Expression of a Zeatin-O-Glucoside-Degrading [beta]-Glucosidase in Brassica napusFalk, A.; Rask, L.
doi: 10.1104/pp.108.4.1369pmid: 7659745
Abstract A [beta]-glucosidase was purified from seeds of Brassica napus L. (oilseed rape). The 130-kD native enzyme consisted of a disulfide-linked dimer of 64-kD monomers. Internal amino acid sequences were used to construct degenerate primers for polymerase chain reaction-mediated cloning of cDNA for the enzyme. One nearly full-length and one partial [beta]-glucosidase-encoding cDNA clone were isolated and sequenced. Southern hybridization showed that [beta]-glucosidase is encoded by a small gene family in B. napus. Northern hybridization showed that the genes are expressed in the seed, with a low degree of expression in other tissues. In the seed, the expression started at 30 days after pollination (DAP), with the highest expression at 40 DAP. The size of the transcript was approximately 1900 nucleotides. In situ hybridization to developing seeds of B. napus showed that the [beta]-glucosidase expression started at 30 DAP around the provascular tissue in the embryo axis. In the cotyledons, mRNA initially accumulated around the provascular tissues but was detected first at 35 DAP. At 40 DAP, expression occurred in most parts of the seed. In situ hybridization also detected [beta]-glucosidase mRNA in shoots, young roots, and the basal part of the hypocotyls. Zeatin-O-glucoside was identified as a natural substrate for B. napus [beta]-glucosidase. This content is only available as a PDF. Copyright © 1995 by American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)
Systemic Responses in Arabidopsis thaliana Infected and Challenged with Pseudomonas syringae pv syringaeSummermatter, K.; Sticher, L.; Metraux, J. P.
doi: 10.1104/pp.108.4.1379pmid: 12228548
Abstract Attack of plants by necrotizing pathogens leads to acquired resistance to the same or other pathogens in tissues adjacent to or remotely located from the site of initial attack. We have used Arabidopsis thaliana inoculated with the incompatible pathogen Pseudomonas syringae pv syringae on the lower leaves to test the induction of systemic reactions. When plants were challenged with Pseudomonas syringae pv syringae in the upper leaves, bacterial titers remained stable in those preinfected on the lower leaves. However, there was a distinct decrease in symptoms that correlated with a local and systemic increase in salicylic acid (SA) and in chitinase activity. Peroxidase activity only increased at the site of infection. No changes in catalase activity were observed, either at the local or at the systemic level. No inhibition of catalase could be detected in tissue in which the endogenous levels of SA were elevated either naturally (after infection) or artificially (after feeding SA to the roots). The activity of catalase in homogenates of A. thaliana leaves could not be inhibited in vitro by SA. SA accumulation was induced by H2O2 in leaves, suggesting a link between H2O2 from the oxidative burst commonly observed during the hypersensitive reaction and the induction of a putative signaling molecule leading to system acquired resistance. This content is only available as a PDF. Copyright © 1995 by American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)
Overexpression of [delta]-Pyrroline-5-Carboxylate Synthetase Increases Proline Production and Confers Osmotolerance in Transgenic PlantsKishor, PBK.; Hong, Z.; Miao, G. H.; Hu, CAA.; Verma, DPS.
doi: 10.1104/pp.108.4.1387pmid: 12228549
Abstract Proline (Pro) accumulation has been correlated with tolerance to drought and salinity stresses in plants. Therefore, overproduction of Pro in plants may lead to increased tolerance against these abiotic stresses. To test this possibility, we overexpressed in tobacco the mothbean [delta]-pyrroline-5-carboxylate synthetase, a bifunctional enzyme able to catalyze the conversion of glutamate to [delta]-pyrroline-5-carboxylate, which is then reduced to Pro. The transgenic plants produced a high level of the enzyme and synthesized 10- to 18-fold more Pro than control plants. These results suggest that activity of the first enzyme of the pathway is the rate-limiting factor in Pro synthesis. Exogenous supply of nitrogen further enhanced Pro production. The osmotic potentials of leaf sap from transgenic plants were less decreased under water-stress conditions compared to those of control plants. Overproduction of Pro also enhanced root biomass and flower development in transgenic plants under drought-stress conditions. These data demonstrated that Pro acts as an osmoprotectant and that overproduction of Pro results in the increased tolerance to osmotic stress in plants. This content is only available as a PDF. Copyright © 1995 by American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)
Expression of Two Related Vacuolar H+-ATPase 16-Kilodalton Proteolipid Genes Is Differentially Regulated in a Tissue-Specific MannerHasenfratz, M. P.; Tsou, C. L.; Wilkins, T. A.
