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PURPOSE: AUA guidelines for patients with microhematuria (≥3 red blood cells [RBC]/high-power field [hpf]) include cystoscopy for most over age 40 due to risk of urothelial cancer (UC). Cxbladder Triage (CxbT) is a urinary genomic test with UC negative predictive value of 99%. In this prospective randomized controlled trial, we compared cystoscopy use in a standard of care (SOC) arm vs a marker-based approach. MATERIALS AND METHODS: All patients with hematuria provided urine for a CxbT. Those categorized as lower risk (LR), defined as 3 to 29 RBC/hpf and minimal smoking history (<10 pack-years) were randomized between the test group provided with the CxbT result vs the SOC control group. Negative CxbT patients were offered omission of cystoscopy with surveillance. "Not lower risk" (NLR) patients (>30 RBC/hpf or >10 pack-year smoking history) had a CxbT but otherwise SOC. Patient decision and outcomes were recorded. RESULTS: Of 390 eligible patients, 255 were NLR and 135 were LR randomized to CxbT informed decision or SOC. The median age was 62 years (range 18-94) and 54% were male. Overall, 63% of CxbT tests were negative. For NLR patients, 82% had cystoscopy. In the LR control group, cystoscopy was performed in 67% of SOC and 27% in the test group (relative risk 0.41 [95% CI 0.27-0.61]). Compared to cystoscopy, CxbT had 90% sensitivity, 56% specificity, and 99% negative predictive value for UC. CONCLUSIONS: In this prospective randomized controlled trial, use of CxbT in patients with LR hematuria resulted in 59% reduction of cystoscopy use. This clinical utility of CxbT can reduce the burden of unnecessary cystoscopies.
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Cistoscopía , Hematuria , Triaje , Neoplasias de la Vejiga Urinaria , Humanos , Cistoscopía/efectos adversos , Masculino , Hematuria/diagnóstico , Hematuria/etiología , Femenino , Persona de Mediana Edad , Estudios Prospectivos , Anciano , Neoplasias de la Vejiga Urinaria/diagnóstico , Triaje/métodos , Medición de Riesgo/métodos , Adulto , Enfermedades AsintomáticasRESUMEN
PURPOSE: Microhematuria is a prevalent condition and the American Urological Association has developed a new risk-stratified approach for the evaluation of patients with microhematuria. Our objective was to provide the first evaluation of this important guideline. MATERIALS AND METHODS: This multinational cohort study combines contemporary patients from 5 clinical trials and 2 prospective registries who underwent urological evaluation for hematuria. Patients were stratified into American Urological Association risk strata (low, intermediate or high risk) based on sex, age, degree of hematuria, and smoking history. The primary end point was the incidence of bladder cancer within each risk stratum. RESULTS: A total of 15,779 patients were included in the analysis. Overall, 727 patients (4.6%) were classified as low risk, 1,863 patients (11.8%) were classified as intermediate risk, and 13,189 patients (83.6%) were classified as high risk. The predominance of high risk patients was consistent across all cohorts. A total of 857 bladder cancers were diagnosed with a bladder cancer incidence of 5.4%. Bladder cancer was more prevalent in men, smokers, older patients and patients with gross hematuria. The cancer incidence for low, intermediate and high risk groups was 0.4% (3 patients), 1.0% (18 patients) and 6.3% (836 patients), respectively. CONCLUSIONS: The new risk stratification system separates hematuria patients into clinically meaningful categories with differing likelihoods of bladder cancer that would justify evaluating the low, intermediate and high risk groups with incremental intensity. Furthermore, it provides the relative incidence of bladder cancer in each risk group which should facilitate patient counseling regarding the risks and benefits of evaluation for bladder cancer.
