because of their probable involvement in many pivotal biological roles, and for their potential use in nanotechnology. The overall quadruplex scaffold can exhibit several morphologies through intramolecular or intermolecular organization of G-rich oligodeoxyribonucleic acid strands. In particular, several G-rich strands can form higher order assemblies by multimerization between several G-quadruplex units. Here, we report on the identification of a novel dimerization pathway. Our Nuclear magnetic resonance, circular dichroism, UV, gel electrophoresis and mass spectrometry studies on the DNA sequence dCGGTGGT demonstrate that this sequence forms an octamer when annealed in presence of K(+) or NH(4)(+) ions, through the 5'-5' stacking of two tetramolecular G-quadruplex subunits via unusual G(:C):G(:C):G(:C):G(:C) octads.     

Analysis of Erwinia chrysanthemi EC16 pelE::uidA, pelL::uidA, and hrpN::uidA mutants reveals strain-specific atypical regulation of the Hrp type III secretion system

The plant pathogen Erwinia chrysanthemi produces a variety of factors that have been implicated in its ability to cause soft-rot diseases in various hosts. These include HrpN, a harpin secreted by the Hrp type III secretion system; PelE, one of several major pectate lyase isozymes secreted by the type II system; and PelL, one of several secondary Pels secreted by the type II system. We investigated these factors in E. chrysanthemi EC16 with respect to the effects of medium composition and growth phase on gene expression (as determined with uidA fusions and Northern analyses) and effects on virulence. pelE was induced by polygalacturonic acid, but pelL was not, and hrpN was expressed unexpectedly in nutrient-rich King's medium B and in minimal salts medium at neutral pH. In contrast, the effect of medium composition on hrp expression in E. chrysanthemi CUCPB1237 and 3937 was like that of many other phytopathogenic bacteria in being repressed in complex media and induced in acidic pH minimal medium. Northern blot analysis of hrpN and hrpL expression by the wild-type and hrpL::omegaCmr and hrpS::omegaCmr mutants revealed that hrpN expression was dependent on the HrpL alternative sigma factor, whose expression, in turn, was dependent on the HrpS putative sigma54 enhancer binding protein. The expression of pelE and hrpN increased strongly in late logarithmic growth phase. To test the possible role of quorum sensing in this expression pattern, the expI/expR locus was cloned in Escherichia coli on the basis of its ability to direct production of acyl-homoserine lactone and then used to construct expI mutations in pelE::uidA, pelL::uidA, and hrpN::uidA Erwinia chrysanthemi strains. Mutation of expI had no apparent effect on the growth-phase-dependent expression of hrpN and pelE, or on the virulence of E. chrysanthemi in witloof chicory leaves. Overexpression of hrpN in E. chrysanthemi resulted in approximately 50% reduction of lesion size on chicory leaves without an effect on infection initiation.     

Molecular species of phosphatidylcholine in abetalipoproteinemia: effect of lecithin:cholesterol acyltransferase and lysolecithin acyltransferase

