Transgenerational inheritance of epigenetic regulation by Unstable factor for orange1 in maize.

Open Access
Author:
Abu Bakar, Nur Suhada
Graduate Program:
Agronomy
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
May 08, 2013
Committee Members:
  • Surinder Chopra, Thesis Advisor
  • Majid R Foolad, Thesis Advisor
  • Dawn S Luthe, Thesis Advisor
Keywords:
  • epigenetics
  • DNA methylation
  • inheritance
Abstract:
Epigenetics is the study of heritable changes in gene expression or cellular phenotype that are attributable to mechanisms other than changes in DNA sequence. In plants, epigenetic regulation plays a key role in various biological processes such as paramutation, genomic imprinting, and gene silencing. Although numerous studies have been done to elucidate the underlying mechanism behind epigenetic regulation, many questions are yet to be answered. In this study, the maize pericarp color1 (p1) gene is used as a reporter to study the nature of epigenetic inheritance of stable tissue-specific gene expression. An allele of p1, P1-wr was used as a phenotypic marker to investigate the transgenerational inheritance of Unstable factor for orange1 (Ufo1-1)-induced changes in maize. Ufo1-1 activates p1 expression and thus phlobaphenes are ectopically accumulated throughout the plant body indicating loss of tissue-specificity of p1 expression. Previous study has shown that Ufo1-1-induced pigmentation phenotypes are only observed in a subset of P1-wr; Ufo1-1 plants. Interestingly, within this subset, pigmentation level is highly variable. Also, it has been shown that this increased pigmentation is associated with changes of DNA methylation pattern in the P1-wr distal enhancer and intron sequences. Moreover, the increased pigmentation phenotypes in the backcross population are accompanied by progressive loss of P1-wr methylation from one generation to the next. Thus, the objective of this study was to investigate the inheritance of Ufo1-1 through genotyping using linked markers. This information was then compared to the Ufo1-1-induced phenotypes to verify the epigenetic regulation of P1-wr by Ufo1-1. The second objective of this study was to establish a qRT-PCR based assay to investigate DNA methylation level at p1 in different genotypes of P1-wr; Ufo1-1 plants. The relative methylation levels provided better understanding of the correlation between the range of pericarp pigmentation in P1-wr; Ufo1-1 plants and their respective DNA methylation states at p1.