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Hematuria/clasificación , Hematuria/etiología , Neoplasias de la Vejiga Urinaria/complicaciones , Adulto , Anciano , Estudios de Cohortes , Femenino , Humanos , Incidencia , Masculino , Persona de Mediana Edad , Guías de Práctica Clínica como Asunto , Estudios Prospectivos , Medición de Riesgo , Sociedades Médicas , Estados Unidos , Neoplasias de la Vejiga Urinaria/epidemiología , UrologíaRESUMEN
BACKGROUND: Cxbladder diagnostic tests combine genomic information from urinary mRNA with phenotypic information to either rule out low-risk individuals or identify patients at a high risk of urothelial carcinoma (UC). OBJECTIVE: To evaluate the performance of Cxbladder and urine cytology, and Cxbladder's adjudication of atypical cytology and equivocal cystoscopy. DESIGN, SETTING, AND PARTICIPANTS: This is a retrospective analysis of pooled data from three prospective Cxbladder clinical trials and one real-world clinical study. Physicians were blinded to Cxbladder results, and Cxbladder providers were blinded to clinical results. This study analyzed diverse urology practices in the USA, Australia, and New Zealand. A total of 1784 consecutive, prospectively recruited patients with hematuria or previously diagnosed UC provided 852 samples with both local cytology and Cxbladder results; 153 had atypical cytologies and 14 had both atypical cytology and equivocal cystoscopy. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Negative predictive value (NPV) and proportion of tumors missed for Cxbladder and local cytology, and evaluation of Cxbladder for adjudicating atypical cytology and equivocal cystoscopy. RESULTS AND LIMITATIONS: Cxbladder ruled out 35% of patients and NPV 97% (95% confidence interval [CI] 94-98%) compared with 93% (95% CI 91-94%) for cytology; Cxbladder missed 8.5% and cytology missed 63% of tumors. UC was diagnosed in 26/153 cases of atypical cytology (17%). Cxbladder correctly adjudicated all these patients including those with both atypical cytology and equivocal cystoscopy; these patients had a positive Cxbladder result and were diagnosed with UC by pathology. The incidence of patients with both atypical cytology and equivocal cystoscopy is low. CONCLUSIONS: Cxbladder correctly adjudicated all patients diagnosed with UC among those with atypical cytology and equivocal cystoscopy, and outperformed cytology for accurately identifying patients who do not have UC. PATIENT SUMMARY: Cxbladder accurately rules out patients who do not have cancer, and adjudicates cytology and cystoscopy with inconclusive results, minimizing the need for patients to undergo further unnecessary tests and procedures.
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Adenocarcinoma/diagnóstico , Adenocarcinoma/patología , Neoplasias de la Vejiga Urinaria/diagnóstico , Neoplasias de la Vejiga Urinaria/patología , Adenocarcinoma/genética , Anciano , Anciano de 80 o más Años , Biomarcadores de Tumor/genética , Biomarcadores de Tumor/orina , Ensayos Clínicos como Asunto , Cistoscopía , Reacciones Falso Negativas , Femenino , Perfilación de la Expresión Génica , Humanos , Masculino , Persona de Mediana Edad , Valor Predictivo de las Pruebas , Estudios Retrospectivos , Vejiga Urinaria/patología , Neoplasias de la Vejiga Urinaria/genética , Orina/citologíaRESUMEN
BACKGROUND: The non-invasive Cxbladder urine test system has demonstrated clinical utility in ruling out urothelial carcinoma (UC) in patients with asymptomatic microscopic hematuria (AMH), suggesting that the number of invasive diagnostic tests, including cystoscopy, used in this patient population may be reduced by Cxbladder testing prior to conducting a full urological work-up. The aim of this study was to demonstrate the enhanced clinical utility of communicating objective information on diagnostic decisions made by individual physicians on individual patients with AMH. METHODS: Three hundred ninety-six physician-patient decisions were generated from twelve participant physicians evaluating real world case notes from the same 33 patients presenting with AMH. Each physician reviewed and recommended diagnostic tests and procedures based on each patient's referral data and then re-evaluated their clinical recommendation following disclosure of the non-invasive Cxbladder urine test result. Changes assessed were the total number of requested diagnostic procedures and the number of invasive procedures, including cystoscopy, following addition of information from Cxbladder in the Triage and Triage and Detect modalities. RESULTS: Physicians made significant changes to their diagnostic behavior for patients with AMH when presented with Cxbladder test results, including a reduction in the number of total and invasive procedures including cystoscopy for individuals identified as having a low probability of UC. The intensity of investigation was targeted and increased, including use of total procedures and cystoscopy, for patients identified by Cxbladder tests as having a high probability of UC: urologists increased the level of investigation for both total procedures and invasive procedures. The outcome resulted in patients with a high risk of UC receiving appropriate guideline-recommended invasive diagnostic tests. Patients who tested negative were offered fewer and significantly less invasive procedures. This change in physician behavior results in an increased clinical and patient utility, lower risk of missed UC and invasive test-related harm incidents. CONCLUSIONS: This study demonstrated the potential for increased clinical resolution and significantly enhanced patient management, when physicians consider Cxbladder test results in their clinical evaluation. The change in physician behavior led to more appropriate diagnostic procedure selection and resource allocation to the benefit of both patients and healthcare systems.
