ABSTRACT
The initial molecular lesions through which viroids, satellite RNAs and viruses trigger signal cascades resulting in plant diseases are hotly debated. Since viroids are circular ...non-protein-coding RNAs of ∼250–430 nucleotides, they appear very convenient to address this issue. Viroids are targeted by their host RNA silencing defense, generating viroid-derived small RNAs (vd-sRNAs) that are presumed to direct Argonaute (AGO) proteins to inactivate messenger RNAs, thus initiating disease. Here, we review the existing evidence. Viroid-induced symptoms reveal a distinction. Those attributed to vd-sRNAs from potato spindle tuber viroid and members of the family Pospiviroidae (replicating in the nucleus) are late, non-specific and systemic. In contrast, those attributed to vd-sRNAs from peach latent mosaic viroid (PLMVd) and other members of the family Avsunviroidae (replicating in plastids) are early, specific and local. Remarkably, leaf sectors expressing different PLMVd-induced chloroses accumulate viroid variants with specific pathogenic determinants. Some vd-sRNAs containing such determinant guide AGO1-mediated cleavage of mRNAs that code for proteins regulating chloroplast biogenesis/development. Therefore, the initial lesions and the expected phenotypes are connected by short signal cascades, hence supporting a cause-effect relationship. Intriguingly, one virus satellite RNA initiates disease through a similar mechanism, whereas in the Pospiviroidae and in plant viruses the situation remains uncertain.
Comparison of symptoms and molecular pathways supports that viroids replicating in chloroplasts initiate disease (specific plant chloroses) by RNA silencing mRNAs encoding proteins involved in chloroplast biogenesis/development, while the situation is unclear for those replicating in nuclei (inducing non-specific alterations like stunting).
Summary
How viroids, tiny non‐protein‐coding RNAs (∼250–400 nt), incite disease is unclear. One hypothesis is that viroid‐derived small RNAs (vd‐sRNAs; 21–24 nt) resulting from the host defensive ...response, via RNA silencing, may target for cleavage cell mRNAs and trigger a signal cascade, eventually leading to symptoms. Peach latent mosaic viroid (PLMVd), a chloroplast‐replicating viroid, is particularly appropriate to tackle this question because it induces an albinism (peach calico, PC) strictly associated with variants containing a specific 12–14‐nt hairpin insertion. By dissecting albino and green leaf sectors of Prunus persica (peach) seedlings inoculated with PLMVd natural and artificial variants, and cloning their progeny, we have established that the hairpin insertion sequence is involved in PC. Furthermore, using deep sequencing, semi‐quantitative RT‐PCR and RNA ligase‐mediated rapid amplification of cDNA ends (RACE), we have determined that two PLMVd‐sRNAs containing the PC‐associated insertion (PC‐sRNA8a and PC‐sRNA8b) target for cleavage the mRNA encoding the chloroplastic heat‐shock protein 90 (cHSP90), thus implicating RNA silencing in the modulation of host gene expression by a viroid. Chloroplast malformations previously reported in PC‐expressing tissues are consistent with the downregulation of cHSP90, which participates in chloroplast biogenesis and plastid‐to‐nucleus signal transduction in Arabidopsis. Besides PC‐sRNA8a and PC‐sRNA8b, both deriving from the less‐abundant PLMVd (−) strand, we have identified other PLMVd‐sRNAs potentially targeting peach mRNAs. These results also suggest that sRNAs derived from other PLMVd regions may downregulate additional peach genes, ultimately resulting in other symptoms or in a more favorable host environment for viroid infection.
Mutation rates vary by orders of magnitude across biological systems, being higher for simpler genomes. The simplest known genomes correspond to viroids, subviral plant replicons constituted by ...circular non-coding RNAs of few hundred bases. Previous work has revealed an extremely high mutation rate for chrysanthemum chlorotic mottle viroid, a chloroplast-replicating viroid. However, whether this is a general feature of viroids remains unclear. Here, we have used high-fidelity ultra-deep sequencing to determine the mutation rate in a common host (eggplant) of two viroids, each representative of one family: the chloroplastic eggplant latent viroid (ELVd, Avsunviroidae) and the nuclear potato spindle tuber viroid (PSTVd, Pospiviroidae). This revealed higher mutation frequencies in ELVd than in PSTVd, as well as marked differences in the types of mutations produced. Rates of spontaneous mutation, quantified in vivo using the lethal mutation method, ranged from 1/1000 to 1/800 for ELVd and from 1/7000 to 1/3800 for PSTVd depending on sequencing run. These results suggest that extremely high mutability is a common feature of chloroplastic viroids, whereas the mutation rates of PSTVd and potentially other nuclear viroids appear significantly lower and closer to those of some RNA viruses.