doi: 10.1104/pp.108.4.1395pmid: 7659746
Abstract The 16-kD proteolipid subunit is the principal integral membrane protein of the vaculor H+-ATPase (V-ATPase) complex that forms the proton channel responsible for translocating protons across lipid bilayers. Two degenerate synthetic oligonucleotides, COT11 and COT12, corresponding to highly conserved transmembrane domains in all 16-kD subunits sequenced so far, were used to amplify a partial cDNA of the V-ATPase proteolipid subunit from cotton (Gossypium hirsutum L.) by polymerase chain reaction (PCR). These PCR products were used to isolate two full-length cDNAs from a -3 d postanthesis cotton ovule library. Both clones, CVA16.2 and CVA16.4, consisting of 816 and 895 bp, respectively, encode the 16-kD proteolipid subunit of the V-ATPase. At the nucleotide level, the complete sequences of the two clones show 73.5% identity, but share about 95% identity within the coding region, although the two polypeptides differ by only one amino acid. Comparison of deduced amino acid sequences of the proteolipid subunits revealed that the four transmembrane domains and the two cytosolic extramembrane domains are highly conserved in all eukaryotes. Southern blot analysis of cotton genomic DNA showed that these clones belong to small gene families in related diploid and allotetraploid species. Northern blot analysis suggested that the three major V-ATPase subunits (69, 60, and 16 kD) are coordinately regulated, in part, at the transcriptional level. RNA analysis and reverse-transcription PCR established that 16-kD proteolipid transcripts differentially accumulate in different tissues and increase dramatically in tissues undergoing rapid expansion, particularly in anthers, ovules, and petals. The CVA16.4 proteolipid transcript is the most prevalent of the two proteolipid messages in expanding ovules harvested 10 d postanthesis. In contrast, the two proteolipid mRNAs accumulate to similar levels in developing petals. This content is only available as a PDF. Copyright © 1995 by American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)
Pollination-Induced Ethylene in Carnation (Role of Pollen Tube Growth and Sexual Compatibility)Larsen, P. B.; Ashworth, E. N.; Jones, M. L.; Woodson, W. R.
doi: 10.1104/pp.108.4.1405pmid: 12228550
Abstract The pollen-pistil interactions that result in the stimulation of ethylene production and petal senescence in carnation (Dianthus caryophyllus L.) flowers were investigated. Pollination of White Sim flowers with Starlight pollen elicited an increase in ethylene production by styles, leading to increased petal ethylene and premature petal senescence. In contrast, pollination with 87–29G pollen led to an early increase in ethylene production, but this was not sustained, and did not lead to petal senescence. Both Starlight and 87–29G pollen germinated on White Sim stigmas and their tubes grew at similar rates, penetrating the length of the style. Crosses between Starlight and White Sim led to the production of viable seeds, whereas 87–29G pollen was infertile on White Sim flowers. Pollination of other carnations with 87–29G elicited ethylene production and petal senescence and led to the production of viable seeds. These results suggest that physical growth of pollen tubes is insufficient to elicit a sustained increase in ethylene production or to lead to the production of signals necessary for elicitation of petal ethylene production and senescence. Rather, the cell-cell recognition reactions leading to sexual compatibility in Dianthus appear to play a role in this interorgan signaling after pollination. This content is only available as a PDF. Copyright © 1995 by American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)
Impaired Wound Induction of 3-Deoxy-D-arabino-heptulosonate-7-phosphate (DAHP) Synthase and Altered Stem Development in Transgenic Potato Plants Expressing a DAHP Synthase Antisense ConstructJones, J. D.; Henstrand, J. M.; Handa, A. K.; Herrmann, K. M.; Weller, S. C.