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Toma de Decisiones Clínicas/métodos , Hematuria/diagnóstico por imagen , Hematuria/orina , Relaciones Médico-Paciente , Estadística como Asunto/métodos , Pruebas Diagnósticas de Rutina/métodos , Hematuria/epidemiología , Humanos , Estudios Prospectivos , Medición de Riesgo , Urinálisis/métodosRESUMEN
INTRODUCTION: International guidelines advocate regular surveillance of patients following urothelial carcinoma (UC). A validated molecular diagnostic non-invasive urine test, Cxbladder Monitor, correctly identifies patients with a UC history who have low-probability of recurrence. The present study assesses the clinical utility of Cxbladder Monitor in reducing the number and frequency of urologic procedures ordered without missing detection of recurrent UC. METHODS: Data from 828 physician-patient assessments were generated from 18 participant physicians who each evaluated the same real-world clinical case data for 30 patients undergoing surveillance for recurrent UC. Each physician ordered tests and procedures and their timing, following review of the patient's demographic data, pre-existing conditions, risk factors and clinical history before and after disclosure of Cxbladder Monitor results. Changes in the number, type and timing of procedures ordered were assessed. RESULTS: The addition of Cxbladder Monitor significantly reduced the overall number of tests ordered by 38.7%, including flexible cystoscopy by 43%, for patients whose Cxbladder Monitor result was low-probability. When the result was elevated-probability, the number of procedures ordered, including cystoscopy, was increased consistent with the increased risk of recurrent UC. Importantly, based on the tests ordered by each physician for each of the patients, all cases of recurrent UC would have been detected. CONCLUSION: The increase in clinical utility of Cxbladder Monitor for the management of patients undergoing surveillance for recurrent UC was shown to be driven by the reduction in procedures ordered for low-probability patients and for the more invasive procedures ordered for elevated-probability patients. In this study, the total number of procedures ordered, including the number of cystoscopies, was reduced especially in patients with low-probability of UC. The invasive procedures were ordered in a more targeted fashion for elevated-probability patients, without compromising the detection of recurrent UC. CLINICALTRIALS. GOV IDENTIFIER: NCT02700659. FUNDING: Pacific Edge Limited.
RESUMEN
INTRODUCTION: This study aimed to demonstrate the clinical utility of non-invasive multigene Cxbladder urine tests in reducing the overall number of diagnostic tests and invasive procedures used in the clinical evaluation of patients presenting with microhematuria, a key symptom of urothelial carcinoma (UC). There is a belief that using non-invasive molecular diagnostic tests in patients with hematuria may lead to patients undergoing unnecessary and costly invasive procedures that can cause adverse events and decrease patient quality of life. The objective of this study was to determine whether or not this was the case, using Cxbladder. METHODS: Data from 396 patient-by-urologist interactions generated 792 decision points from a standardized cohort of 33 patients evaluated by 12 urologists. Participant physicians recommended a selection of tests and procedures based on referral data, then reviewed and amended their recommendations in the context of diagnostic information from Cxbladder used in the Triage and Triage and Detect clinical modalities. RESULTS: All urologists changed their diagnostic behavior in at least one patient case with the addition of Cxbladder results. The total number of diagnostic procedures was reduced by 5% and 25% following disclosure of results from Cxbladder in the Triage and the Triage and Detect modalities, respectively. The total number of requested invasive procedures was reduced from 425 at referral to 379 (-11%) and 292 (-31%) following disclosure of Cxbladder information in the Triage and Triage and Detect modalities, respectively. CONCLUSIONS: Urologists made compelling changes to their clinical decision-making when they were provided with Cxbladder results for patients presenting with hematuria. Cxbladder provides an increase in clinical utility by focusing the use of invasive diagnostic procedures to appropriate patients, reducing both the total number and number of invasive procedures used in the clinical management of patients with hematuria, thereby improving the diagnostic experience and outcomes for patients. FUNDING: Pacific Edge Ltd.
