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DNA METHYLATION PROFILES DIFFER BETWEEN JUVENILE AND ADULT PHASE LEAVES OF CRAB APPLE (MALUS MICROMALUS) SEEDLING TREE

ISHFAQ A. HAFIZ, NADEEM A. ABBASI, TOUQEER AHMAD AND AZHAR HUSSAIN

Abstract: Cytosine methylation has been implicated in regulation of gene expression, genomic imprinting and chromatin remodeling, resulting both in temporal and developmental regulation. In the present study methylation-sensitive amplification polymorphism (MSAP) associated with the transition from juvenile to adult phase in Malus micromalus was explored using a pair of restriction endo-nucleases EcoR II, Bst0.The extracted genomic DNA from juvenile and adult phase leaves of the seedling tree was digested with EcoR II and Bst0I, and amplified using eight primers. In total 77 bands were amplified. Post amplification digestion of these bands with EcoR II or Bst0 I revealed 32 bands containing CC(A/T)GG. Six bands were absent in amplified profiles from juvenile phase digested DNA, appeared in amplified products from digested adult phase DNA, indicating de novo methylation at CC(A/T)GG site. Five bands disappeared in Adult phase while these bands were present in Juvenile phase DNA amplified profiles, revealing presence of restriction site without methylation in adult phase. These results are suggestive that demethylation may have occurred in adult phase. Seventeen motifs of DNA methylation at CC(A/T)GG remaining similar in both phases seem to have been maintained from basal to crown part of the seedling tree. Amplified profiles produced from restricted DNA from both phases showed polymorphism due to differential methylation.

Department of Horticulture, University of Arid Agriculture Rawalpindi, Pakistan.