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Biomedical subjects

J O Berry

Publications and source records attributed to J O Berry.

14 recordsLinked to original sources
PubMed2000

Light-associated and processing-dependent protein binding to 5' regions of rbcL mRNA in the chloroplasts of a C4 plant.

In amaranth, a C(4) dicotyledonous plant, the plastid rbcL gene (encoding the large subunit of ribulose-1,5-bisphosphate carboxylase) is regulated post-transcriptionally during many developmental processes, including light-mediated development. To identify post-transcriptional regulators of rbcL expression, three types of analyses (polysome heel printing, gel retardation, and UV cross-linking) were utilized. These approaches revealed that multiple proteins interact with 5' regions of rbcL mRNA in light-grown, but not etiolated, amaranth plants. Light-associated binding of a 47-kDa protein (p47), observed by UV cross-linking, was highly specific for the rbcL 5' RNA. Binding of p47 occurred only with RNAs corresponding to mature processed rbcL transcripts (5'-untranslated region (UTR) terminating at -66); transcripts with longer 5'-UTRs did not associate with p47 in vitro. Variations in the length of the rbcL 5'-UTR were found to occur in vivo, and these different 5' termini may prevent or enhance light-associated p47 binding, possibly affecting rbcL expression as well. p47 binding correlates with light-dependent rbcL polysome association of the fully processed transcripts in photosynthetic leaves and cotyledons but not with cell-specific rbcL mRNA accumulation in bundle sheath and mesophyll chloroplasts.

5' Untranslated Regions↗
PubMed1996

High-level secretion of a virally encoded anti-fungal toxin in transgenic tobacco plants.

Ustilago maydis killer toxins are small polypeptides (7-14 kDa) which kill susceptible cells of closely related fungal species. The KP4 toxin is a single polypeptide subunit with a molecular weight of 11.1 kDa. In this work, a transgenic tobacco plant was constructed which secretes the KP4 toxin at a high level. The KP4 toxin expressed in this transgenic plant was of the same size and specificity as the authentic Ustilago KP4 toxin. The expression level was at least 500 times higher than that of the KP6 toxin expressed in plants. Transgenic crop plants producing the KP4 toxin could be rendered resistant to KP4-susceptible fungal pathogens.

Molecular Probe Techniques↗
PubMed1995

Processing and secretion of a virally encoded antifungal toxin in transgenic tobacco plants: evidence for a Kex2p pathway in plants.

Ustilago maydis is a fungal pathogen of maize. Some strains of U. maydis encode secreted polypeptide toxins capable of killing other susceptible strains of U. maydis. We show here that one of these toxins, the KP6 killer toxin, is synthesized by transgenic tobacco plants containing the viral toxin cDNA under the control of a cauliflower mosaic virus promoter. The two components of the KP6 toxin, designated alpha and beta, with activity and specificity identical to those found in toxin secreted by U. maydis cells, were isolated from the intercellular fluid of the transgenic tobacco plants. The beta polypeptide from tobacco was identical in size and N-terminal sequence to the U. maydis KP6 beta polypeptide. Processing of the KP6 preprotoxin in U. maydis requires a subtilisin-like processing protease, Kex2p, which is present in both animal and fungal cells and is required for processing of (among other things) small secreted polypeptide hormones and secreted toxins. Our findings present evidence for Kex2p-like processing activity in plants. The systemic production of this viral killer toxin in crop plants may provide a new method of engineering biological control of fungal pathogens in crop plants.

Cloning, Molecular↗
PubMed1994

Cloning and analysis of the C4 photosynthetic NAD-dependent malic enzyme of amaranth mitochondria.

In some C4 plant species, a mitochondrial NAD-dependent malic enzyme (EC 1.1.1.39) (NAD-ME) catalyzes the decarboxylation of 4 carbon malate in the bundle sheath cells, releasing CO2 for the Calvin cycle of photosynthesis. In amaranth, a dicotyledonous NAD-ME-type C4 plant, the photosynthetic NAD-ME purified as two subunits of 65 and 60 kDa, designated alpha and beta, respectively. Antiserum raised against the alpha subunit reacted only with the 65-kDa protein in immunoblot analysis. Immunogold electron microscopy using the alpha subunit antiserum demonstrated that this protein was localized specifically to the mitochondrial matrix of bundle sheath cells. The complete nucleotide sequence of a 2300-base pair alpha subunit cDNA clone showed that this gene encodes a protein that contains all of the motifs required for a complete and functional malic enzyme. The alpha subunit has significant similarity along its entire length to other known NAD- and NADP-dependent malic enzymes from plants, animals, and bacteria. The findings presented here provide new insights about the C4 photosynthetic NAD-ME and its evolutionary relationship to other forms of malic enzyme present in eukaryotic and prokaryotic organisms.