In order to study the role of very low density lipoproteins (VLDL) and low density lipoproteins (LDL) in determining the molecular species composition of phosphatidylcholine (PC) and the specificity of lecithin:cholesterol acyltransferase (LCAT) in human plasma, we studied the PC species composition in plasma from abetalipoproteinemic (ABL) and control subjects before and after incubation at 37 degrees C. The ABL plasma contained significantly higher percentages of sn-2-18:1 species (16:0-18:1, 18:0-18:1, and 18:1-18:1) and lower percentages of sn-2-18:2 species (16:0-18:2, 18:0-18:2, and 18:1-18:2) as well as sn-2-20:4 species (16:0-20:4, 18:0-20:4, and 18:1-20:4). Similar abnormalities were found in the PC of ABL erythrocytes, while the PE of the erythrocytes was less affected. The relative contribution of various PC species towards LCAT reaction in ABL plasma was significantly different from that found in normal plasma. Thus, while 16:0-18:2 and 16:0-18:1 contributed, respectively, 43.8% and 15.9% of the total acyl groups used for cholesterol esterification in normal plasma, they contributed, respectively, 21.5% and 37.9% in ABL plasma. The relative contribution of 16:0-20:4 was also significantly lower in ABL plasma (4.7% vs. 9.0% in normal), while that of 16:0-16:0 was higher (6.4% vs. 0.5%). However, the selectivity factors of various species (percent contribution/percent concentration) were not significantly different between ABL and normal plasma, indicating that the substrate specificity of LCAT is not altered in the absence of VLDL and LDL. Incubation of ABL plasma in the presence of normal VLDL or LDL resulted in normalization of its molecular species composition and in the stimulation of its LCAT activity. Addition of LDL, but not VLDL, also resulted in the activation of lysolecithin acyltransferase (LAT) activity. The incorporation of [1-14C]palmitoyl lysoPC into various PC species in the presence of LDL was similar to that observed in normal plasma, with the 16:0-16:0 species having the highest specific activity. These results indicate that the absence of apoB-containing lipoproteins significantly affects the molecular species composition of plasma PC as well as its metabolism by LCAT and LAT reactions.     

Subject: Distribution: Influence of biotic and abiotic factors

Research Notes on Avian Biology 1994: Selected Contributions from the 21st International Ornithological CongressEcology: Distribution

Subject: Distribution: Influence of biotic and abiotic factors     

An intramolecular quadruplex of (GGA)(4) triplet repeat DNA with a G:G:G:G tetrad and a G(:A):G(:A):G(:A):G heptad, and its dimeric interaction.

The structure of d(GGAGGAGGAGGA) containing four tandem repeats of a GGA triplet sequence has been determined under physiological K(+) conditions. d(GGAGGAGGAGGA) folds into an intramolecular quadruplex composed of a G:G:G:G tetrad and a G(:A):G(:A):G(:A):G heptad. Four G-G segments of d(GGAGGAGGAGGA) are aligned parallel with each other due to six successive turns of the main chain at each of the GGA and GAGG segments. Two quadruplexes form a dimer stabilized through a stacking interaction between the heptads of the two quadruplexes. Comparison of the structure of d(GGAGGAGGAGGA) with the reported structure of d(GGAGGAN) (N=G or T) containing two tandem repeats of the GGA triplet revealed that although the two structures resemble each other to some extent, the extension of the repeats of the GGA triplet leads to distinct structural differences: intramolecular quadruplex for 12-mer versus intermolecular quadruplex for 7-mer; heptad versus hexad in the quadruplex; and three sheared G:A base-pairs versus two sheared G:A base-pairs plus one A:A base-pair per quadruplex. It was also suggested that d(GGAGGAGGAGGA) forms a similar quadruplex under low salt concentration conditions. This is in contrast to the case of d(GGAGGAN) (N=G or T), which forms a duplex under low salt concentration conditions. On the basis of these results, the structure of naturally occurring GGA triplet repeat DNA is discussed.     

