11-Maydica Kovacevic - ABSTRACT - Epigenetic phenomena and...

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Unformatted text preview: ABSTRACT - Epigenetic phenomena and particularly DNA methylation play a significant role in regulating gene expression in eukaryotes. Restriction Landmark Genomic Scanning (RLGS), which in a single assay displays the methylation status of more than a thousand genomic re- gions containing Not I recognition sites, was used to evalu- ate the status of global methylation in maize parental in- bred lines and hybrids, and the effects of density induced stress on the methylation status of a hybrid selected for its stability of performance. Examining the RLGS patterns of two S 5 inbreds it was determined that they differed in to- tal DNA methylation by 20%. Their F 1 hybrid displayed methylation patterns similar to its parents for the majority of the detected spots, although some Not I landmarks were genotype-specific. Comparison of the RLGS profile of a stable F 1 hybrid grown under low and high planting density (density induced stress) showed that its methyla- tion pattern was influenced by conditions of growth. However, density induced stress caused only a slight in- crease in the copy number of methylated fragments, indi- cating that the stable hybrid could be resistant to stress- induced methylation changes. Our results suggest that dif- ferent levels of global genomic DNA methylation might be related to the field performance potential of specific maize inbred lines and hybrids, and resistance of the hy- brids to methylation changes induced by density stress could be part of hybrid superiority and stability of perfor- mance facing different stress conditions. KEY WORDS: Heterosis; Maize; Methylation; RLGS; Stress. INTRODUCTION Epigenetic phenomena and particularly DNA methylation are receiving much attention and com- plement classical genetics in many fields including molecular and developmental biology, epidemiolo- gy, cancer biology, breeding and evolution. DNA methylation, catalyzed by DNA methyltransferases (F INNEGAN and K OVAC , 2000), is observed in such distinct organisms as bacteria and humans. The most abundant methylated base in eukaryotes, 5- methylcytosine, acts together with other chromatin modifications to maintain the silent state of some genomic regions, enabling the transcription only of genes that are required for cell activity (R AZIN , 1998). Consequently, changes in DNA methylation patterns are hallmarks of development, evolutionary adaptation, defense and disease in organisms. For example, in plants altered genomic cytosine methy- lation has been correlated with processes as differ- ent as gametic imprinting, paramutation, phenotypic variation, stress responses, and changes in the activ- ity of transposable elements and transgenes in transgenic plants (F INNEGAN et al ., 2000)....
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This note was uploaded on 09/13/2010 for the course DGPB 024e taught by Professor Alexiospolidoros during the Spring '10 term at Aristotle University of Thessaloniki.

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11-Maydica Kovacevic - ABSTRACT - Epigenetic phenomena and...

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