48,786 research outputs found
Characterization of a knotted1-like gene of Helianthus tuberosus
No full textSeveral gene families cooperate in meristem signalling; among these Knotted-like Homeobox (KNOX) genes have been shown to play a crucial role. The homeodomain of KNOX genes contains a conserved secondary structure described as "helix-loop-helix-turn-helix" and conserved regions at the N-terminal: the amphipathic helix and the ELK domain. KNOX genes, belonging to the TALE (Three Amino acid Loop Extension) superclass homeobox genes, are further divided into two classes by amino acid sequence differences in the third helix of the homeodomain and distinctive expression patterns. The combined effects of class 1 KNOX genes are required for the prevention of improper stem cell differentiation in the peripheral zone of the SAM. The present work is aimed to characterize the expression pattern of a class 1 KNOX like gene isolated from Helianthus tuberosus (2n = 6x = 10 2) and its involvement on morphogenetic competence expressed by two somaclones (EMB-2 and EMB-9) isolated from the interspecific tetraploid (2n = 4x = 68) hybrid H. annuus x H. tuberosus. The reconstructed full-length cDNA sequence (HtKNOT1, 1398 bp), obtained from 3’ and 5’ RACE, contained a 1089 bp CDS, 54- nucleotides of 5’-untranslated region (UTR), and 255-nucleotides of 3’-UTR. The predicted protein (HtKNOT1) displayed 362 amino acids with a calculated molecular mass of 40.2 kDa. A BLAST search against the protein database of the National Center for Biotechnology Information (NCBI) indicated that the encoded protein shared high sequence identity with members of the class I KNOX subfamily. Sequence information from the HtKNOT1 cDNA was used to design specific primers and to isolate the full-length exons/introns region of the gene. The expression pattern of HtKNOT1 was examined in plants of H. tuberosus by both RT-PCR and in situ hybridisation. HtKNOT1 has been observed to be highly expressed in vegetative shoots and stems. Weak presence of transcripts was detected also in incipient leaf primordia and young leaves. In the last years, it has been demonstrated that the ectopic reactivation of KNOX genes may be sufficient to restore the meristematic potential in differentiated cells. Here, we report that misexpression of HtKNOT1 is intimately linked to the development of ectopic shoots and somatic embryos on leaves of the somaclone EMB-2. Misexpression of HtKNOT1 was also observed in somatic embryos developed from intact adventitious roots of in vitro-grown plantlets of the variant clone EMB-9. The effect of exogenous hormonal treatments on HtKNOT1 expression was evaluated. Notably, massive shoot/embryo regeneration along with a strong accumulation of HtKNOT1 transcripts was induced in EMB-2 non-epiphyllous leaves by in vitro zeatin treatment. However, epiphyllous structures were not formed in zeatin-treated control leaves, despite an enhancement of HtKNOT1 expression, suggesting that HtKNOT1 is not the unique factor, to trigger ectopic morphogenesis in EMB-2 leaves
Measurement of the ratio of branching fractions B(B0→K∗0γ )/B(B0s→φγ ) and the directCP asymmetry inB 0→K∗0γ
No full textThe ratio of branching fractions of the radiative B decays B0→K⁎0γ and B0s→ϕγ has been measured using an integrated luminosity of 1.0 fb−1 of pp collision data collected by the LHCb experiment at a centre-of-mass energy of s√=7TeV. The value obtained is
B(B0→K⁎0γ)B(B0s→ϕγ)=1.23±0.06(stat.)±0.04(syst.)±0.10(fs/fd),
where the first uncertainty is statistical, the second is the experimental systematic uncertainty and the third is associated with the ratio of fragmentation fractions fs/fd. Using the world average value for B(B0→K⁎0γ), the branching fraction B(B0s→ϕγ) is measured to be (3.5±0.4)×10−5.
The direct CP asymmetry in B0→K⁎0γ decays has also been measured with the same data and found to be
ACP(B0→K⁎0γ)=(0.8±1.7(stat.)±0.9(syst.))%.
