scholarly journals LX Senescence-Induced Ribonuclease in Tomato: Function and Regulation

2003 ◽  
Author(s):  
Amnon Lers ◽  
Pamela J. Green
Keyword(s):  
Leaf Senescence ◽  
Higher Plants ◽  
Optimal Growth ◽  
Growth Conditions ◽  
Specific Gene ◽  
Transcriptional Level ◽  
General View ◽  
Type I ◽  
Degrading Enzymes ◽  
Nucleolytic Activity

Natural leaf senescence, which occurs even when growth conditions are near optimal, has a negative influence on yield. Postharvest induced senescence contributes to the losses of quality in flowers, foliage, and vegetables. Strategies designed to control the senescence process in crop plants could therefore have great applied significance. However, the successful design of such strategies requires a better insight into the senescence machinery and control in higher plants. A main feature of senescence is the hydrolysis of macromolecules by hydrolases of various types such as ribonucleases (RNases) and proteases. Previously we had identified and characterized the tomato LX RNase gene demonstrating its transcript to be highly and specifically induced during senescence. This reported study was focused on LX but also had broadened our research to other senescence-associated nucleic acids degrading enzymes to learn about their function and the regulation of their encoding genes. Beside tomato we used parsley and Arabidopsis for the study of: the bi-functional nuclease which has a role in senescence. The study of different senescence- associated nucleases in few plant systems will allow a more general view on function and regulation of these enzymes in senescence. The specific original proposed objectives included: 1. Study the consequences of alterations in LX RNase level on tomato leaf senescence and general development; 2. Analyze stimuli which may participate in senescence-specific activation of the LX gene; 3. Clone the senescence-associated BFNI nuclease gene homologue from tomato. 4. Further characterize the sequences required for senescence-specific gene expression. Homozygous transgenic plants in which LX gene was either inhibited or over-expressed were generated. In both of these LX mutated plants no major phenotypic consequences were observed, which may suggests that LX is not essential for plant growth under optimal growth conditions. Lack of any abnormalities in the LX over-expressing lines suggests that special system exist to allow function of the RNase only when needed. Detailed analyses of growth under stress and consequences to RNA metabolism are underway. We have analyzed LX expression on the protein level demonstrating that it is involved also in petal senescing. Our results suggest that LX is responding to complex regulation involving developmental, organ dependent factors and responds differently to hormonal or environmental stimuli in the different plant organs. The cloned 1.4 kb promoter was cloned and its analysis revealed that probably not all required elements for senescence induction are included. Biochemical analysis of senescence-associated be-functional nucleases in the different plants, tomato, parsley and Arabidopsis, suggests they belong to a sub-class within the type I plant nucleases. The parsley PcNUC1/2 nuclease protein was purified from senescing leaves its and activity was studied in vitro revealing endo-, double strand, nucleolytic activity and exo-nucleolytic activity. Its encoding gene was cloned and found to be induced on the mRNA level. The promoter of the related Arabidopsis BFNI nuclease was shown in both tomato and Arabidopsis to be able and direct senescence-specific expression suggesting that, at least part, the gene is regulated on the transcriptional level and that the mechanism for this senescence-specific regulation is conserved between different plants. Few plants in which the BFNI gene is mutated were identified which are subjected now to detailed analysis. Our results suggest that the senescence-related nucleic acid degrading enzymes share similarities in both function and regulation between different plants and possibly have important functions in processes un-related to senescence. Still, the function of these enzymes, at least in some cases is not essential to plant development under optimal growth conditions. We are now at the stage which permits in depth investigation of the specific functions and mode of molecular regulation of senescence-associated nucleases with the aid of the research tools developed. The isolated senescence-specific promoter, shown to be active in heterologous plant system, could be utilized in agricultural-related biotechnological applications for retardation of senescence.

POPULATION STUDIES IN MICROORGANISMS I. EVOLUTION OF DIPLOIDY IN SACCHAROMYCES CEREVISIAE

Genetics ◽  
1974 ◽  
Vol 76 (2) ◽  
pp. 327-338
Author(s):  
Julian Adams ◽  
Paul E Hansche
Keyword(s):  
Higher Plants ◽  
Volume Ratio ◽  
Optimal Growth ◽  
Growth Conditions ◽  
Reproductive Rate ◽  
Low Concentrations ◽  
Reproductive Rates ◽  
Diploid Cells ◽  
Dominant Phase ◽  
Reduced Surface

