Methyla sensitive amplicon polymorphism and molecular basis of heterosis in rice Oryza sativa L

Abstract

Understanding the heterosis will help enhance the efficiency of hybrid breeding. Of the newlinevarious approaches used at the molecular level to understand heterosis, study on the newlineregulatory mechanisms viz., DNA methylation has received considerable attention. The newlineobjective of this study was to study the differential methylation levels, patterns and directions newlineamong the parents and hybrids in relation to heterosis. newlineThe experimental material consisted of four experimental hybrids and four commercial newlinehybrids and their parents. The study on over all methylation level showed that the 30.31 per newlinecent of cytosines in the rice genome were methylated. Further, the analysis revealed the newlinepresence of variability for methylation level in different genotypes of rice which may contribute newlineto phenotypic variability among the genotypes. newlineThe present study identified three major classes of patterns of cytosine methylation newlinecharacterized by (1) the difference in banding pattern between the parents, (2) more newlinemethylated sites (hypermethylated) in hybrid and (3) less methylated sites (demethylated) in newlinethe hybrid. It was found that demethylation is the predominant methylation event to occur in newlinethe hybrids. These events may lead to hybrid specific expression of certain genes involved in newlinethe manifestation of heterosis. newlineCorrelation analysis revealed that hypermethylation and total methylation level of hybrid newlinewas significantly negatively associated with yield and yield heterosis. Cloning and sequencing newlineof differentially methylated fragments identified five of the ten methylated sequences as gene newlinesequences of some proteins. newlineIt was observed that in the early stages of hybrid, the demethylation was in a higher newlinefrequency compared to hypermethylation. Thus, decreasing levels of cytosine methylation as newlinethe hybrid grows, coupled with higher rate of demethylation events occurring during the early newlinestages, suggests the possible role of DNA methylation to modulate the hybrid specific gene newlineexpression/suppression in a stage dependant, tissue specific manner to m