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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Sexual plant reproduction 10 (1997), S. 101-106 
    ISSN: 1432-2145
    Keywords: Key words Pollen ; Pollen competition ; Pollen performance ; Microgametophyte
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  We examined the influence of pollen competitive environment on pollen performance in Mirabilis jalapa. We used the number of pollen grains and the number of pollen tubes per pistil as measures of pollen competition. Pollen germination, pollen tube penetration into the style, and pollen tube growth rates were used as measures of pollen performance. All three measures of pollen performance were affected by the competitive environment. Pollen germination was greatest at intermediate pollen load sizes. The percentage of germinated pollen grains that penetrated the stigma and grew into the style decreased with pollen load size. Pollen tube growth rate in the style was greater and more variable with larger numbers of pollen tubes in the style. Controlling for the degree of selection at the stigma indicated that pollen-pollen or pollen-style interactions were the likely causes of increased growth rates.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1617-4623
    Keywords: Prolidase ; Metalloprotease ; Lactobacillus delbrueckii subsp. lactis ; Nucleotide sequence analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract From a genomic library of Lactobacillus delbrueckii subsp. lactis (DSM7290) DNA, in the low-copy-number vector pLG339, a recombinant clone was selected, which complemented a mutation in the prolidase gene (pepQ) of Escherichia coli UK173. Nucleotide sequence analysis revealed an open reading frame of 1104 nucleotides corresponding to a protein of 368 amino acids with a calculated pI of 4.64 and a molecular mass of 41087 Da. The start site of pepQ transcription was determined by primer extension analysis with mRNA prepared from L. delbrueckii. Based on homology of the gene product to various peptidases and on the substrate specificity determined, the peptidase was designated PepQ. The influence of various protease inhibitors and cations on peptidase activity indicated that PepQ is a metalloprotease. The absence of a membrane-spanning domain and a signal peptide sequence argues for a cytoplasmic localization of the enzyme.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    BioEssays 17 (1995), S. 959-965 
    ISSN: 0265-9247
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In the yeast Saccharomyces cerevisiae three positive transcriptional control elements are activated by stress conditions: heat shock elements (HSEs), stress response elements (STREs) and AP-1 responsive elements (AREs). HSEs bind heat shock transcription factor (HSF), which is activated by stress conditions causing accumulation of abnormal proteins. STREs mediate transcriptional activation by multiple stress conditions. They are controlled by high osmolarity via the HOG signal pathway, which comprises a MAP kinase module and a two-component system homologous to prokaryotic signal transducers. AREs bind the transcription factor Yap1p. The three types of control elements seem to have overlapping, but distinct functions. Some stress proteins encoded by HSE-regulated genes are necessary for growth of yeast under moderate stress, products of STRE-activated genes appear to be important for survival under severe stress and ARE-controlled genes may mainly function during oxidative stress and in the response to toxic conditions, such as caused by heavy metal ions.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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