Amino Acid Sequence↗
PubMed1993

Post-transcriptional control of cell type-specific gene expression in bundle sheath and mesophyll chloroplasts of Amaranthus hypochondriacus.

Plants that utilize the highly efficient C4 photosynthetic pathway possess two types of specialized leaf cells, the mesophyll and bundle sheath. In mature leaves of amaranth, a dicotyledonous C4 plant, ribulose 1,5-bisphosphate carboxylase (Rubisco) is localized specifically to the chloroplasts of bundle sheath cells, and is not present in the chloroplasts of mesophyll cells. The cell type-specific expression of the chloroplast-encoded Rubisco large subunit (rbcL) gene, and other representative chloroplastic genes, was investigated by using separated bundle sheath and mesophyll chloroplasts prepared from mature amaranth leaves. One-dimensional SDS-polyacrylamide gel electrophoresis revealed several differences in the polypeptide compositions of the two chloroplast types. Western analysis demonstrated that, as in the intact leaves, the Rubisco LSU polypeptide was present only in chloroplast preparations from bundle sheath cells. Pyruvate orthophosphate dikinase (PPdK), a nuclear-encoded chloroplastic enzyme, was found only in the mesophyll chloroplast preparations. rbcL mRNA was present only in the bundle sheath chloroplast preparations, whereas transcripts for the chloroplast-encoded psbA, psaA-B, and rpl2 genes were present in both chloroplast types. Although the rbcL message accumulated only in bundle sheath chloroplasts, run-on transcription analysis indicated that the rbcL gene was transcribed in both bundle sheath and mesophyll chloroplast preparations. Therefore, differential rbcL gene expression in the isolated C4 chloroplasts is regulated, at least in part, at the post-transcriptional level. Possibly this control is mediated by differential processing or stabilization of the rbcL transcript.

Chloroplasts↗
PubMed1991

Situational and dispositional components of reactions toward persons with disabilities.

The situational and dispositional components of reactions toward disabled persons were investigated in a hypothetical format. Initially, a sample of American college students (n = 194) indicated the level of anticipated emotional arousal to 70 brief descriptions of situations in which contact with disabled people might occur on a college campus. Mean ratings were used to select nine situation descriptors representing a range of anticipated arousal levels. Subsequently, a separate sample of students (n = 164) completed the Attitudes Toward Disabled Persons Scale (Yuker, Block, & Younng, 1966) and were presented with one of the nine situation descriptors. Participants imagined themselves in the situation described (with a person with an immediately obvious disability) and indicated how they would feel and respond by completing various measures. Results indicated that emotional arousal and other reactions were attributable to main effects for both situational and attitudinal factors, whereas the statistical interactions between the two were not significant.

Adolescent↗
PubMed1990

Light-mediated control of translational initiation of ribulose-1, 5-bisphosphate carboxylase in amaranth cotyledons.

In cotyledons of 6-day-old amaranth seedlings, the large subunit (LSU) and the small subunit (SSU) polypeptides of ribulose-1,5-bisphosphate carboxylase are not synthesized in the absence of light. When dark-grown seedlings were transferred into light, synthesis of both polypeptides was induced within the first 3 to 5 hr of illumination without any significant changes in levels of their mRNAs. In cotyledons of light-grown seedlings and of dark-grown seedlings transferred into light for 5 hr (where ribulose-1,5-bisphosphate carboxylase synthesis was readily detected in vivo), the LSU and SSU mRNAs were associated with polysomes. In cotyledons of dark-grown seedlings, these two mRNAs were not found on polysomes. In contrast to the SSU message, mRNAs encoding the nonlight-regulated, nuclear-encoded proteins actin and ubiquitin were associated with polysomes regardless of the light conditions. Similarly, mRNA from at least one chloroplast-encoded gene (rpl2) was found on polysomes in the dark as well as in the light. These results indicate an absence of translational initiation in cotyledons of dark-grown seedlings which is specific to a subset of nuclear- and chloroplast-encoded genes including the SSU and LSU, respectively. Upon illumination, synthesis of both polypeptides, and possibly other proteins involved in light-mediated chloroplast development, was induced at the level of translational initiation.

Chloroplasts↗
PubMed1988

mRNAs encoding ribulose-1,5-bisphosphate carboxylase remain bound to polysomes but are not translated in amaranth seedlings transferred to darkness.