El presente trabajo tuvo como objetivo principal determinar el nivel de calidad de servicio de transporte público en la ciudad del Cusco en el año 2018.
La investigación realizada corresponde al tipo ...básico, descriptivo y de corte transversal. El diseño es no-experimental, se determinaron dos muestras tanto por parte de la oferta y demanda, en la oferta se determinaron 41 empresas de transporte urbano y en la demanda se considera a los usuarios cuya muestra asciende a 384 usuarios de diferentes empresas de transporte, a quienes se aplicaron instrumentos de preguntas para conocer la percepción y opinión sobre la calidad del servicio. La técnica de investigación utilizada fue la recolección de datos a través de una encuesta estructurada aplicada a los conductores y propietarios de las empresas de transporte.
En la ciudad del Cusco las unidades de transporte recorren como mínimo 8 km y como ruta larga hasta 32 km concesionadas por la municipalidad provincial del Cusco. La población que demanda los servicios de transporte asciende a un total de 448,121 habitantes. Que se movilizan diariamente a sus centros de trabajo y estudio.
El uso del transporte diario de sexo masculino es de 54.5% y de sexo femenino es de 46.5%; el uso de personas adultas es de 41.8% que se movilizan diariamente a sus centros de labor y el 33.6% son jóvenes que se movilizan a sus centros de estudio, la diferencia lo realizan niños y personas de la tercera edad.
Despite being composed by a single-stranded, circular, non-protein-coding RNA of just 246–401 nucleotides (nt), viroids can incite in their host plants symptoms similar to those caused by DNA and RNA ...viruses, which have genomes at least 20-fold bigger and encode proteins. On the other hand, certain non-protein-coding plant satellite RNAs display structural similarities with viroids but for replication and transmission they need to parasitize specific helper viruses (modifying concomitantly the symptoms they induce). While phenotypic alterations accompanying infection by viruses may partly result from expressing the proteins they code for, how the non-protein-coding viroids (and satellite RNAs) cause disease remains a conundrum. Initial ideas on viroid pathogenesis focused on a direct interaction of the genomic RNA with host proteins resulting in their malfunction. With the advent of RNA silencing, it was alternatively proposed that symptoms could be produced by viroid-derived small RNAs (vd-sRNAs) —generated by the host defensive machinery— targeting specific host mRNA or DNA sequences for post-transcriptional or transcriptional gene silencing, respectively, a hypothesis that could also explain pathogenesis of non-protein-coding satellite RNAs. Evidence sustaining this view has been circumstantial, but recent data provide support for it in two cases: i) the yellow symptoms associated with a specific satellite RNA result from a 22-nt small RNA (derived from the 24-nt fragment of the satellite genome harboring the pathogenic determinant), which is complementary to a segment of the mRNA of the chlorophyll biosynthetic gene CHLI and targets it for cleavage by the RNA silencing machinery, and ii) two 21-nt vd-sRNAS containing the pathogenic determinant of the albino phenotype induced by a chloroplast-replicating viroid target for cleavage the mRNA coding for the chloroplastic heat-shock protein 90 via RNA silencing too. This evidence, which is compelling for the satellite RNA, does not exclude alternative mechanisms.
► Viroids might cause disease by interaction of their genomic RNA with host proteins. ► Instead, viroid-derived small RNAs could inactivate host RNA or DNA via RNA silencing.
Objective
The objective of this study was to develop and validate a risk scale (MARIACHI) for patients classified as non-ST-segment elevation acute coronary syndrome (NSTEACS) in a prehospital ...setting with the ability to identify patients at an increased risk of mortality at an early stage.
Methods
A retrospective observational study conducted in Catalonia over two periods: 2015–2017 (development and internal validation cohort) and Aug 2018–Jan 2019 (external validation cohort). We included patients classified as prehospital NSTEACS, assisted by an advanced life support unit and requiring hospital admission. The primary outcome was in-hospital mortality. Cohorts were compared using logistic regression and a predictive model was created using bootstrapping techniques.
