Modification of tobacco plant development by sense and antisense expression of the tomato viroid-induced AGC VIIIa protein kinase PKV suggests involvement in gibberellin signaling

<p>Abstract</p> <p>Background</p> <p>The serine-threonine protein kinase gene, designated <it>pkv </it>(protein kinase- viroid induced) was previously found to be transcriptionally activated in tomato plants infected with the plant pathogen <it>Potato spindle tuber viroid </it>(PSTVd). These plants exhibited symptoms of stunting, and abnormal development of leaf, root, and vascular tissues. The encoded protein, PKV, is a novel member of the AGC VIIIa group of signal-transducing protein kinases; however, the role of PKV in plant development is unknown. In this communication, we report the phenotypic results of over expression and silencing of <it>pkv </it>in transgenic tobacco.</p> <p>Results</p> <p>Over expression of <it>pkv </it>in <it>Nicotiana tabacum </it>cv. Xanthi (tobacco) resulted in stunting, reduced root formation, and delay in flowering, phenotypes similar to symptoms of PSTVd infection of tomato. In addition, homozygous T2 tobacco plants over expressing PKV were male sterile. Antisense expression of <it>pkv</it>, on the other hand, resulted in plants that were taller than non-transformed plants, produced an increased number of flowers, and were fertile. Exogenous application of GA₃stimulated stem elongation in the stunted, sense-expressing plants. PKV sense and antisense expression altered transcript levels of GA biosynthetic genes and genes involved in developmental and signaling pathways, but not genes involved in salicylic acid- or jasmonic acid-dependent pathways. Our data provide evidence suggesting that PKV plays an important role in a GA signaling pathway that controls plant height and fertility.</p> <p>Conclusion</p> <p>We have found that the over expression of the tomato protein kinase PKV resulted in stunting, modified vascular tissue development, reduced root formation, and male sterility in tobacco, and we propose that PKV regulates plant development by functioning in critical signaling pathways involved in gibberellic acid metabolism.</p

Molecular biology of viroid–host interactions and disease control strategies

AbstractViroids are single-stranded, covalently closed, circular, highly structured noncoding RNAs that cause disease in several economically important crop plants. They replicate autonomously and move systemically in host plants with the aid of the host machinery. In addition to symptomatic infections, viroids also cause latent infections where there is no visual evidence of infection in the host; however, transfer to a susceptible host can result in devastating disease. While there are non-hosts for viroids, no naturally occurring durable resistance has been observed in most host species. Current effective control methods for viroid diseases include detection and eradication, and cultural controls. In addition, heat or cold therapy combined with meristem tip culture has been shown to be effective for elimination of viroids for some viroid–host combinations. An understanding of viroid–host interactions, host susceptibility, and non-host resistance could provide guidance for the design of viroid-resistant plants. Efforts to engineer viroid resistance into host species have been underway for several years, and include the use of antisense RNA, antisense RNA plus ribozymes, a dsRNase, and siRNAs, among others. The results of those efforts and the challenges associated with creating viroid resistant plants are summarized in this review

Newly Discovered Natural Hosts of Tomato chlorosis virus in Costa Rica

Tomato chlorosis virus (ToCV) is an emerging whitefly-transmitted crinivirus. In Costa Rica in 2007, ToCV was detected in field-grown and greenhouse tomato (Solanum lycopersicum L.) plants causing symptoms of severe yellowing and foliar chlorosis.UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Biología Celular y Molecular (CIBCM

Psychosocial impact of undergoing prostate cancer screening for men with BRCA1 or BRCA2 mutations.

OBJECTIVES: To report the baseline results of a longitudinal psychosocial study that forms part of the IMPACT study, a multi-national investigation of targeted prostate cancer (PCa) screening among men with a known pathogenic germline mutation in the BRCA1 or BRCA2 genes. PARTICPANTS AND METHODS: Men enrolled in the IMPACT study were invited to complete a questionnaire at collaborating sites prior to each annual screening visit. The questionnaire included sociodemographic characteristics and the following measures: the Hospital Anxiety and Depression Scale (HADS), Impact of Event Scale (IES), 36-item short-form health survey (SF-36), Memorial Anxiety Scale for Prostate Cancer, Cancer Worry Scale-Revised, risk perception and knowledge. The results of the baseline questionnaire are presented. RESULTS: A total of 432 men completed questionnaires: 98 and 160 had mutations in BRCA1 and BRCA2 genes, respectively, and 174 were controls (familial mutation negative). Participants' perception of PCa risk was influenced by genetic status. Knowledge levels were high and unrelated to genetic status. Mean scores for the HADS and SF-36 were within reported general population norms and mean IES scores were within normal range. IES mean intrusion and avoidance scores were significantly higher in BRCA1/BRCA2 carriers than in controls and were higher in men with increased PCa risk perception. At the multivariate level, risk perception contributed more significantly to variance in IES scores than genetic status. CONCLUSION: This is the first study to report the psychosocial profile of men with BRCA1/BRCA2 mutations undergoing PCa screening. No clinically concerning levels of general or cancer-specific distress or poor quality of life were detected in the cohort as a whole. A small subset of participants reported higher levels of distress, suggesting the need for healthcare professionals offering PCa screening to identify these risk factors and offer additional information and support to men seeking PCa screening

