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  • Rice  (109)
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  • 1
    ISSN: 1432-2242
    Keywords: Key words Cold stress ; Ca2+-dependent protein kinase ; In-gel phosphorylation assay ; Rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Ca2+-dependent protein kinases (CDPKs) play an important role in plant signal transduction. Protein kinase(s) activities induced by 5°C cold stress in rice (Oryza sativa L.) seedlings were investigated in both leaf and stem tissues in an early (up to 45 min) and late (up to 12 h) response study. The leaf had 37-, 47- and 55-kDa protein kinase activities, and the stem had 37-, 47- and 55-kDa protein kinase activities. A 16-kDa protein showed constitutive kinase activity in the rice seedling leaf and stem. It was further identified that the 47-kDa protein kinase activity induced by cold in both the cytosolic and membrane fractions of the stem was strictly Ca2+-dependent. This CDPK activitiy increased in the presence of the Ca2+ ionophore A23187 in stem segments, whereas it was decreased by the Ca2+ channel blocker, LaCl3, and the Ca2+ chelator, EGTA. The general protein kinase inhibitor, staurosporine, completely inhibited this CDPK activity in vitro, and both W7, a calmodulin antagonist, and H7, a protein kinase C inhibitor, could only partially decrease this activity. The protein phosphatase inhibitor, okadaic acid, increased CDPK activity. This CDPK activity was also induced by salt, drought stress and the phytohormone abscicic acid. Among the 18 rice varieties tested, this cold-induced 47-kDa CDPK activity was stronger in the cold-tolerant varieties than in the sensitive ones.
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  • 2
    ISSN: 1432-2242
    Keywords: Keywords Fragrance ; Rice ; PCR marker ; Oryza sativa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The genomic DNA clone RG28, linked to the major fragrance gene of rice (fgr), was assessed for polymorphism in order to produce a PCR-based marker for fragrance. A small mono-nucleotide repeat, that was polymorphic between a pair of fragrant and non-fragrant cultivars, was identified and developed into a co-dominant PCR-based marker. The polymorphism-information-content determinations for three microsatellite markers, that have been genetically mapped near RG28, are also presented. These PCR-based markers will be highly useful in distinguishing fragrance-producing alleles from non-fragrance-producing alleles at the fgr locus.
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  • 3
    ISSN: 1432-2242
    Keywords: Key words  Cell membrane stability ; Drought resistance ; Oryza sativa ; QTLs ; Rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Cell-membrane stability (CMS) is considered to be one of the major selection indices of drought tolerance in cereals. In order to determine which genomic region is responsible for CMS, 104 rice (Oryza sativa L.) doubled haploid (DH) lines derived from a cross between CT9993–5-10–1-M and IR62266-42–6-2 were studied in the greenhouse in a slowly developed drought stress environment. Drought stress was induced on 50-day-old plants by withholding water. The intensity of stress was assessed daily by visual scoring of leaf wilting and by measuring leaf relative water content (RWC). The leaf samples were collected from both control (well-watered) and stressed plants (at 60–65% of RWC), and the standard test for CMS was carried out in the laboratory. There was no significant difference (P〉0.05) in RWC between the two parental lines as well as among the 104 lines, indicating that all the plants were sampled at a uniform stress level. However, a significant difference (P〈0.05) in CMS was observed between the two parental lines and among the population. No significant correlation was found between CMS and RWC, indicating that the variation in CMS was genotypic in nature. The continuous distribution of CMS and its broad-sense heritability (34%) indicates that CMS should be polygenic in nature. A linkage map of this population comprising of 145 RFLPs, 153 AFLPs and 17 microsatellite markers was used for QTL analysis. Composite interval mapping identified nine putative QTLs for CMS located on chromosomes 1, 3, 7, 8, 9, 11 and 12. The amount of phenotypic variation that was explained by individual QTLs ranged from 13.4% to 42.1%. Four significant (P〈0.05) pairs of digenic interactions between the detected QTLs for CMS were observed. The identification of QTLs for this important trait will be useful in breeding for the improvement of drought tolerance in rice. This is the first report of mapping QTLs associated with CMS under a natural water stress condition in any crop plants.
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  • 4
    ISSN: 1432-2242
    Keywords: Key words Agrobacterium ; Chitinase ; T-DNA ; Sheath blight ; Rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  A concise T-DNA element was engineered containing the rice class-I chitinase gene expressed under the control of CaMV35S and the hygromycin phosphotransferase gene (hph) as a selectable marker. The binary plasmid vector pNO1 with the T-DNA element containing these genes of interest was mobilized to Agrobacterium tumefaciens strain LBA4404 to act as an efficient donor of T-DNA in the transformation of three different indica rice cultivars from different ecosystems. Many morphologically normal, fertile transgenic plants from these rice cultivars were generated after Agrobacterium-mediated transformation using 3-week-old scutella calli as initial explants. Stable integration, inheritance and expression of the chimeric chitinase gene were demonstrated by Southern blot and Western blot analysis of the transformants. Bioassay data showed that transgenic plants can restrict the growth of the sheath blight pathogen Rhizoctonia solani. Bioassay results were correlated with the molecular analysis. Although we obtained similar results upon DNA-mediated transformation, this report shows the potential of the cost-effective, simple Agrobacterium system for genetic manipulation of rice cultivars with a pathogenesis-related (PR) gene.