ABSTRACT The relative adaptation of isogenic haploid and diploid strains of yeast was investigated in different sets of physiological conditions. When all nutrients were present in excess, no difference in the reproductive rates of isogenic haploid and diploid strains of yeast was detected in both optimal and non-optimal growth conditions. Competition between haploid and diploid strains of yeast was observed when growth was limited by the concentration of a single nutrilite. Under certain conditions when fitness (reproductive rate) is determined by transport of an essential nutrilite that exists in very low concentrations, diploid cells were selected against. These environmental conditions are similar to those found in offshore marine environments where nutrients are often present in extremely low concentrations. The fitness of diploid cells was estimated to be.93 ±.02 (haploid fitness = 1). The reduced fitness of diploid cells in this environment can be explained by the reduced surface area/volume ratio possessed by diploid cells in comparison to haploid cells. The fitnesses of haploid and diploid cells in these environments are closely correlated with geometric variations in these strains. These results are consistent with the hypothesis that diploid cells are simply double haploids, and diploidy per se does not confer any direct adaptive advantage. The mechanism of the evolution of diploidy as a dominant phase in the life cycle of higher plants and animals remains obscure.

scholarly journals Isolation of a gene required for programmed initiation of development by Aspergillus nidulans.

1992 ◽  
Vol 12 (9) ◽  
pp. 3827-3833 ◽  
Author(s):  
T H Adams ◽  
W A Hide ◽  
L N Yager ◽  
B N Lee
Keyword(s):  
Life Cycle ◽  
Aspergillus Nidulans ◽  
Optimal Growth ◽  
Growth Conditions ◽  
Nutrient Deprivation ◽  
Deletion Mutants ◽  
Wild Type ◽  
Microbial Development ◽  
Type Strains ◽  
Posttranscriptional Level

In contrast to many other cases in microbial development, Aspergillus nidulans conidiophore production initiates primarily as a programmed part of the life cycle rather than as a response to nutrient deprivation. Mutations in the acoD locus result in "fluffy" colonies that appear to grow faster than the wild type and proliferate as undifferentiated masses of vegetative cells. We show that unlike wild-type strains, acoD deletion mutants are unable to make conidiophores under optimal growth conditions but can be induced to conidiate when growth is nutritionally limited. The requirement for acoD in conidiophore development occurs prior to activation of brlA, a primary regulator of development. The acoD transcript is present both in vegetative hyphae prior to developmental induction and in developing cultures. However, the effects of acoD mutations are detectable only after developmental induction. We propose that acoD activity is primarily controlled at the posttranscriptional level and that it is required to direct developmentally specific changes that bring about growth inhibition and activation of brlA expression to result in conidiophore development.

scholarly journals The dyskerin ribonucleoprotein complex as an OCT4/SOX2 coactivator in embryonic stem cells

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Yick W Fong ◽  
Jaclyn J Ho ◽  
Carla Inouye ◽  
Robert Tjian
Keyword(s):  
Stem Cell ◽  
Es Cells ◽  
Embryonic Stem ◽  
In Vitro Transcription ◽  
Specific Gene ◽  
Transcriptional Level ◽  
Ips Cell ◽  
Ribonucleoprotein Complex ◽  
Transcription System

Acquisition of pluripotency is driven largely at the transcriptional level by activators OCT4, SOX2, and NANOG that must in turn cooperate with diverse coactivators to execute stem cell-specific gene expression programs. Using a biochemically defined in vitro transcription system that mediates OCT4/SOX2 and coactivator-dependent transcription of the Nanog gene, we report the purification and identification of the dyskerin (DKC1) ribonucleoprotein complex as an OCT4/SOX2 coactivator whose activity appears to be modulated by a subset of associated small nucleolar RNAs (snoRNAs). The DKC1 complex occupies enhancers and regulates the expression of key pluripotency genes critical for self-renewal in embryonic stem (ES) cells. Depletion of DKC1 in fibroblasts significantly decreased the efficiency of induced pluripotent stem (iPS) cell generation. This study thus reveals an unanticipated transcriptional role of the DKC1 complex in stem cell maintenance and somatic cell reprogramming.

scholarly journals Characterization of the Antibiotic Compound No. 70 Produced byStreptomycessp. IMV-70

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Lyudmila P. Trenozhnikova ◽  
Almagul K. Khasenova ◽  
Assya S. Balgimbaeva ◽  
Galina B. Fedorova ◽  
Genrikh S. Katrukha ◽  
...  
Keyword(s):  
Optimal Growth ◽  
Growth Conditions ◽  
Culture Broth ◽  
Producer Strain ◽  
New Class ◽  
New Antibiotics ◽  
Actinomycete Strain ◽  
Main Component