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Biomarcadores de Tumor/orina , Carcinoma/diagnóstico , Carcinoma/genética , Hematuria/diagnóstico , ARN/orina , Neoplasias Uretrales/diagnóstico , Neoplasias Uretrales/genética , Adulto , Anciano , Anciano de 80 o más Años , Estudios de Cohortes , Femenino , Humanos , Masculino , Persona de Mediana EdadRESUMEN
RNA binding proteins (RBPs) are integral components of ribonucleoprotein (RNP) complexes and play a central role in RNA processing. In plants, some RBPs function in a non-cell-autonomous manner. The angiosperm phloem translocation stream contains a unique population of RBPs, but little is known regarding the nature of the proteins and mRNA species that constitute phloem-mobile RNP complexes. Here, we identified and characterized a 50-kD pumpkin (Cucurbita maxima cv Big Max) phloem RNA binding protein (RBP50) that is evolutionarily related to animal polypyrimidine tract binding proteins. In situ hybridization studies indicated a high level of RBP50 transcripts in companion cells, while immunolocalization experiments detected RBP50 in both companion cells and sieve elements. A comparison of the levels of RBP50 present in vascular bundles and phloem sap indicated that this protein is highly enriched in the phloem sap. Heterografting experiments confirmed that RBP50 is translocated from source to sink tissues. Collectively, these findings established that RBP50 functions as a non-cell-autonomous RBP. Protein overlay, coimmunoprecipitation, and cross-linking experiments identified the phloem proteins and mRNA species that constitute RBP50-based RNP complexes. Gel mobility-shift assays demonstrated that specificity, with respect to the bound mRNA, is established by the polypyrimidine tract binding motifs within such transcripts. We present a model for RBP50-based RNP complexes within the pumpkin phloem translocation stream.
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Cucurbita/metabolismo , Floema/metabolismo , Proteínas de Plantas/metabolismo , Proteína de Unión al Tracto de Polipirimidina/metabolismo , Ribonucleoproteínas/metabolismo , Clonación Molecular , Cucurbita/genética , Datos de Secuencia Molecular , Proteínas de Plantas/genética , Proteína de Unión al Tracto de Polipirimidina/genética , ARN Mensajero/metabolismo , ARN de Planta/metabolismo , Ribonucleoproteínas/genéticaRESUMEN
Increasing evidence suggests that proteins present in the angiosperm sieve tube system play an important role in the long distance signaling system of plants. To identify the nature of these putatively non-cell-autonomous proteins, we adopted a large scale proteomics approach to analyze pumpkin phloem exudates. Phloem proteins were fractionated by fast protein liquid chromatography using both anion and cation exchange columns and then either in-solution or in-gel digested following further separation by SDS-PAGE. A total of 345 LC-MS/MS data sets were analyzed using a combination of Mascot and X!Tandem against the NCBI non-redundant green plant database and an extensive Cucurbit maxima expressed sequence tag database. In this analysis, 1,209 different consensi were obtained of which 1,121 could be annotated from GenBank and BLAST search analyses against three plant species, Arabidopsis thaliana, rice (Oryza sativa), and poplar (Populus trichocarpa). Gene ontology (GO) enrichment analyses identified sets of phloem proteins that function in RNA binding, mRNA translation, ubiquitin-mediated proteolysis, and macromolecular and vesicle trafficking. Our findings indicate that protein synthesis and turnover, processes that were thought to be absent in enucleate sieve elements, likely occur within the angiosperm phloem translocation stream. In addition, our GO analysis identified a set of phloem proteins that are associated with the GO term "embryonic development ending in seed dormancy"; this finding raises the intriguing question as to whether the phloem may exert some level of control over seed development. The universal significance of the phloem proteome was highlighted by conservation of the phloem proteome in species as diverse as monocots (rice), eudicots (Arabidopsis and pumpkin), and trees (poplar). These results are discussed from the perspective of the role played by the phloem proteome as an integral component of the whole plant communication system.
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Cucurbita/anatomía & histología , Cucurbita/metabolismo , Floema/química , Proteínas de Plantas/análisis , Proteoma/análisis , Proteínas de Arabidopsis/metabolismo , Secuencia Conservada , Cucurbita/genética , Genes de Plantas , Orgánulos/metabolismo , Exudados de Plantas/química , Proteínas de Plantas/química , Proteínas de Plantas/genética , Biosíntesis de Proteínas , Procesamiento Proteico-Postraduccional , Proteoma/química , Proteínas de Unión al ARN/metabolismo , Homología de Secuencia de Aminoácido , Especificidad de la Especie , Estrés Fisiológico , Ubiquitina/metabolismoRESUMEN
Cucurbita moschata, a cucurbit species responsive to inductive short-day (SD) photoperiods, and Zucchini yellow mosaic virus (ZYMV) were used to test whether long-distance movement of FLOWERING LOCUS T (FT) mRNA or FT is required for floral induction. Ectopic expression of FT by ZYMV was highly effective in mediating floral induction of long-day (LD)-treated plants. Moreover, the infection zone of ZYMV was far removed from floral meristems, suggesting that FT transcripts do not function as the florigenic signal in this system. Heterografting demonstrated efficient transmission of a florigenic signal from flowering Cucurbita maxima stocks to LD-grown C. moschata scions. Real-time RT-PCR performed on phloem sap collected from C. maxima stocks detected no FT transcripts, whereas mass spectrometry of phloem sap proteins revealed the presence of Cm-FTL1 and Cm-FTL2. Importantly, studies on LD- and SD-treated C. moschata plants established that Cmo-FTL1 and Cmo-FTL2 are regulated by photoperiod at the level of movement into the phloem and not by transcription. Finally, mass spectrometry of florally induced heterografted C. moschata scions revealed that C. maxima FT, but not FT mRNA, crossed the graft union in the phloem translocation stream. Collectively, these studies are consistent with FT functioning as a component of the florigenic signaling system in the cucurbits.
