1,360 research outputs found
Phytoplasma effectors and pathogenicity factors
No full textFor the study and the management of phytoplasma-associated diseases,
the most relevant knowledge needed is the one related to their pathogenicity. After
the availability of full and draft genome sequences of some of the phytoplasmas, a
mining search allowed identifying a number of possible virulence factors. Their
possible pathogenic action was verified mainly by their expression in transgenic
plants such as Arabidopsis spp. and Nicotiana spp. Several possible pathogenicity
factors such as TENGU and SAP11 and/or effector molecules were shown to be
related to metabolic and or phenotypic modifications indistinguishable from those
present in the phytoplasma-infected plants such as phyllody and witches’ broom.
The possible pathogenicity factors or disease effectors studied enclosing extrachromosomal
DNAs, phloem structural modifications, and very recently miRNAs are
also described
Dissecting the multifaceted mechanisms that drive leafhopper host-phytoplasma specificity.
No full textPlant pathogen-vector complexes cause some of the most important diseases of crops worldwide, and are among the most difficult to manage effectively. Novel strategies are now needed for their management based on mechanistic understanding of transmission processes. Since the publication by Academic Press of a four-volume series on Vector Biology by Maramorosch et al during the 1970-80’s’s there have been no follow-on reference books that offer a contemporary treatment of pathogen-vector interactions and vector biology. The chapters in the proposed book will be written by well-known vector biologists from the fields of entomology and plant virology and pathology, in the instances for which it was possible, the authors together represent both perspectives. Several chapters are authored by experts outside the arena of vector interactions, but bring valuable, cross-disciplinary perspectives to relevant aspects of many vector-transmission systems, in particular the chapter on saliva and chemical ecology of plant vector-host interactions. The inclusion of chapterlets on ‘emerging pathogen-complexes is suggested in order to raise awareness of these newly occurring diseases that remain poorly studied and whose inclusion in the book will highlight the need for attention by the community. In any case, each author brings expertise and breadth in pathogen-vector interactions in distinct focus areas. For certain systems the level of knowledge is in its infancy (emergent), while for others specific molecular and cellular components are well known to govern the transmission processes, while others are in intermediate stages of elucidation. A Glossary of Terms is planned and Elaine Backus (entomology, feeding behavior) has agreed to take the lead on this section and J.K. Brown will work with her to bring the virology perspective
A single-bit and double-adjacent error correcting parallel decoder for multiple-bit error correcting BCH codes
No full textThis paper presents a novel high-speed BCH decoder that corrects double-adjacent and single-bit errors in parallel and serially corrects multiple-bit errors other than double-adjacent errors. Its operation is based on extending an existing parallel BCH decoder that can only correct single-bit errors and serially corrects double-adjacent errors at low speed. The proposed de- coder is constructed by a novel design and is suitable for nanoscale memory systems, in which multiple-bit errors occur at a probability comparable to single-bit errors and double-adjacent errors occur at a higher probability (nearly two orders of magnitude) than other multiple-bit errors. Extensive simulation results are reported. Compared with the existing scheme, the area and de- lay time of the proposed decoder are on average 11% and 6% higher, but its power consumption is reduced by 9% on average. This paper also shows that the area, delay, and power overheads incurred by the proposed scheme are significantly lower than traditional fully parallelized BCH decoders capable of correcting any double-bit errors in parallel
The groEL gene as an additional marker for finer differentiation of ‘Candidatus Phytoplasma asteris'-related strains
No full textPhytoplasma classification established using 16S ribosomal groups and