We describe the actinomycete strain IMV-70 isolated from the soils of Kazakhstan, which produces potent antibiotics with high levels of antibacterial activity. After the research of its morphological, chemotaxonomic, and cultural characteristics, the strain with potential to be developed further as a novel class of antibiotics with chemotherapeutics potential was identified asStreptomycessp. IMV-70. In the process of fermentation, the strainStreptomycesspp. IMV-70 produces the antibiotic no. 70, which was isolated from the culture broth by extraction with organic solvents. Antibiotic compound no. 70 was purified and separated into individual components by HPLC, TLC, and column chromatography methods. The main component of the compound is the antibiotic 70-A, which was found to be identical to the peptolide etamycin A. Two other antibiotics 70-B and 70-C have never been described and therefore are new antibiotics. The physical-chemical and biological characteristics of these preparations were described and further researched. Determination of the optimal growth conditions to cultivate actinomycete-producer strain IMV-70 and development of methods to isolate, purify, and accumulate preparations of the new antibiotic no. 70 enable us to research further the potential of this new class of antibiotics.

scholarly journals The PSY Peptide Family—Expression, Modification and Physiological Implications

Genes ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 218
Author(s):  
Amalie Scheel Tost ◽  
Astrid Kristensen ◽  
Lene Irene Olsen ◽  
Kristian Buhl Axelsen ◽  
Anja Thoe Fuglsang
Keyword(s):  
Plant Development ◽  
Higher Plants ◽  
Expression Patterns ◽  
Transcriptional Level ◽  
Amino Acid Peptide ◽  
Developmental Factors ◽  
Peptide Family ◽  
The Family ◽  
Modified Peptides ◽  
High Conservation

Small post-translationally modified peptides are gaining increasing attention as important signaling molecules in plant development. In the family of plant peptides containing tyrosine sulfation (PSYs), only PSY1 has been characterized at the mature level as an 18-amino-acid peptide, carrying one sulfated tyrosine, and involved in cell elongation. This review presents seven additional homologs in Arabidopsis all sharing high conservation in the active peptide domain, and it shows that PSY peptides are found in all higher plants and mosses. It is proposed that all eight PSY homologs are post-translationally modified to carry a sulfated tyrosine and that subtilisin-like subtilases (SBTs) are involved in the processing of PSY propeptides. The PSY peptides show differential expression patterns indicating that they serve several distinct functions in plant development. PSY peptides seem to be at least partly regulated at the transcriptional level, as their expression is greatly influenced by developmental factors. Finally, a model including a receptor in addition to PSY1R is proposed.

Toxic properties of Aeromonas proteolytica

1974 ◽  
Vol 20 (10) ◽  
pp. 1403-1409 ◽  
Author(s):  
B. G. Foster ◽  
Mary O. Hanna
Keyword(s):  
Thermal Stability ◽  
Culture Filtrate ◽  
Hemolytic Activity ◽  
Optimal Growth ◽  
Growth Conditions ◽  
The Other ◽  
Activity Peak ◽  
Endopeptidase Activity ◽  
Time Periods ◽  
Thermal Stability Of

Aeromonas proteolytica was grown for various time periods in nutrient broth, tryptic soy broth, a semisynthetic medium, and 1 and 5% peptone under different conditions involving temperature and in continuous shake and stationary flasks. The cell-free culture filtrates were tested for hemolytic, endopeptidase, and dermonecrotic activity and optimal growth conditions for their production were determined. The dermonecrotic activity and endopeptidase activity was found to be parallel in all tests, while hemolysin was independent of the other two. Studies on the thermal stability of the culture filtrate revealed that hemolysin and dermonecrotic and endopeptidase activity were destroyed at 70 °C for 30 min. Fractionation of the filtrate by Sephadex G-200 resolved three peaks at 280 nm. Peak I was inactive; peak II contained endopeptidase and dermonecrotic and hemolytic activity; peak III contained pigment and hemolysin. Evidence is presented that the endopeptidase and dermonecrotic substance found in the cell-free filtrates of A. proteolytica grown medium appear at the same time and thus may be the same entity.