doi: 10.1104/pp.108.4.1413pmid: 12228551
Abstract Potato (Solanum tuberosum L.) cells were transformed with an antisense DNA construct encoding part of 3-deoxy-D-arabino-heptulosonate-7-phosphate (DAHP) synthase (EC 4.1.2.15), the first enzyme of the shikimate pathway, to examine the role(s) of this protein in plant growth and development. Chimeric DNA constructs contained the transcript start site, the first exon, and part of the first intron of the shkA gene in antisense or sense orientations under the control of the cauliflower mosaic virus 35S promoter. Some, but not all, of the transgenic plants expressing antisense DAHP synthase RNA showed reduced levels of wound-induced DAHP synthase enzyme activity, polypeptide, and mRNA 12 and 24 h after wounding. No alteration in the wound induction of DAHP synthase gene expression was observed in transgenic potato tubers containing the chimeric sense construct. Reduced steady-state levels of DAHP synthase mRNA were observed in stem and shoot tip tissue. Some plants with the chimeric antisense construct had reduced stem length, stem diameter, and reduced stem lignification. This content is only available as a PDF. Copyright © 1995 by American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)
The Effects of Cytokinin and Light on Hypocotyl Elongation in Arabidopsis Seedlings Are Independent and AdditiveSu, W.; Howell, S. H.
doi: 10.1104/pp.108.4.1423pmid: 12228552
Abstract Cytokinin has been reported to mimic some of the effects of light on de-etiolation responses in dark-grown Arabidopsis seedlings. The interaction between cytokinin and light was examined by analyzing cytokinin dose and light fluence effects on hypocotyl elongation in wild-type and mutant Arabidopsis seedlings with defects in light or hormone responses. It was found that (a) cytokinin and light-response systems have independent and additive effects on the inhibition of hypocotyl elongation and (b) either cytokinin or light can saturate the morphogenic responses. As a consequence, cytokinin has no effect on hypocotyl elongation under normal growth conditions because light levels saturate the hypocotyl inhibition response. To determine whether a functional light-response pathway is required for cytokinin responses, light-insensitive long hypocotyl (hy) mutants were tested for cytokinin responses. The hy mutants (hy1 to hy6) had normal cytokinin responses, except phyB-1 (hy3–1), in which hypocotyl elongation was insensitive to cytokinin. Cytokinin insensitivity in phyB-1 was attributed to an indirect effect of the mutation on cytokinin responses. The effects of cytokinin on the inhibition of hypocotyl elongation are largely mediated by ethylene, and blocking the ethylene-response pathway through the action of a cytokinin-resistant, ethylene-insensitive mutant (ckr1/ein2) had no effect on the light inhibition of hypocotyl elongation. These results do not support the idea that cytokinin mediates the action of light on hypocotyl elongation. This content is only available as a PDF. Copyright © 1995 by American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)
Photosynthetic Shutdown in Chlorella NC64A Associated with the Infection Cycle of Paramecium bursaria Chlorella Virus-1Seaton, GGR.; Lee, K.; Rohozinski, J.
doi: 10.1104/pp.108.4.1431pmid: 12228553
Abstract The effects of the algal virus Paramecium bursaria Chlorella virus-1 on the photosynthetic physiology of its host, Chlorella NC64A, was studied by observing changes in Chl fluorescence quenching and O2 exchange. Metabolic changes were calibrated against electron microscopic analysis of the morphological changes that occur during the infection cycle. It takes approximately 10 h from attachment of the virus to final lysis of the host cell, so a complete infection cycle can be observed continuously in one experiment. During the early stages of the infection cycle many rapid changes occurred in the host cell's metabolism and these were reflected in changes of photosynthetic and respiratory rates. The dramatic inhibition of photosynthesis in Chlorella NC64A cells by P. bursaria Chlorella virus-1 has facilitated the use of fluorescence quenching as an accurate measure of the first phase of viral infection (attachment and penetration of the host cell) and the extent to which a population of host cells is infected. Effects of temperature and cation requirement of the infection cycle are described. The relevance of our observations to the events observed during viral infection of higher plants is discussed. This content is only available as a PDF. Copyright © 1995 by American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)