Both measurements are the most precise to date and are in agreement with the previous experimental results and theoretical expectations
Nuclear changes and cytochemical aspects in olive shoot meristem following the transition to adult phase
No full textDispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
A Study of GUS Expression in Arabidopsis as a Tool for the Evaluation of Gene Evolution, Function and the Role of Expression Derived from Gene Duplication
No full textGene duplication played a fundamental role in eukaryote evolution and different copies of a given gene can be present in extant species, often with expressions and functions differentiated during evolution. We assume that, when such differentiation occurs in a gene copy, this may be indicated by its maintenance in all the derived species. To verify this hypothesis, we compared the histological expression domains of the three β-glucuronidase genes (AtGUS) present in Arabidopsis thaliana with the GUS evolutionary tree in angiosperms. We found that AtGUS gene expression overlaps in the shoot apex, the floral bud and the root hairs. In the root apex, AtGUS3 expression differs completely from AtGUS1 and AtGUS2, whose transcripts are present in the root cap meristem and columella, in the staminal cell niche, in the epidermis and in the proximal cortex. Conversely, AtGUS3 transcripts are limited to the old border-like cells of calyptra and those found along the protodermal cell line. The GUS evolutionary tree reveals that the two main clusters (named GUS1 and GUS3) originate from a duplication event predating angiosperm radiation. AtGUS3 belongs to the GUS3 cluster, while AtGUS1 and AtGUS2, which originate from a duplication event that occurred in an ancestor of the Brassicaceae family, are found together in the GUS1 cluster. There is another, previously undescribed cluster, called GUS4, originating from a very ancient duplication event. While the copy of GUS4 has been lost in many species, copies of GUS3 and GUS1 have been conserved in all species examined
Expression of Spcdc25 in Arabidopsis alters the response of hypocotyl explants to auxin & cytokinin in culture
No full textThe eukaryotic cell cycle comprises four distinct phases, mitosis (M), G1, DNA synthesis (S)-phase and G2 in which the key transitions are G1/S and G2/M. Progression of dividing cells through the cell cycle is controlled by key enzymes: cyclin-dependent kinases (CDKs), the products of cdc2-like genes. The regulation of CDK activity includes, amongst others, its activation by Cdc25 phosphatase at G2/M. This positive regulator is balanced by negative regulation by a protein kinase encoded by wee1. A plant homologue of the inactivating kinase, wee1, has already been cloned. However, a homologue of the activating phosphatase cdc25 has not been unequivocally identified in plants yet. The expression of cdc2-like genes can be influenced by many factors including plant growth regulators, mainly auxins and cytokinins. Expressing the fission yeast cdc25 (Spcdc25) in the tobacco BY2 cell line results in cells bypassing a cytokinin block, and in explants of tobacco expressing Spcdc25, shoot development is stimulated not only in a treatment that favours shoot formation (high cytokinin and low auxin) but also under root-stimulating conditions (high auxin and low cytokinin) and even without exogenous growth regulator treatment. Wild type Arabidopsis hypocotyls explants respond to increasing levels of cytokinin with rapid proliferation, greening and formation of shoots, but are unable to form shoots in the absence of auxin and cytokinin. We tested if hypocotyl explants from Arabidopsis transformed with constitutive and inducible lines Spcdc25 respond like wt to auxin (NAA) and cytokinin (Kinetin) in a system of grids in which we increase concentration of these exogenous plant growth regulators. We find that Wt and Spcdc25 hypocotiles segments