When light-grown seedlings of amaranth are transferred to total darkness, synthesis of the large subunit (LS) and small subunit (SS) of ribulose-1,5-bisphosphate carboxylase [RbuP(2)Case; 3-phospho-D-glycerate carboxylase (dimerizing), EC 4.1.1.39] is rapidly depressed. This reduction in RbuP(2)Case synthesis occurs in the absence of any corresponding changes in levels of functional mRNA for either subunit. Four hours after light-to-dark transition little, if any, changes in the distribution of LS and SS mRNAs on polysomes could be detected. The association of these mRNAs with polysomes was authenticated by treatment with RNase A or puromycin. Furthermore, polysomes were able to synthesize LS and SS precursor in cell-free translation systems supplemented with inhibitors of initiation. Therefore, during a light-to-dark transition LS and SS mRNAs remained bound to polysomes but were not translated in vivo, suggesting that control is exercised, in part, at the translational elongation step.

Journal Article↗
PubMed1986

Translational regulation of light-induced ribulose 1,5-bisphosphate carboxylase gene expression in amaranth.

The regulation of the genes encoding the large and small subunits of ribulose 1,5-bisphosphate carboxylase was examined in amaranth cotyledons in response to changes in illumination. When dark-grown cotyledons were transferred into light, synthesis of the large- and small-subunit polypeptides was initiated very rapidly, before any increase in the levels of their corresponding mRNAs. Similarly, when light-grown cotyledons were transferred to total darkness, synthesis of the large- and small-subunit proteins was rapidly depressed without changes in mRNA levels for either subunit. In vitro translation or in vivo pulse-chase experiments indicated that these apparent changes in protein synthesis were not due to alterations in the functionality of the mRNAs or to protein turnover, respectively. These results, in combination with our previous studies, suggest that the expression of ribulose 1,5-bisphosphate carboxylase genes can be adjusted rapidly at the translational level and over a longer period through changes in mRNA accumulation.

Electrophoresis, Polyacrylamide Gel↗
PubMed1985

Transcriptional and post-transcriptional regulation of ribulose 1,5-bisphosphate carboxylase gene expression in light- and dark-grown amaranth cotyledons.

The regulation of expression of the genes encoding the large subunit (LSU) and small subunit (SSU) of ribulose 1,5-bisphosphate carboxylase (RuBPCase) was examined in 1- through 8-day-old, dark-grown (etiolated) and light-grown amaranth cotyledons. RuBPCase specific activity in light-grown cotyledons increased during this 8-day period to a level 15-fold higher than in dark-grown cotyledons. Under both growth conditions, the accumulation of the LSU and SSU polypeptides was not coordinated. Initial detection of the SSU occurred 1 and 2 days after the appearance of the LSU in light- and dark-grown cotyledons, respectively. Furthermore, although the levels of the LSU were similar in both light- and dark-grown seedlings, the amount of the SSU followed clearly the changes in enzyme activity. Synthesis of these two polypeptides was dramatically different in etiolated versus light-grown cotyledons. In light the synthesis of both subunits was first observed on day 2 and continued throughout the growth of the cotyledons. In darkness the rate of synthesis of both subunits was much lower than in light and occurred only as a burst between days 2 and 5 after planting. However, mRNAs for both subunits were present in etiolated cotyledons at similar levels on days 4 through 7 (by Northern analysis) and were functional in vitro, despite their apparent inactivity in vivo after day 5. In addition, since both LSU and SSU mRNA levels were lower in dark- than in light-grown seedlings, our results indicate that both transcriptional and post-transcriptional controls modulate RuBPCase production in developing amaranth cotyledons.

Gene Expression Regulation↗
PubMed1984

Induced plasmid-genome rearrangements in Rhizobium japonicum.

The P group resistance plasmids RP1 and RP4 were introduced into Rhizobium japonicum by polyethylene-glycol-induced transformation of spheroplasts. After cell wall regeneration, transformants were recovered by selecting for plasmid determinants. Plant nodulation, nitrogen fixation, serological, and bacterial genetics studies revealed that the transformants were derived from the parental strains and possessed the introduced plasmid genetic markers. Agarose gel electrophoresis, restriction enzyme analysis, and DNA hybridization studies showed that many of the transformant strains had undergone genome rearrangements. In the RP1 transformants, chromosomal DNA was found to have transposed into a large indigenous plasmid of R. japonicum, producing an even larger plasmid, and the introduced R plasmid DNA was found to be chromosomally integrated rather than replicating autonomously or integrated into the endogenous plasmid. Seemingly, a similar section of chromosomal DNA was involved in all the genomic rearrangements observed in the R. japonicum RP1 and RP4 transformant strains.

Chromosomes, Bacterial↗