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J Gressel

Publications and source records attributed to J Gressel.

At least 37 records · Page 2Linked to original sources
PubMed1984

Benzyl viologen-mediated counteraction of diquat and paraquat phytotoxicities.

There was reason from bacterial and algal systems to expect that pretreatments with a paraquat analog might confer tolerance against a subsequent paraquat treatment. Thus, a series of compounds were tested for protective activity against bipyridinium herbicides. These included other bipyridinium compounds and derivatives, as well as compounds having similar or more positive redox potentials than paraquat and compounds known to increase or maintain high superoxide dismutase activity levels in plants.Only treatments with benzyl viologen, a benzyl analog of paraquat, protected Spirodela oligorrhiza (Kurz) Hegelm. colonies from otherwise damaging levels of diquat.NADP photoreduction by isolated thylakoids was inhibited by the same concentrations of paraquat, diquat, and benzyl viologen given separately. Thus, the benzyl viologen-mediated tolerance against the bipyridinium herbicides is probably not due to a direct interaction at the thylakoid level.Superoxide dismutase activity was about 50% higher in broken plastids of benzyl viologen-treated plants compared to controls, which may partly explain the observed tolerance.

Journal Article↗
PubMed1983

The determination of chlorophylls a and b together with 14CO2 fixation in the same plant tissue samples.

A simple, efficient, and inexpensive method for measuring radioactivity as well as chlorophylls a and b in a large number of plant tissue samples is presented. Chlorophyll is determined following extraction with dimethyl sulfoxide or N-N'-dimethylformamide. The solvent is then evaporated on glass-fiber filters and bleached under light. The filter disks are counted together with the cleared plant material.

Carbon Dioxide↗
PubMed1983

Elevated riboflavin requirement for postphotoinductive events in sporulation of a trichoderma auxotroph.

A riboflavin auxotroph of Trichoderma required more riboflavin for blue-light-induced conidiation than for growth. Colonies transferred after illumination from 0.2 micromolar (limiting conidiation, not growth) to 3.5 micromolar riboflavin (nonlimiting), responded the same as those grown at 3.5 micromolar. The additional riboflavin is therefore not required as a photoreceptor. The data do not rule out the hypothesis that cryptochrome(s) is/are flavin(s).

Journal Article↗
PubMed1983

Fungal biodegradation and biotransformation of soluble lignocarbohydrate complexes from straw.

Aspergillus japonicus is an efficient degrader of phenolics and carbohydrates present in a mixture of soluble lignocarbohydrate complexes extracted from wheat straw. Trichoderma sp. attacked part of the carbohydrate but hardly affected the aromatic portion of this solution. Polyporus versicolor had a complex effect; polymerization of low-molecular-size phenolics accompanied the degradation of aromatic and carbohydrate polymers. The addition of xylose to the medium facilitated depolymerization of lignin by the fungi tested and prevented the polymerization of low-molecular-size fractions of lignocarbohydrate complexes by P. versicolor. P. versicolor, in contrast to A. japonicus and Trichoderma sp., also excreted into the medium considerable amounts of laccase, but only in the absence of endogenous or exogenous carbohydrates. Apparently, laccase is involved in polymerization rather than degradation of lignin in this organism. A number of extracellular glycanases were also secreted by these fungi.

Journal Article↗
PubMed1979

Characterization of the 32,000 Dalton Chloroplast Membrane Protein: III. Probing Its Biological Function in Spirodela.

The rapidly turning over, photoinduced thylakoid protein, P-32000, is the main pulse-labeled membrane polypeptide in the chloroplasts of Spirodela oligorrhiza, yet little is known of its physiological function. Two hypotheses are tested: that P-32000 synthesis is necessary for thylakoid biogenesis; that it directly participates in photosynthesis. Spirodela cultures were dissected into expanding and fully mature tissue. Fronds from both developmental stages transcribed a 0.5 x 10(6) dalton RNA likely to be the message for P-32000. As to the protein itself, synthesis occurred in both types of tissue but was considerably enhanced in the fully mature state. Thus, a purely transient, developmental function for P-32000 during thylakoid biogenesis appears ruled out. Low concentrations of d-threo-chloramphenicol severely suppressed P-32000 synthesis but not its turnover. As a result, fronds depleted in P-32000 were obtained. However, photoassimilation of CO(2) remained at 86% of normal in tissue > 80% depleted of P-32000. Thus, P-32000 did not appear to be rate-limiting, suggesting that it does not serve as a direct, integral part of the photosynthetic pathway.

Journal Article↗
PubMed1977

Discoordination of ribosomal RNA metabolism during metabolic shifts of Spirodela plants.

The effects of metabolic shifts on nucleic acid syntheses have been widely studied in prokaryotes, but not in plants because of a paucity of suitable systems. Spirodela (Duckweed) was thus used to ascertain the response of the nucleocytoplasmic (nc) and plastid ribosomal RNA metabolisms to partial and total carbon deprivation. The 0.56 X 10(6) Mr plastid rRNA is the one species of RNA most affected by metabolic shifts; unlike other species, its appearance is delayed by deprivation and it appears more rapidly than other species on transfer from dark to light. The data suggest a discoordination between the transcription and processing of plastid ribosomal precursors. Incorporation into all nc and plastid rRNAs was severely reduced and all rRNA precursors accumulated in green plants that were completely deprived of carbon by transferring to the dark, without sucrose. The amounts of nc and plastid precursors transcribed readjusted to the reduced amounts processed to mature RNA only after long periods in the dark with sucrose. This delay involved the formation of new colorless plants. Less plastid RNAs, compared to nc RNAs are found in the dark steady state.

Chloroplasts↗
PubMed1975

Dinoflagellate ribosomal RNA; an evolutionary relic?

The apparent molecular weights of the rRNA subunits of the dinoflagellate Peridinium cinctum fa. westii were determined by polyacrylamide gel electrophoresis to obtain an indication of its evolutionary status. The apparent molecular weights of the Peridinium light and heavy rRNA subunits were 0.7 and 1.23 X 10(6) respectively. The light rRNA is therefore typically eukaryotic but the heavy rRNA has a significantly lower MW than previously reported for higher eukaryotes which range from 1.3 to 1.75 X 10(6) depending on their evolutionary position. Thus by this criterion Peridinium is similar to red algae and may represent a eukaryotic stage, lower than fungi or green plants.

Biological Evolution↗