Valproic acid phase shifts the rhythmic expression of Period2::Luciferase

Valproic acid (VPA) is an anticonvulsant used to treat bipolar disorder, a psychiatric disease associated with disturbances in circadian rhythmicity. Little is known about how VPA affects circadian rhythms. The authors cultured tissues containing the master brain pacemaker for circadian rhythmicity, the suprachiasmatic nuclei (SCN), and skin fibroblasts from transgenic PERIOD2::LUCIFERASE (PER2::LUC) mice and studied the effect of VPA on the circadian PER2::LUC rhythm by measuring bioluminescence. VPA (1 mM) significantly phase advanced the PER2::LUC rhythm when applied at a time point corresponding to the lowest (trough, ~ZT 0) PER2::LUC expression but phase delayed the PER2::LUC rhythm when the drug was administered at the time of highest (peak, ~ZT 12) protein expression. In addition, it significantly increased the overall amplitude of PER2::LUC oscillations at time points at or close to ZT 12 but had no effect on period. Real-time PCR analyses on mouse and human fibroblasts revealed that expressions of other clock genes were increased after 2 h treatment with VPA. Because VPA is known to inhibit histone deacetylation, the authors treated cultures with an established histone deacetylation inhibitor, trichostatin A (TSA; 20 ng/mL), to compare the effect of VPA and TSA on molecular rhythmicity. They found that TSA had similar effects on the PER2::LUC rhythm as VPA. Furthermore, VPA and TSA significantly increased acetylation on histone H3 but in comparison little on histone H4. Lithium is another commonly used treatment for bipolar disorder. Therefore, the authors also studied the impact of lithium chloride (LiCl; 10 mM) on the PER2::LUC rhythm. LiCl delayed the phase, but in contrast to VPA and TSA, LiCl lengthened the PER2::LUC period and had no effect on histone acetylation. These results demonstrate that VPA can delay or advance the phase, as well as increase the amplitude, of the PERIOD2::LUCIFERASE rhythm depending on the circadian time of application. Furthermore, the authors show that LiCl delays the phase and lengthens the period of the PER2::LUC rhythm, confirming previous reports on circadian lithium effects. These different molecular effects may underlie differential chronotherapeutic effects of VPA and lithium.     

Review article: The Aboriginal experience: A problem of interpretation

Raymond Evans, Kay Saunders and Kathryn Cronin, RACE RELATIONS IN COLONIAL QUEENSLAND: A HISTORY OF EXCLUSION, EXPLOITATION AND EXTERMINATION, St. Lucia: University of Queensland Press, 1988 (fp.1975), 450 pp., $26.95.

Henry Reynolds, WITH THE WHITE PEOPLE: THE CRUCIAL ROLE OF ABORIGINES IN THE EXPLOITATION AND DEVELOPMENT OF AUSTRALIA, Ringwood: Penguin Books, 1990, 288 pp., $16.99.

Jeff Collmann, FRINGE‐DWELLERS AND WELFARE: THE ABORIGINAL RESPONSE TO BUREAUCRACY, St. Lucia: University of Queensland Press, 1988, 276 pp., $29.95.     

Seaweed biogeochemistry: Global assessment of C:N and C:P ratios and implications for ocean afforestation

Algal carbon-to-nitrogen (C:N) and carbon-to-phosphorus (C:P) ratios are fundamental for understanding many oceanic biogeochemical processes, such as nutrient flux and climate regulation. We synthesized literature data (444 species, >400 locations) and collected original samples from Tasmania, Australia (51 species, 10 locations) to update the global ratios of seaweed carbon-to-nitrogen (C:N) and carbon-to-phosphorus (C:P). The updated global mean molar ratio for seaweed C:N is 20 (ranging from 6 to 123) and for C:P is 801 (ranging from 76 to 4102). The C:N and C:P ratios were significantly influenced by seawater inorganic nutrient concentrations and seasonality. Additionally, C:N ratios varied by phyla. Brown seaweeds (Ochrophyta, Phaeophyceae) had the highest mean C:N of 27.5 (range: 7.6–122.5), followed by green seaweeds (Chlorophyta) of 17.8 (6.2–54.3) and red seaweeds (Rhodophyta) of 14.8 (5.6–77.6). We used the updated C:N and C:P values to compare seaweed tissue stoichiometry with the most recently reported values for plankton community stoichiometry. Our results show that seaweeds have on average 2.8 and 4.0 times higher C:N and C:P than phytoplankton, indicating seaweeds can assimilate more carbon in their biomass for a given amount of nutrient resource. The stoichiometric comparison presented herein is central to the discourse on ocean afforestation (the deliberate replacement of phytoplankton with seaweeds to enhance the ocean biological carbon sink) by contributing to the understanding of the impact of nutrient reallocation from phytoplankton to seaweeds under large-scale seaweed cultivation.