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  • 1
    ISSN: 1617-4623
    Keywords: Key words DNA methylation ; Hybrid rice ; Tissue specificity ; Isoschizomers ; PCR amplification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract DNA methylation is known to play an important role in the regulation of gene expression in eukaryotes. In this study, we assessed the extent and pattern of cytosine methylation in the rice genome, using the technique of methylation-sensitive amplified polymorphism (MSAP), which is a modification of the amplified fragment length polymorphism (AFLP) method that makes use of the differential sensitivity of a pair of isoschizomers to cytosine methylation. The tissues assayed included seedlings and flag leaves of an elite rice hybrid, Shanyou 63, and the parental lines Zhenshan 97 and Minghui 63. In all, 1076 fragments, each representing a recognition site cleaved by either or both of the isoschizomers, were amplified using 16 pairs of selective primers. A total of 195 sites were found to be methylated at cytosines in one or both parents, and the two parents showed approximately the same overall degree of methylation (16.3%), as revealed by the incidence of differential digestion by the isoschizomers. Four classes of patterns were identified in a comparative assay of cytosine methylation in the parents and hybrid; increased methylation was detected in the hybrid compared to the parents at some of the recognition sites, while decreased methylation in the hybrid was detected at other sites. A small proportion of the sites was found to be differentially methylated in seedlings and flag leaves; DNA from young seedlings was methylated to a greater extent than that from flag leaves. Almost all of the methylation patterns detected by MSAP could be confirmed by Southern analysis using the isolated amplified fragments as probes. The results clearly demonstrate that the MSAP technique is highly efficient for large-scale detection of cytosine methylation in the rice genome. We believe that the technique can be adapted for use in other plant species.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2242
    Keywords: Key words Common wild rice ; Cultivated rice ; Evolution ; Genetic analysis ; Molecular marker
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Domesticated rice differs from the wild progenitor in large arrays of morphological and physiological traits. The present study was conducted to identify the genetic factors controlling the differences between cultivated rice and its wild progenitor, with the intention to assess the genetic basis of the changes associated with the processes of rice domestication. A total of 19 traits, including seven qualitative and 12 quantitative traits, that are related to domestication were scored in an F2 population from a cross between a variety of the Asian cultivated rice (Oryza sativa) and an accession of the common wild rice (O. rufipogon). Loci controlling the inheritance of these traits were determined by making use of a molecular linkage map consisting of 348 molecular-marker loci (313 RFLPs, 12 SSRs and 23 AFLPs) based on this F2 population. All seven qualitative traits were each controlled by a single Mendelian locus. Analysis of the 12 quantitative traits resolved a total of 44 putative QTLs with an average of 3.7 QTLs per trait. The amount of variation explained by individual QTLs ranged from a low of 6.9% to a high of 59.8%, and many of the QTLs accounted for more than 20% of the variation. Thus, genes of both major and minor effect were involved in the differences between wild and cultivated rice. The results also showed that most of the genetic factors (qualitative or QTLs) controlling the domestication-related traits were concentrated in a few chromosomal blocks. Such a clustered distribution of the genes may provide explanations for the genetic basis of the “domestication syndrome” observed in evolutionary studies and also for the “linkage drag” that occurs in many breeding programs. The information on the genetic basis of some desirable traits possessed by the wild parent may also be useful for facilitating the utilization of these traits in rice-breeding programs.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1572-9788
    Keywords: differential display ; gene expression ; hybrid vigor ; molecular marker heterozygosity ; Oryza sativa L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Using differential display analysis, we assessed the patterns of differential gene expression in hybrids relative to their parents in a diallel cross involving 8 elite rice lines. The analysis revealed several patterns of differential expression including: (1) bands present in one parent and F1 but absent in the other parent, (2) bands observed in both parents but not in the F1, (3) bands occurring in only one parent but not in the F1 or the other parent, and, (4) bands detected only in the F1 but in neither of the parents. Relationships between differential gene expression and heterosis and marker heterozygosity were evaluated using data for RFLPs, SSRs and a number of agronomic characters. The analysis showed that there was very little correlation between patterns of differential expression and the F1 means for all six agronomic traits. Differentially expressed fragments that occurred only in one parent but not in the other parent or in F1 in each of the respective crosses were positively correlated with heterosis and heterozygosity. And conversely, fragments that were detected in F1s but in neither of the respective parents were negatively correlated with heterosis and heterozygosity. The remaining patterns of differential expression were not correlated with heterosis or heterozygosity. The relationships between the patterns of differential expression and heterosis observed in this study were not consistent with expectations based on dominance or overdominance hypotheses.
    Type of Medium: Electronic Resource
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