Analysis of Global DNA Methylation in Irradiated Fig Selections

Abstract

Fruits from fig tree (Ficus carica L.) are economically important worldwide, and rank among the top 20 fruits exported by Brazil. However, due to particular features in its floral structure, classical plant breeding procedures that involve hybridization are not possible. Thus, genetic improvement of figs by using mutagens is an important line of research. In this study, five fig selections based on their interesting agronomic features were used. Genetic modifications associated with mutations were not detected by molecular markers. Therefore, it was suggested that certain phenotypes could have resulted from epigenetic modifications. The best characterized epigenetic modification is DNA methylation, which can switch genes on or off by acting as a signal. After epigenetic polymorphisms were identified by methylation sensitive amplified polymorphism (MSAP) molecular markers, we quantified the level of DNA methylation in fig selections irradiated with gamma rays and compared it to levels in the commercial cultivar "Roxo-de-Valinhos." This was achieved by analyzing the global methylation using an Imprint Methylated DNA Quantification kit. The results showed that there were significant differences in global methylation following different treatments, indicating that irradiation was an abiotic factor that could alter the epigenome of plants. Since the material used as a control was also found to be methylated, demethylation of the polymorphic genomic material might account for the phenotypic variations observed among different treatment groups. These results suggest that irradiation is an external factor that is capable of altering epigenetic patterns.