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  • 1
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The heterophyllous macrophyte waterchestnut (Trapa natans L.) produces floating and submerged leaves which are strikingly different in morphology. In the present work, we compared, through cytological, cytochemical and immunocytochemical analyses, the nuclear features of the shoot meristem in floating and submerged buds that produce the different leaves. The occurrence of DNA polymorphism in the two types of leaves was studied by using the random amplified polymorphic DNA (RAPD) approach. The light microscope study of chromatin organization revealed an articulate structure of the nuclei, with prominent chromocentres in both floating and submerged buds. However, the meristematic nuclei of floating buds, as compared to those of submerged buds, displayed peculiar features which seem to be related to a higher proportion of A-T-ricn sequences and a higher level of DNA methylation of the nuclear genome. Moreover, RAPD analysis showed polymorphism between the genomic DNAs of floating and submerged leaves. These results show that organs of an individual plant living in different environmental conditions undergo changes in genome organization which may predispose those organs to function more effectively in different environments.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1617-4623
    Keywords: Key wordsPrunus persica ; Ribosomal proteins ; Gene expression ; Gene regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract RT-PCR was performed on peach (Prunus persica [L.] Batsch) RNA to isolate cDNAs corresponding to transcripts which are differentially expressed in leaves borne on basal and apical shoots. A gene was identified which was more highly expressed in the leaves of basal shoots, and codes for the cytoplasmic protein S28 present in the small ribosomal subunit. The 5′ leader regions of RPS28 mRNAs were found to harbour 8–11 pyrimidine tracts, which suggested similarities to regulatory stretches that control the translation of mRNAs for ribosomal proteins in animals. The peach S28 is encoded by two intron-containing genes, which are both transcribed in mitotically active tissues such as developing leaves and roots. In situ hybridisation to shoot vegetative apices and the measurement of nucleus/nucleolus ratios indicated that RPS28 expression was confined to areas undergoing active cell division. The mature RPS28 mRNA was detected as a single species in actively dividing tissues such as apical tips, developing leaves, vegetative buds, stamens, developing fruits and roots. In contrast, accumulation of a precursor RNA, in the presence of the mature product, was found in fully expanded leaves and subtending stems, while only the precursor species was detected in several late-stage tissues. This phenomenon suggested that expression of the mature RNA is controlled at the level of splicing and turnover of the precursor RNA. This is similar to the mode of regulation of ribosomal protein genes in animals.
    Type of Medium: Electronic Resource
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