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At least 703 records · Page 39Linked to original sources
PubMed2000

Graft transmission of post-transcriptional gene silencing: target specificity for RNA degradation is transmissible between silenced and non-silenced plants, but not between silenced plants.

Using the grafting procedure, we examined the transmission of post-transcriptional gene silencing (PTGS) in Nicotiana benthamiana which had been transformed with the coat protein gene, including the 3' non-translated region of the sweet potato feathery mottle potyvirus. Transmission of PTGS from silenced lines to non-silenced ones was bidirectional, but occurred efficiently from root stocks to scions. The level of transgene methylation in non-silenced scions grafted onto silenced root stocks was not increased. When grafted scions which had become silenced were removed from silenced root stocks and regrafted onto non-silenced or vector-transformed root stocks, PTGS was maintained. However, their progeny did not show PTGS. Previously we reported that our transgenic lines had different target specificities of PTGS for RNA degradation: one line recognized only the 3' part of the transgene mRNA while others involved the whole transgene mRNA (Sonoda et al. 1999, Phytopathology, 89, 385-391). Using these lines, we showed that target specificity of PTGS induced in non-silenced scions after grafting was determined by that in silenced root stocks. However, unexpectedly, target specificity of PTGS induced in silenced scions was not changed [corrected] by grafting onto silenced root stocks showing different target specificity, indicating that the second PTGS from silenced root stocks was not superimposed to silenced scions.

Gene Silencing↗
PubMed1988

Isolation and characterization of monoclonal antibodies directed against plant plasma membrane and cell wall epitopes: identification of a monoclonal antibody that recognizes extensin and analysis of the process of epitope biosynthesis in plant tissues and cell cultures.

Membranes from tobacco cell suspension cultures were used as antigens for the preparation of monoclonal antibodies. Use of solid phase and indirect immunofluorescence assays led to the identification of hybridomas producing antibodies directed against cell surface epitopes. One of these monoclonal antibodies (11.D2) was found to recognize a molecular species which on two-dimensional analysis (using nonequilibrium pH-gradient electrophoresis and SDS-PAGE) was found to have a high and polydisperse molecular mass and a very basic isoelectric point. This component was conspicuously labeled by [3H]proline in vivo. The monoclonal antibody cross-reacted with authentic tomato extensin, but not with potato lectin nor larch arabinogalactan. Use of the monoclonal antibody as an immunoaffinity reagent allowed the purification of a tobacco glycoprotein which was identical in amino acid composition to extensin. Finally, immunocytological analyses revealed tissue-specific patterns of labeling by the monoclonal antibody that were identical to those observed with a polyclonal antibody raised against purified extensin. We have concluded that monoclonal antibody 11.D2 recognizes an epitope that is carried exclusively by extensin. Analysis of cellular homogenates through differential and isopycnic gradient centrifugation revealed that biosynthesis of the extensin epitope was found on or within the membranes of the endoplasmic reticulum, Golgi region and plasma membrane. This result is consistent with the progressive glycosylation of the newly-synthesized extensin polypeptide during its passage through a typical eukaryotic endomembrane pathway of secretion. The 11.D2 epitope was not found in protoplasts freshly isolated from leaf tissues. However, on incubation of these protoplasts in appropriate culture media, biosynthesis of the epitope was initiated. This process was not impeded by the presence of chemicals that are reported to be inhibitors of cell wall production or of proline hydroxylation.

Antibodies, Monoclonal↗