Structure of the two promoters of the human lck gene: differential accumulation of two classes of lck transcripts in T cells

1989 ◽  
Vol 9 (5) ◽  
pp. 2173-2180
Author(s):  
T Takadera ◽  
S Leung ◽  
A Gernone ◽  
Y Koga ◽  
Y Takihara ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Cell Lines ◽  
Carcinoma Cell ◽  
Human Peripheral Blood ◽  
Specific Gene ◽  
Type I ◽  
Type Ii ◽  
Carcinoma Cell Lines ◽  
Human T Cell

The human T-cell- or lymphocyte-specific gene, lck, encodes a tyrosine kinase and is a member of the src family. In this report we demonstrate that there are two classes of human lck transcripts (types I and II), containing different 5'-untranslated regions, which are expressed from two distinct promoters. No apparent sequence similarity was observed between the 5'-flanking regions of the two promoters. The expression of lck in human T-cell leukemia and carcinoma cell lines and in human peripheral blood T lymphocytes was examined by S1 nuclease and primer extension mapping and by Northern (RNA) blot analysis of total cellular RNA. The following results were obtained. (i) Two RNA start sites in the downstream promoter were used to generate type I transcripts. (ii) The major human type I start site has not been described for the mouse. (iii) At least five RNA start sites in the upstream promoter were used to generate type II transcripts. (iv) In T cells and in two colon carcinoma cell lines, type II transcripts were present in higher amounts than type I transcripts. (v) In T cells treated with phytohemagglutinin, tetradecanoylphorbol acetate, and cyclosporin A, the modulation of lck expression was associated primarily with changes in levels of type II transcripts. The above results suggest that the two human lck promoters are utilized differentially and may be regulated independently during certain physiological states.

Identification of Arabidopsis stay-green mutants with a functional ethylene-response pathway

2010 ◽  
Vol 14 ◽  
pp. 119-129
Author(s):  
R. Shirzadian-Khorramabad ◽  
H.C. Jing ◽  
J. Hille ◽  
P.P. Dijkwel
Keyword(s):  
Shelf Life ◽  
Leaf Senescence ◽  
Plant Hormone ◽  
Floral Induction ◽  
Growth Conditions ◽  
Pleiotropic Effects ◽  
Wild Type ◽  
Stay Green ◽  
Ethylene Response ◽  
Determinant Factor

Natural or harvest-induced senescence is a major determinant factor causing crop losses. The plant hormone ethylene is a strong inducer of senescence and decreasing the ethylene response can reduce senescence, albeit often with undesirable pleiotropic effects. We took advantage of ethylene-induced leaf senescence as a tool to screen for late senescence Arabidopsis mutants that still have a functional ethylenesignalling pathway. Sixteen Arabidopsis onset of leaf death (old) mutants were selected that stayed green after treatment with ethylene. While all the mutants responded to ethylene in a triple response assay, ten mutants responded to the treatment in the same way as the wild type. These ten mutants showed limited pleiotropic effects when grown under standard growth conditions but nine mutants flowered slightly later than the wild type. Genetic characterisation of a subset of the mutants identified several independent loci controlling the leaf senescence process. The approach resulted in the isolation of several stay-green mutants with a functional ethylene response pathway. The late senescence mutants show extended leaf longevity and further research may advance the field of pre- or post-harvest senescence technology. The results, moreover, suggest that there is a correlation between senescence and floral induction. Keywords: Senescence, Arabidopsis, ethylene, mutant, shelf life

Differential elimination of rDNA genes in bobbed mutants of Drosophila melanogaster

1986 ◽  
Vol 6 (4) ◽  
pp. 1023-1031
Author(s):  
R Terracol ◽  
N Prud'homme
Keyword(s):  
Drosophila Melanogaster ◽  
Gene Copy Number ◽  
Rdna Locus ◽  
Gene Copy ◽  
Specific Gene ◽  
Type I ◽  
28S Rrna ◽  
Wild Type ◽  
Y Chromosomes ◽  
Genes Encoding

In Drosophila melanogaster, the multiply repeated genes encoding 18S and 28S rRNA are located on the X and Y chromosomes. A large percentage of these repeats are interrupted in the 28S region by insertions of two types. We compared the restriction patterns from a subcloned wild-type Oregon R strain to those of spontaneous and ethyl methanesulfonate-induced bobbed mutants. Bobbed mutations were found to be deficiencies that modified the organization of the rDNA locus. Genes without insertions were deleted about twice as often as genes with type I insertions. Type II insertion genes were not decreased in number, except in the mutant having the most bobbed phenotype. Reversion to wild type was associated with an increase in gene copy number, affecting exclusively genes without insertions. One hypothesis which explains these results is the partial clustering of genes by type. The initial deletion could then be due either to an unequal crossover or to loss of material without exchange. Some of our findings indicated that deletion may be associated with an amplification phenomenon, the magnitude of which would be dependent on the amount of clustering of specific gene types at the locus.

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