‘Candidatus Phytoplasma’ taxon are mainly based on the 16S rDNA properties and do not always provide molecular distinction of the closely related strains such as those in the aster yellows group (16SrI or ‘Candidatus Phytoplasma asteris’-related strains). Moreover, because of the highly conserved nature of the 16S rRNA gene, and of the not uncommon presence of 16S rDNA interoperon sequence heterogeneity, more variable single copy genes, such as ribosomal protein (rp), secY and tuf, were shown to be suitable for differentiation of closely related phytoplasma strains. Specific amplification of fragments containing phytoplasma groEL allowed studying its variability in 27 ‘Candidatus Phytoplasma asteris’-related strains belonging to different 16SrI subgroups, of which 11 strains were not studied before and 8 more were not studied on other genes than 16S rDNA. The restriction fragment length polymorphism (RFLP) analyses of the amplified fragments confirmed differentiation among 16SrI-A, I-B, I-C, I-F and I-P subgroups, and showed further differentiation in strains assigned to 16SrI-A, 16SrI-B and 16SrI-C
subgroups. However, analyses of groEL gene failed to discriminate strains in subgroups 16SrI-L and 16SrI-M (described on the basis of 16S rDNA interoperon sequence heterogeneity) from strains in subgroup 16SrI-B. On the contrary, the 16SrI unclassified strain ca2006/5 from carrot (showing interoperon sequence heterogeneity) was differentiable on both rp and groEL genes from the strains in subgroup 16SrI-B. These results indicate that interoperon sequence heterogeneity of strains AY2192, PRIVA (16SrI-L), AVUT (16SrI-M) and ca2006/5 resulted inmultigenic changes – one evolutionary step
further – only in the latter case. Phylogenetic analyses carried out on groEL are in agreement with 16Sr, rp and secY based phylogenies, and confirmed the differentiation obtained by RFLP analyses on groEL amplicons
Effects of insulin on hexose transport across blood-brain barrier in normoglycemia
No full textThe effects of insulin on 3-O-[14C]methylglucose transport across the blood-brain barrier (BBB) were studied in conscious rats under steady-state normoglycemic conditions. The [14C]methylglucose was infused intravenously at a constant rate, and animals were killed at various times between 5 and 30 min after the initiation of the infusion. The time course of the arterial plasma concentration of [14C]methylglucose was determined in timed arterial blood samples taken during the infusion. Local cerebral tissue concentrations of [14C]methylglucose at the time of killing were determined by quantitative autoradiography of brain sections. The rate constants for inward and outward transport of [14C]methylglucose across the BBB, K1, and k2, respectively, were estimated by a least-squares, best-fit of a kinetic equation to the measured time courses of plasma and tissue concentrations. K1 and k2 were reduced by an average of 24 and 31%, respectively, in gray matter and 7 and 16% in white matter from values estimated similarly in normal insulinemic control rats. The equilibrium distribution ratio, K1/k2, for [14C]methylglucose in brain increased by approximately 10-11% in the hyperinsulinemic animals. Because 3-O-[14C]methylglucose shares the same carrier that transports glucose and other hexoses across the BBB, these results suggest that hyperinsulinemia decreases the rate constants for transport but increases the distribution space for hexoses in brain. These effects are, however, quite small and are probably minor or negligible when compared with the major effects of insulin in other tissues
The cpn60 gene as an additional marker for 'Candidatus Phytoplasma asteris' strain differentiation.
No full textThe phytoplasma classification was firstly established using RFLP analysis with a number of restriction enzymes on 1,200 bp amplicons in their 16S rDNA. Obtained phytoplasma 16Sr groups have been shown to be consistent with the groups (clades) defined by phylogenetic analysis of near-full-length 16S rRNA gene sequences, confirming phylogenetical validity of this grouping. However the recent introduction of ‘Candidatus’ status, which is based on 16S sequences, does not always provides the molecular distinction necessary for epidemiological studies towards disease control. For ‘Candidatus Phytoplasma asteris’-related phytoplasmas numerous different diseases, plant species and insect vectors were described and attributed to different 16SrI subgroups. However because of the highly conserved nature of the 16S rRNA gene, and of the not uncommon presence of 16S rDNA interoperon sequence heterogeneity, more variable single copy genes were often shown to be more suitable for finer phytoplasma differentiation. Additional genes such as ribosomal protein (rp), secY, tuf, have been used for ‘Ca. P. asteris’-related strains differentiation corroborating the 16S rDNA designed subgroups. Several publically available sequences of the 3.6 kb phytoplasma fragments, containing cpn10, cpn60, amp and nadE genes allowed design of primers for specific amplification of 1,397 bp fragments containing phytoplasma cpn60 gene. Variability of amplified sequences was then