Expression and functional characterization of the plant antimicrobial snakin-1 and defensin recombinant proteins

In this study, for the first time, functionally active, recombinant, cysteine-rich plant proteins snakin-1 (SN1) and defensin (PTH1) were expressed and purified using a prokaryotic expression system. The overall level of antimicrobial activities of SN1 and PTH1 produced in Escherichia coli was commensurate with that of the same proteins previously obtained from plant tissues. Both proteins exhibited strong antibacterial activity against the phytopathogenic bacterium Clavibacter michiganensis subsp. sepedonicus (50% inhibitory concentration (IC50) 1.5–8 lM) and antifungal activity against the phytopathogenic fungi Colletotrichum coccoides and Botrytis cinerea (IC50 5–14 lM). Significantly weaker activity was observed against Pseudomonas syringae pv. syringae and Pseudomonas syringae pv. tabaci. A pronounced synergistic antimicrobial effect against P. syringae pv. syringae and an additive effect against P. syringae pv. tabaci occurred with a combination of SN1 and PTH1. Aggregation of C. michiganensis subsp. sepedonicus bacterial cells at all protein concentrations tested was observed with the combination of SN1 and PTH1 and with SN1 alone. Our results demonstrate the use of a cost effective prokaryotic expression system for generation and in vitro characterization of plant cysteine-rich proteins with potential antimicrobial activities against a wide range of phytopathogenic microorganisms in order to select the most effective agents for future in vivo studies

Viroid Pathogenicity: One Process, Many Faces

Despite the non-coding nature of their small RNA genomes, the visible symptoms of viroid infection resemble those associated with many plant virus diseases. Recent evidence indicates that viroid-derived small RNAs acting through host RNA silencing pathways play a key role in viroid pathogenicity. Host responses to viroid infection are complex, involving signaling cascades containing host-encoded protein kinases and crosstalk between hormonal and defense-signaling pathways. Studies of viroid-host interaction in the context of entire biochemical or developmental pathways are just beginning, and many working hypotheses have yet to be critically tested

Occurrence of citrus viroids in Costa Rica

A survey for citrus viroids was conducted in The major citrus commercial growing areas in Costa Rica. Screening of 36 sweet orange and 12 lemon trees resulted in the detection of members of four of the five citrus viroid groups as detemined by nucleic acid hybridization using specific RNA probes and polymerase chain reaction (PCR) using specific oligonucleotide primers. CEVd, CVd-IIa, CVd-III and CVd-IH viroids were found to be widespread in the three main regions of commercial citurs production. CVd-Ib was only found in lemon in Nicoya.Se realizó un estudio sobre los viroides que infectan los cítricos en las principales regiones de Costa Rica donde se siembran comercialmente estos frutales. Se analizaron 36 muestras de árboles de naranja dulce y 12 de limón mediante las técnicas de hibridación de ácidos nucleicos con sondas ARN específicas y de la reacción en cadena de la polimerasa (PCR) usando imprimadores específicos. Se detectaron viroides pertenecientes a cuatro de los cinco grupos de viroides conocidos en el mundo. Los viroides CEVd, CVd-Ila, CVD-IIb y CVd-IIIb se encontraron ampliamente distribuidos en las tres regiones principales de producción comercial de cítricos del país. CVd-Ib se encontró solamente en limón en Nicoya.International Atomic Energy Agency///Universidad de Costa Rica/[801-94-905]/UCR/Costa Ric

First Report of Potato Spindle Tuber Viroid in Costa Rica

Datos y artículo incluido por Lisela Moreira Carmona, responsable de depósitos de publicaciones del área de Patógenos y Plagas del CIBCMDuring 1997 to 1998, symptoms of leaf roll, dwarfism, chlorosis, and occasional leaf necrosis were observed on Solanum tuberosum in several plots in Cartago, the principal potato-production region of Costa Rica. Because of the known association between potato leafroll virus (PLRV) and viroids (1) and previous reports of PLRV in Costa Rica, the presence of potato spindle tuber viroid (PSTVd) was suspected. Leaf samples from 122 symptomatic potato plants, cvs. Atzimba, Floresta, Idiafrit, and Birris, were collected from 10 plots. Total nucleic acids (TNAs) were extracted and purified (2) from collected symptomatic samples and six healthy potato controls. TNAs were spotted on nylon membranes and hybridized to a digoxigenin labeled DNA probe specific for PSTVd. Of 122 symptomatic plants, 71 were positive for PSTVd based on dot blot hybridization. TNAs from 12 positive potato samples, including at least 1 sample from each cultivar, were used to inoculate Lycopersicum esculentum cv. Super Marmande. Eleven of twelve inoculated tomato plants showed symptoms of dwarfism, leaf deformation, and grayish foliage, often with a dull surface. TNAs were extracted from inoculated tomato and hybridized to the PSTVd probe. All inoculated symptomatic plants were positive for PSTVd based on dot blot hybridization. This is the first report of PSTVd in Costa Rica.Universidad de Costa Rica/[801-94-905]/UCR/Costa RicaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Biología Celular y Molecular (CIBCM