Results
The development and internal validation cohort included 519 patients. The model is composed of five variables associated with hospital mortality: age, systolic blood pressure, heart rate > 95 bpm, Killip-Kimball III–IV and ST depression ≥ 0.5 mm. The model showed good overall performance (Brier = 0.043) and consistency in discrimination (AUC 0.88, 95% CI 0.83–0.92) and calibration (slope = 0.91; 95% CI 0.89–0.93). We included 1316 patients for the external validation sample. There was no difference in discrimination (AUC 0.83, 95% CI 0.78–0.87; DeLong Test
p
= 0.071), but there was in calibration (
p
< 0.001), so it was recalibrated. The finally model obtained was stratified and scored into three groups according to the predicted risk of patient in-hospital mortality: low risk: < 1% (-8 to 0 points), moderate risk: 1–5% (+ 1 to + 5 points) and high risk: > 5% (6–12 points).
Conclusion
The MARIACHI scale showed correct discrimination and calibration to predict high-risk NSTEACS. Identification of high-risk patients may help with treatment and low referral decisions at the prehospital level.
Viroids and viroid-like satellite RNAs from plants, and the human hepatitis delta virus (HDV) RNA share some properties that include small size, circularity and replication through a rolling-circle ...mechanism. Replication occurs in different cell compartments (nucleus, chloroplast and membrane-associated cytoplasmatic vesicles) and has three steps: RNA polymerization, cleavage and ligation. The first step generates oligomeric RNAs that result from the reiterative transcription of the circular templates of one or both polarities, and is catalyzed by either the RNA-dependent RNA polymerase of the helper virus on which viroid-like satellite RNAs are functionally dependent, or by host DNA-dependent RNA polymerases that, remarkably, viroids and HDV redirect to transcribe RNA templates. Cleavage is mediated by host enzymes in certain viroids and viroid-like satellite RNAs, while in others and in HDV is mediated by cis-acting ribozymes of three classes. Ligation appears to be catalyzed mainly by host enzymes. Replication most likely also involves many other non-catalytic proteins of host origin and, in HDV, the single virus-encoded protein.
The INK4/ARF locus encodes three tumour suppressors (p15INK4b, ARF and p16INK4a) and is among the most frequently inactivated loci in human cancer. However, little is known about the mechanisms that ...govern the expression of this locus. Here we have identified a putative DNA replication origin at the INK4/ARF locus that assembles a multiprotein complex containing Cdc6, Orc2 and MCMs, and that coincides with a conserved noncoding DNA element (regulatory domain RDINK4/ARF). Targeted and localized RNA-interference-induced heterochromatinization of RDINK4/ARF results in transcriptional repression of the locus, revealing that RDINK4/ARF is a relevant transcriptional regulatory element. Cdc6 is overexpressed in human cancers, where it might have roles in addition to DNA replication. We have found that high levels of Cdc6 result in RDINK4/ARF-dependent transcriptional repression, recruitment of histone deacetylases and heterochromatinization of the INK4/ARF locus, and a concomitant decrease in the expression of the three tumour suppressors encoded by this locus. This mechanism is reminiscent of the silencing of the mating-type HM loci in yeast by replication factors. Consistent with its ability to repress the INK4/ARF locus, Cdc6 has cellular immortalization activity and neoplastic transformation capacity in cooperation with oncogenic Ras. Furthermore, human lung carcinomas with high levels of Cdc6 are associated with low levels of p16INK4a. We conclude that aberrant expression of Cdc6 is oncogenic by directly repressing the INK4/ARF locus through the RDINK4/ARF element.
PALABRAS CLAVE paisaje; andenes; sostenibilidad; cambio climático; Andes; Perú SUMMARY The territorial anthropization of the habitat, at altitudes ranging from 2900 mamsl to 3800 mamsl, has created ...unique landscapes in the central Andes, Peru, such as those generated by the agricultural andenes in the district of Cabana in the Sondondo Valley (Lucanas, Ayacucho). ...these high landscapes with agricultural structures are damaged by lack of funding or institutional support to rural communities, as well as by climate impacts. Heterogeneous human interventions through sustainable uses of land, water and biodiversity at different Andean strata, tracing back to pre-Hispanic times, reflect the ancestral knowledge, practices and techniques of the Waris and the Incas. KEYWORDS landscape; andenes; sustainability; climate change; Andes, Peru EL DISTRITO DE CABANA Las andenerías y los bofedales de la altiplanicie de Cabana (figura 1), cuya comunidad forma parte del valle del Sondondo, Perú, están siendo recientemente propuestos como referentes para la inscripción de dicho valle como Patrimonio Mundial de la Humanidad, así como para promover la declaración de este valle como Paisaje Cultural Vivo1, a fin de que sea reconocido como Patrimonio Cultural de la Nación del Perú.
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