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41.
Ana Carvalho Margarida Delgado Augusta Barão Márcia Frescatada Edna Ribeiro Craig S. Pikaard Wanda Viegas Nuno Neves 《Sexual plant reproduction》2010,23(1):29-37
Variation in chromosome number due to polyploidy can seriously compromise meiotic stability. In autopolyploids, the presence
of more than two homologous chromosomes may result in complex pairing patterns and subsequent anomalous chromosome segregation.
In this context, chromocenter, centromeric, telomeric and ribosomal DNA locus topology and DNA methylation patterns were investigated
in the natural autotetraploid, Arabidopsis arenosa. The data show that homologous chromosome recognition and association initiates at telomeric domains in premeiotic interphase,
followed by quadrivalent pairing of ribosomal 45S RNA gene loci (known as NORs) at leptotene. On the other hand, centromeric
regions at early leptotene show pairwise associations rather than associations in fours. These pairwise associations are maintained
throughout prophase I, and therefore likely to be related to the diploid-like behavior of A. arenosa chromosomes at metaphase I, where only bivalents are observed. In anthers, both cells at somatic interphase as well as at
premeiotic interphase show 5-methylcytosine (5-mC) dispersed throughout the nucleus, contrasting with a preferential co-localization
with chromocenters observed in vegetative nuclei. These results show for the first time that nuclear distribution patterns
of 5-mC are simultaneously reshuffled in meiocytes and anther somatic cells. During prophase I, 5-mC is detected in extended
chromatin fibers and chromocenters but interestingly is excluded from the NORs what correlates with the pairing pattern. 相似文献
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Pandey R Müller A Napoli CA Selinger DA Pikaard CS Richards EJ Bender J Mount DW Jorgensen RA 《Nucleic acids research》2002,30(23):5036-5055
Sequence similarity and profile searching tools were used to analyze the genome sequences of Arabidopsis thaliana, Saccharomyces cerevisiae, Schizosaccharomyces pombe, Caenorhabditis elegans and Drosophila melanogaster for genes encoding three families of histone deacetylase (HDAC) proteins and three families of histone acetyltransferase (HAT) proteins. Plants, animals and fungi were found to have a single member of each of three subfamilies of the GNAT family of HATs, suggesting conservation of these functions. However, major differences were found with respect to sizes of gene families and multi-domain protein structures within other families of HATs and HDACs, indicating substantial evolutionary diversification. Phylogenetic analysis identified a new class of HDACs within the RPD3/HDA1 family that is represented only in plants and animals. A similar analysis of the plant-specific HD2 family of HDACs suggests a duplication event early in dicot evolution, followed by further diversification in the lineage leading to Arabidopsis. Of three major classes of SIR2-type HDACs that are found in animals, fungi have representatives only in one class, whereas plants have representatives only in the other two. Plants possess five CREB-binding protein (CBP)-type HATs compared with one to two in animals and none in fungi. Domain and phylogenetic analyses of the CBP family proteins showed that this family has evolved three distinct types of CBPs in plants. The domain architecture of CBP and TAF(II)250 families of HATs show significant differences between plants and animals, most notably with respect to bromodomain occurrence and their number. Bromodomain-containing proteins in Arabidopsis differ strikingly from animal bromodomain proteins with respect to the numbers of bromodomains and the other types of domains that are present. The substantial diversification of HATs and HDACs that has occurred since the divergence of plants, animals and fungi suggests a surprising degree of evolutionary plasticity and functional diversification in these core chromatin components. 相似文献
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Arabidopsis histone deacetylase HDA6 is required for maintenance of transcriptional gene silencing and determines nuclear organization of rDNA repeats 下载免费PDF全文
48.
Joe H. Cherry Lauren Bishop Nancy Leopold Craig Pikaard Paul M. Hasegawa 《Phytochemistry》1984,23(10):2183-2186
Fatty acid deposition in developing soybean seeds of high- and low-linolenic acid cultivars show a great deal of similarity. In all cultivars, the greatest change in fatty acid content occurs during the first half of seed formation. The amount of linolenic acid is highest during the very early stage of seed formation and the relative amount decreases thereafter. Linolenic acid content in mature soybean seed is inversely proportional to that of oleic acid. 相似文献
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