studied in 27 ‘Ca. P. asteris’-related strains belonging to different 16SrI subgroups. The RFLP analyses of the amplified fragment with TruI and AluI restriction enzymes confirmed the reported differentiation among 16SrI-A, I-B, I-C, I-F and I-P subgroups, and showed further differentiation in strains assigned to 16SrI-A, 16SrI-B and 16SrI-C subgroups. However, analyses of cpn60 gene failed to discriminate strains in subgroups 16SrI-L and 16SrI-M (described on the basis of 16S rDNA interoperon heterogeneity) from strains in subgroup 16SrI-B, as it was also shown on tuf and rp genes. On the contrary, the 16SrI unclassified strain ca2006/5 from carrot (showing interoperon heterogeneity) was differentiable on both rp and cpn60 genes from the strains in subgroup 16SrI-B. These results indicate that interoperon sequence heterogeneity of strains AY2192, and PRIVA (16SrI-L), AVUT (16SrI-M), and ca2006/5 resulted in multigenic changes - one evolutionary step further - only in the latter case. Phylogenetic analyses carried out on full cpn60 gene (1,610 bp) are in agreement with 16Sr-based phylogeny, and confirmed also the further differentiation detected by RFLP analyses on specifically amplified and sequenced 1,397 bp fragments. Maximum sequence variability among the 16SrI group examined strains was 6.2% mismatches in cpn60 gene, while maximum reported sequence variability among the same phytoplasmas was 2.6% for 16S rDNA, 3.6% for tuf and 3.2% for rp genes
Figure 5 in An exceptional partial skeleton of a new basal raptor (Aves: Accipitridae) from the late Oligocene Namba formation, South Australia
No full textFigure 5. Proximal humerus fragments of Archaehierax sylvestris gen. et. sp. nov. SAMA P.54998: right, in caudal view (A); left, in dorsal (B) and cranial (C) views. Specimens in B and C are coated in ammonium chloride. Abbreviations: CD, crista deltopectoralis; CDF, crus dorsale fossae; CH, caput humeri; CVF, crus ventrale fossae; FP, fossa pneumotricipitalis; IC, incisura capitis; IH, intumescentia humeri; SLT, sulcus ligamenti transversus. Scale bars are 10 mm.Published as part of Mather, Ellen K., Lee, Michael S. Y., Camens, Aaron B. & Worthy, Trevor H., 2021, An exceptional partial skeleton of a new basal raptor (Aves: Accipitridae) from the late Oligocene Namba formation, South Australia, pp. 1175-1207 in Historical Biology 34 (7) on page 12, DOI: 10.1080/08912963.2021.1966777, http://zenodo.org/record/553448
An exceptional partial skeleton of a new basal raptor (Aves: Accipitridae) from the late Oligocene Namba formation, South Australia
No full textThe Australian pre-Pleistocene fossil record of Accipitridae (eagles, hawks, old-world vultures) comprises one latest Oligocene or early Miocene and one middle Miocene species, each represented by partial bones. Globally, most fossil accipitrids are based on single bones. The recent discovery of an older and considerably more complete accipitrid from late Oligocene sediments in Australia is therefore significant. It is derived from the Pinpa Local Fauna from the Namba Formation at Lake Pinpa, South Australia (~26–24 Ma). The fossil, described as Archaehierax sylvestris gen. et sp. nov., represents a raptor that was larger than the black-breasted buzzard Hamirostra melanosternon but smaller and more gracile than the wedge-tailed eagle Aquila audax. Comprehensive morphological and molecular phylogenetic analyses resolved Archaehierax as a basal accipitrid, not closely related to any living subfamily and perhaps the sister taxon to all other accipitrids exclusive of elanines. Relatively short wings similar to species of Spizaetus and Spilornis suggest it was adapted for flight within enclosed forests. Additional accipitrid fossils from the Namba Formation, a distal femur and a distal humerus, are incomparable with the holotype of A. sylvestris; they may represent distinct species or smaller individuals of the new taxon. lsid:zoobank.org:pub:6A25C569-3E9F-43B8-AAF8-F36CE405C06E</p
STM on polycrystalline thin films
No full textReiss G. STM on polycrystalline thin films. Vacuum. 1990;41(4-6):1322-1324.Examples for correlations of results of Scanning Tunnelling Microscopy (STM) with thickness dependent physical properties of thin films will be discussed: surface roughness enhances the thickness dependent resistivity. This effect can be described quantitatively by STM imaging. Good agreement with a simple model of the film resistivity can be found for Au and Cr-Au films. The magnetization loops of Au-Fe-Au films depend on the preparation parameters, although RHEED indicates identical flat surfaces. STM, however, often shows different local topographies. Again a direct correlation can be established
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