Early stages in cell wall regeneration of tobacco mesophyll protoplasts : An electrophoretic study

The electrophoretic mobilities of isolated mesophyll protoplasts of Nicotiana tabacum var. Xanthi n.c. were measured using a whole cell electrophoresis apparatus. Changes in mobility were recorded at times during aseptic culture which related to events in the known sequence of de novo cell wall regeneration. It is proposed that these changes are a result of activity in, or at, the plasmalemma resulting in synthesis and transport to the cell surface of regenerated cell wall material. Coumarin, a compound known to affect the developmental sequence of cultured mesophyll protoplasts, was examined as a medium component during the regenerative process, differences in protoplast mobility resulting from Coumarin addition were recorded. The possible mode of action of Coumarin is discussedPeer reviewe

Similarities in the soluble protein profiles of leaf tissue following either a hypersensitive reaction to virus infection or plasmolysis

Cucumber cotyledons and cowpea leaves both react hypersensitively to tobacco necrosis virus (TNV) infection. The soluble fractions of these tissues, following virus-elicited necrosis, contained apparently novel proteins. The proteins from the two plant species are dissimilar regarding both molecular weight and chemical nature. The α and β fractions in cowpea are strictly proteinaceous, whilst the γ protein in cucumber, is a glycoprotein. Similar alterations to the soluble proteins in either plant type could be induced following a period of plasmolysis in mannitol at hypertonic concentration (0.5 M). Protoplasts isolated from both cucumber and cowpea tissue, plasmolysed as above, did not contain the induced protein fractions. Thus the proteins may be bound to the cell-wall, plasmalemma or present in the cellular free space. Similarities between the stress situation of plasmolysis or a hypersensitive reaction are discussed with a view to establishing the signal(s) for the synthesis or generation of the proteins, and their role and function in these plants, if any.Peer reviewe

Improved isolation and culture methods for cucumber mesophyll protoplasts

Improved methods for the isolation of large numbers of viable protoplasts from cotyledons and first leaves of two cultivars of cucumber, Cucumis sativus L. cv. Ashley and China are described. Short-term isolation methods (STM), and long-term isolation methods (LTM), using a variety of commercial enzymes are outlined. Liquid culture and subsequent solid culture of isolated first leaf protoplasts resulted in sustained cell division and eventual compact callus formation, which has been induced to form roots. No shoot or whole plant regeneration has, as yet, been demonstratedPeer reviewe

Alterations in RNA and protein metabolism in uninoculated half-leaves of cowpea adjacent to tobacco necrosis virus infected halves

Following inoculation of half-leaves of cowpea with tobacco necrosis virus (TNV, R 1 : 1.5 19 : S S : S Fu), two major protein fractions, termed α and β appear in soluble extracts, which are absent from sham-inoculated (control) tissue. The origin and role of these proteins are unknown, but they appear coincidently with hypersensitivity 3 days after inoculation. The same proteins appear 3 days later in apparently healthy tissue directly adjacent to necrotic half-leaves. Virus is absent from the apparently healthy tissue. During this time-course the ratios of the amounts of radiolabelled precursors incorporated into both total RNA and protein, between apparently healthy and healthy tissue were compared. No significant alterations in either were seen. However, alterations in 'early' polyadenylate (poly(A)) mRNA were observed reproducibly. Increases in 'early' mRNA up until 1 day postinfection of the adjacent half-leaf are not thought to be concerned with the synthesis of either the α or β fractions as these appear much later in apparently healthy tissue. Novel synthesis of the α and β fractions has not been demonstrated. The role of host-adaptation either by the amplification of small proteins or the degradation of larger proteins to produce the α and β fractions is discussed.Peer reviewe

Cassava latent virus specific DNAs in mosaic diseased cassava of Nigerian origin

Het genoom van het 'cassava latent' virus (CLV), een geminivirus, bestaat uit twee cirkelvormige, enkelstrengige DNA-moleculen nl. DNA 1 (2,78 kb) en DNA 2 (2,72 kb). DNA, verkregen uit Nicotiana benthamiana-planten, die mechanisch waren geïnoculeerd met sap van natuurlijk geïnfecteerde cassaveplanten, bevat naast het enkelstrengige genoom-DNA en de corresponderende open, lineaire en via covalent-bindingen gesloten cirkelvormige, extra-getwiste, dubbelstrengige vormen, een enkelstrengig DNA, dat kleiner is dan het genoom-DNA (c. 1,3 kb). Van dit DNA is aangetoond, dat het fungeert als een defect DNA. Het kleinere DNA interfereert met de functies van het genoom-DNA waardoor de plant minder hevige ziektebeelden gaat vertonen. Het was echter nog niet bekend of dezelfde DNA-vormen in het veld voorkomen in natuurlijk geïnfecteerde cassaveplanten met mozaïeksymptomen. In het hier beschreven onderzoek is aangetoond, dat de DNA-vormen in natuurlijk geïnfecteerde cassaveplanten overeenkomen met die in kunstmatig met het CLV geïnfecteerde N. benthamiana-planten. De hoeveelheid DNA, kleiner dan het genoom, wordt echter sterk verhoogd door passage van het virus van cassave naar N. benthamiana. De mogelijkheid, dat de hoeveelheid van het DNA, kleiner dan het genoom, in mozaïek-vertonende cassaveplanten gecorreleerd is met de mate van symptoomexpressie wordt besproken.Peer reviewe

Potato yellow mosaic geminivirus AC2 protein is a sequence non-specific DNA binding protein

The AC2 protein of potato yellow mosaic geminivirus (PYMV) is by analogy with related geminiviruses thought to be a transcriptional activator protein. We have over-expressed the AC2 open reading frame in E. coli and purified the protein from bacterial extracts to near homogeneity. We have studied the interaction of the AC2 protein with DNA and from gel retardation assays shown that it binds both double-stranded (ds) and single-stranded (ss) DNA non-specifically. The binding to PYMV intergenic region ds DNA appeared to be independent of the presence of zinc ions and did not require the protein to be phosphorylated.Peer reviewe

Expression and clinical significance of concomitant fak/src and p-paxillin in mobile tongue squamous cell carcinoma

Background/Aim: The focal adhesion kinase (FAK)/SRC phosphorylation cascade and its downstream target paxillin have been implicated in malignant transformation, tumor growth and progression, together with metastasis. The present study aimed to evaluate the clinical significance of concomitant FAK/SRC and p-paxillin expression in mobile tongue squamous cell carcinoma (SCC). Materials and Methods: FAK, SRC and phosphopaxillin expression in 48 mobile tongue SCC tissue samples was assessed immunohistochemically and analyzed with respect to clinicopathological characteristics and patient survival. Results: Concomitant high FAK/SRC expression was significantly associated with high grade of tumor differentiation (p=0.048) and longer disease-free patient survival (log-rank test, p=0.019). High p-paxillin expression was significantly associated with greater depth of invasion (p=0.002), lymph node metastasis (p=0.048) and poorer disease-free patient survival (log-rank test, p=0.021; Coxregression analysis, p=0.031). Conclusion: The present study provides evidence that FAK/SRC and paxillin play a role in the pathophysiological aspects of mobile tongue SCC and could constitute therapeutic targets

Closteroviridae

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