CONICET | Buscador de Institutos y Recursos Humanos

Abstract: The objective of this work was to carry out a general survey of the frequencies, patterns and variation of cytosine methylation in 4 diploid (sexual) and 4 tetraploid (2 apomictic and 2 sexual) genotypes of P. notatum, by using Methylation-Sensitive Amplification Polymorphisms (MSAP). The proportions of methylated CCGG sites ranged from 38.58 % to 42.51 % and 27.54 % to 44.74 % in diploids and tetraploids, respectively. Non-significant differences were found between the average proportions of methylation among cytotypes. Analysis of epigenetic similarity showed that tetraploids were more diverse than diploids, although equivalent values were produced when similarity was estimated with methylation-insensitive markers. A significant correlation was detected between epigenetic and non-epigenetic variation in tetraploids, but not in diploids. A dendrogram of epigenetic similarities including all genotypes showed that the four diploids and one tetraploid of experimental origin clustered together in single group, while the rest of the tetraploids spread around both sides of it. An equivalent MSAPs analysis performed on the diploid cytotype C4-2x and its autotetraploid derivative C4-4x, showed that both plants were highly similar at both the genetic and epigenetic level, although methylation polymorphisms associated with the ploidy were detected. Sequences of several MSAP markers showed homologies with protein-coding, transposon/retrotransposon elements and non-coding sequences. The results obtained in this work indicated that although proportion of methylated sites in diploids and tetraploids were comparable, the pattern and variation of the methylation sites differed among cytotypes. Moreover, it was not possible establish a direct relationship between the methylation landscape and the mode of reproduction. MSAP analysis carried out with the genotypes C4-2x and C4-4x showed that new epialleles are generated after the tetraploidization in the species.