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Cucurbita/metabolismo , Proteínas de Plantas/metabolismo , Transducción de Señal , Secuencia de Aminoácidos , Arabidopsis/genética , Arabidopsis/metabolismo , Fraccionamiento Químico , Cucurbita/virología , Flores/fisiología , Regulación de la Expresión Génica de las Plantas , Vectores Genéticos , Meristema/citología , Datos de Secuencia Molecular , Péptidos/química , Floema/metabolismo , Fotoperiodo , Filogenia , Proteínas de Plantas/química , Proteínas de Plantas/genética , Virus de Plantas , Plantas Modificadas Genéticamente , ARN Mensajero/genética , ARN Mensajero/metabolismo , Homología de Secuencia de Aminoácido , Transcripción GenéticaRESUMEN
Cell-to-cell movement of potexviruses requires cognate recognition between the viral RNA, the triple gene block proteins (TGBp1-3) and the coat protein (CP). cis-acting motifs required for recognition and translocation of viral RNA were identified using an artificial potexvirus defective RNA encoding a green fluorescent protein (GFP) reporter transcriptionally fused to the terminal viral sequences. Analysis of GFP fluorescence produced in vivo from these defective RNA constructs, referred to as chimeric RNA reporters, was used to identify viral cis-acting motifs required for RNA trafficking. Mapping experiments localized the cis-acting element to nucleotides 1-107 of the Potato virus X (PVX) genome. This sequence forms an RNA secondary structural element that has also been implicated in viral plus-strand accumulation [Miller, E.D., Plante, C.A., Kim, K.-H., Brown, J.W. and Hemenway, C. (1998) J. Mol. Biol. 284, 591-608]. While replication and movement functions associated with this region have not been separated, these results are consistent with sequence-specific recognition of RNA by the viral movement protein(s). This situation is unusual among viral movement proteins that typically function to translocate RNA between cells in a non-sequence-specific manner. These data support the concept of cis-acting elements specifying intercellular potexvirus RNA movement and thus provide a basis for dissection of RNA-mediated intercellular communication in plants.
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Regiones no Traducidas 5'/metabolismo , Potexvirus/metabolismo , ARN Viral/metabolismo , Replicación Viral/fisiología , Plantas Modificadas Genéticamente , Nicotiana/citología , Nicotiana/virología , Proteínas Virales/genética , Proteínas Virales/metabolismoRESUMEN
Recent studies have revealed the operation of a long-distance communication network operating within the vascular system of higher plants. The evolutionary development of this network reflects the need to communicate environmental inputs, sensed by mature organs, to meristematic regions of the plant. One consequence of such a long-distance signaling system is that newly forming organs can develop properties optimized for the environment into which they will emerge, mature, and function. The phloem translocation stream of the angiosperms contains, in addition to photosynthate and other small molecules, a variety of macromolecules, including mRNA, small RNA, and proteins. This review highlights recent progress in the characterization of phloem-mediated transport of macromolecules as components of an integrated long-distance signaling network. Attention is focused on the role played by these proteins and RNA species in coordination of developmental programs and the plant's response to both environmental cues and pathogen challenge. Finally, the importance of developing phloem transcriptome and proteomic databases is discussed within the context of advances in plant systems biology.