are very sensible to higher liveles of ormons (1000 ngml-1 to 3000 ngml-1), calli grew with a lot of root hairs and the analysis of shots formation was impossible. Also is required a minimum level of NAA for calli induction in these strains: at 25 ngml-1 NAA/Kinetin we start to see grow of calli in Spcdc25 lines, plants in WT, not grow in not induced Spcdc25 line. Interesting results at 25, 50 ngml-1 NAA and 200ngml-1 Kinetin where in Spcdc25 there is grow of real roots, not visible in wt and not induced Spcdc25 line. At several concentrations of hormones Spcdc25 forms buds they will be show and discussed
Evidence for the decay B0→J/ψω and measurement of the relative branching fractions of meson decays to J/ψη and J/ψη′
No full textFirst evidence of the B 0 → J / ψ ω decay is found and the B s 0 → J / ψ η and B s 0 → J / ψ η ′ decays are studied using a dataset corresponding to an integrated luminosity of 1.0 fb -1 collected by the LHCb experiment in proton-proton collisions at a centre-of-mass energy of sqrt(s) = 7 TeV. The branching fractions of these decays are measured relative to that of the B 0 → J / ψ ρ 0 decay:frac(B (B 0 → J / ψ ω), B (B 0 → J / ψ ρ 0)) = 0.89 ± 0.19 (stat) - 0.13 + 0.07 (syst),frac(B (B s 0 → J / ψ η), B (B 0 → J / ψ ρ 0)) = 14.0 ± 1.2 (stat) - 1.5 + 1.1 (syst) - 1.0 + 1.1 (frac(f d, f s)),frac(B (B s 0 → J / ψ η ′), B (B 0 → J / ψ ρ 0)) = 12.7 ± 1.1 (stat) - 1.3 + 0.5 (syst) - 0.9 + 1.0 (frac(f d, f s)), where the last uncertainty is due to the knowledge of f d / f s, the ratio of b-quark hadronization factors that accounts for the different production rate of B 0 and B s 0 mesons. The ratio of the branching fractions of B s 0 → J / ψ η ′ and B s 0 → J / ψ η decays is measured to befrac(B (B s 0 → J / ψ η ′), B (B s 0 → J / ψ η)) = 0.90 ± 0.09 (stat) - 0.02 + 0.06 (syst)
Over expression of Spcdc25 and of ATWEE1 in Arabidopsis alter the sensitivity of hypocotyl explants to auxin and cytokinin in culture
No full textThe cell cycle is regulated by plant growth regulators (PGRs), mainly auxins and cytokinins. In eukaryotes, two genes regulate entry into mitosis: cdc25 and wee1, although a confirmed homologue of cdc25 in plants has not yet been identified. Expressing the fission yeast cdc25 (Spcdc25) in tobacco BY2 cells allows them to bypass a cytokinin block at G2/M. In tobacco and Arabidopsis roots, Spcdc25 expression led to an increased frequency of lateral roots. Conversely, over-expression of AtWEE1 in Arabidopsis induces a slower rate of root elongation and a reduced frequency of lateral roots. Wild type Arabidopsis hypocotyl explants respond to increasing levels of cytokinin with rapid proliferation, greening and formation of shoots, but are unable to form shoots in the absence of auxin and cytokinin. We tested if hypocotyl explants from Arabidopsis lines over-expressing ATWEE1 and Spcdc25 respond like WT to auxin (NAA) and cytokinin (Kinetin). We used a system of two-way grids in which we increased concentration of NAA and kinetin in X- and Y-axes, respectively. There were clear differences in the response between the transgenic and WT. All concentrations of auxin and cytokinin suppressed growth of calli in the AtWEE1OE line compared to WT. Moreover, in the AtWEE1OE, both organogenesis and formation of root hair structures were suppressed. At higher PGR levels neither WT nor Spcdc25 lines produced shoots but both produced roots and hairs. A minimum level of NAA was required for callus induction in both WT and Spcdc25 lines. However at low NAA/Kinetin there was growth of calli and more roots in Spcdc25 lines compared with WT. In an inducible Spcdc25 line plus inducer, roots formed at concentrations which suppressed roots in the inducible Spcdc25 line without inducer These results are discussed in the context of plant growth regulators and regulatory genes of the plant cell cycle
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