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  • 5
    ISSN: 1432-2242
    Keywords: Cryopreservation ; Embryo culture ; Haploids ; Wheat ; Rice ; Germplasm bank
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Anther culture derived pollen embryos and immature zygotic embryos of wheat and rice, frozen in liquid nitrogen in the presence of dimethyl sulfoxide, sucrose and glycerol, have been revived. The retrieved cultures proliferated and/or regenerated shoots and plantlets. The prospects of the cryopreservation of embryos for the conservation and multiplication of germplasm and the possibility of the establishment of ‘Germplasm Banks’ are discussed.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 69 (1984), S. 93-95 
    ISSN: 1432-2242
    Keywords: Rice ; Protein ; Yield ; Recombinants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Crosses between low and high protein varieties revealed the dominance of low protein over high protein content. The number of desirable segregants with the double combination of high protein and yield were scored in each generation. The increasing frequency of desirable segregants from the F2 to the F3 generation in all the crosses increase the chances of selecting desirable recombinants for propagating improved rice varieties. Hybridisation followed by selection may help in developing varieties with high protein content and superior yield potential.
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  • 7
    ISSN: 1432-2242
    Keywords: Rice ; Repetitive sequences ; Oryza
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Repetitive DNA sequences are useful molecular markers for studying plant genome evolution and species divergence. In this paper, we report the isolation and characterization of four genome-type specific repetitive DNA sequences in the genus Oryza. Sequences specific to the AA, CC, EE or FF genome types are described. These genome-type specific repetitive sequences will be useful in classifying unknown species of wild or domestic rice, and in studying genome evolution at the molecular level. Using an AA genome-specific repetitive DNA sequence (pOs48) as a hybridization probe, considerable differences in its copy number were found among different varieties of Asian-cultivated rice (O. sativa) and other related species within the AA genome type. Thus, the relationship among some of the members of AA genome type can be deduced based on the degree of DNA sequence similarity of this repetitive sequence.
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  • 8
    ISSN: 1432-2242
    Keywords: Biochemical selections ; Lysine ; Mutants ; Proteins ; Rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Endosperm protein mutants in rice may be recovered by biochemical selections with inhibitory levels of lysine and threonine. Among the phenotypes recovered from in vitro selections are lines with increased protein and percent lysine in the protein. This work was designed to identify changes in proteins of rice mutants and to further our understanding of the mechanisms of lysine plus threonine selections in rice. Among the most obvious amino acid changes in mutants was a higher lysine level in all protein solubility fractions and a decrease in tyrosine. Methionine and glutamate are reduced in some protein fractions. However, methionine is significantly higher in the mutant than the control in the glutelin fraction. Several other aspartate pathway amino acids are higher in the mutant than the unselected controls. Separation of proteins in SDS-PAGE gels showed shifts in the protein profiles in the mutants, including a decrease in the major 30 kDa low lysine globulin component, and an increase in several high-molecular-weight components, approximately 60–100 kDa. Increases in the lysine content of proteins of different solubility classes and different proteins within classes are detailed.
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  • 9
    ISSN: 1432-2242
    Keywords: Rice ; Adenine methylation ; Tissue specificity ; Genomic rearrangement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Using ‘A’ and ‘C’ methylation-specific restriction enzymes, namely, MboI, Sau3AI, DpnI, MspI, and HpaII, total rice cv Basmati 370 DNA, repetitive DNAs, and a specific repeat sequence indicated an abundance of adenine methylation. Although cytosine methylation in 5′-CCGG-3′ sequences suggested more CpC methylation than CpG, the ‘C’ methylation in sequence 5′-GATC-3′ was comparatively less than ‘A’ methylation. Furthermore, the presence of adenine methylation was tissue specific; it was predominant in rice shoot DNA as compared to embryo DNA. This pattern was also observed in two other cultivars of rice, i.e., R-24 and Sona, and was again confirmed using a cloned probe of a specific repeat sequence. Besides the changes in adenine methylation, there was also a qualitative change in 5mC from CpG to CpC dinucleotides in these two tissue systems.
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  • 10
    ISSN: 1432-2242
    Keywords: Rice ; Somatic chromosome ; Condensation pattern ; Karyotype ; Discrimination chart
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Somatic rice chromosomes from 30 spreads were analyzed by imaging methods. Morphological characters of each of the 12 rice chromosomes were obtained both by the imaging methods and by visual inspection. The numerical data of relative length, arm ratio, and condensation pattern (CP) were statistically analyzed. The descriptive morphological information obtained was also summarized into numbers of “key characters” or essential short sentences to characterize the traits. The fitness probability or the appearing frequencies of the key character for each of the 30 chromosomes was calculated. Altogether, 118 key characters were extracted to distinguish each rice chromosome. Furthermore, several “discriminants” or critical key characters were determined among the key characters, and a discrimination chart or flowchart to identify all the rice chromosomes was constructed using the discriminants.
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