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Floema/metabolismo , Transporte Biológico , Plantas/metabolismo , Plantas/virología , Transducción de SeñalRESUMEN
Two plasmids from the plant-pathogenic mollicute "Candidatus Phytoplasma australiense" were completely sequenced from two isolates derived from different plant hosts. Plasmid pPAPh2 (3607bp) was obtained from Phormium showing Phormium yellow leaf symptoms and pPASb11 (3635bp) from strawberry showing strawberry lethal yellows symptoms. The plasmids varied in their copy number and nucleotide sequence yet contained the same four open reading frames (ORFs). The deduced amino acid sequence derived from ORF1 shares similarity with hypothetical proteins encoded on the plasmids from onion yellows and beet leafhopper-transmitted virescence agent phytoplasmas. The deduced amino acid sequences of both ORF2 and ORF3 share similarity with functionally unknown proteins on the chromosome of onion yellows phytoplasma. An ORF with a similar sequence to ORF2 is also present on the chromosome of "Ca. P. australiense." The deduced amino acid sequence derived from ORF4 is most similar to replication proteins encoded by other phytoplasma plasmids and by geminiviruses, the only protein on the plasmids for which a putative function can be assigned. The identities of the deduced amino acid sequences of ORF1, ORF2, ORF3, and ORF4 between pPAPh2 and pPASb11 were 89, 68, 91, and 68%, respectively; the differences being consistent with the subgroup status of the parental phytoplasmas.
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Asparagaceae/microbiología , Fragaria/microbiología , Phytoplasma/genética , Enfermedades de las Plantas/genética , Plásmidos/genética , Secuencia de Aminoácidos , Secuencia de Bases , Mapeo Cromosómico , Cartilla de ADN , Datos de Secuencia Molecular , Análisis de Secuencia de ADNRESUMEN
Systemic translocation of RNA exerts non-cell-autonomous control over plant development and defense. Long-distance delivery of mRNA has been proven, but transport of small interfering RNA and microRNA remains to be demonstrated. Analyses performed on phloem sap collected from a range of plants identified populations of small RNA species. The dynamic nature of this population was reflected in its response to growth conditions and viral infection. The authenticity of these phloem small RNA molecules was confirmed by bioinformatic analysis; potential targets for a set of phloem small RNA species were identified. Heterografting studies, using spontaneously silencing coat protein (CP) plant lines, also established that transgene-derived siRNA move in the long-distance phloem and initiate CP gene silencing in the scion. Biochemical analysis of pumpkin (Cucurbita maxima) phloem sap led to the characterization of C. maxima Phloem SMALL RNA BINDING PROTEIN1 (CmPSRP1), a unique component of the protein machinery probably involved in small RNA trafficking. Equivalently sized small RNA binding proteins were detected in phloem sap from cucumber (Cucumis sativus) and lupin (Lupinus albus). PSRP1 binds selectively to 25-nucleotide single-stranded RNA species. Microinjection studies provided direct evidence that PSRP1 could mediate the cell-to-cell trafficking of 25-nucleotide single-stranded, but not double-stranded, RNA molecules. The potential role played by PSRP1 in long-distance transmission of silencing signals is discussed with respect to the pathways and mechanisms used by plants to exert systemic control over developmental and physiological processes.
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MicroARNs/metabolismo , ARN de Planta/metabolismo , ARN Interferente Pequeño/metabolismo , Transducción de Señal/fisiología , Secuencia de Aminoácidos , Arabidopsis/genética , Transporte Biológico/fisiología , Proteínas de la Cápside/genética , Cucumis sativus/citología , Cucumis sativus/genética , Cucumis sativus/fisiología , Cucurbita/citología , Cucurbita/genética , Cucurbita/fisiología , Silenciador del Gen , Genes de Plantas , Lupinus/citología , Lupinus/genética , Lupinus/fisiología , Datos de Secuencia Molecular , Plantas Modificadas Genéticamente , ARN de Planta/química , ARN de Planta/genéticaRESUMEN
Phloem-mobile endogenous RNA is trafficked selectively into the shoot apex. In contrast, most viruses and long-distance post-transcriptional gene silencing (PTGS) signals are excluded from the shoot apex. These observations suggest the operation of an underlying regulatory mechanism. To examine this possibility, a potexvirus movement protein, known to modify cell-to-cell trafficking and PTGS, was expressed ectopically in transgenic plants. These plants were found to be compromised in their capacity to exclude both viral RNA and silencing signals from the shoot apex. The transgenic plants also displayed various degrees of abnormal leaf polarity depending on transgene expression level. Normal patterns of organ development were restored by either virus- or Agrobacterium tumefaciens-mediated induction of PTGS. This revealed the presence of an RNA signal surveillance system that acts to allow the selective entry of RNA into the shoot apex. We propose that this surveillance system regulates signaling and protects the shoot apex, in particular the cells that give rise to reproductive structures, from viral invasion.