Estimation of frequencies, patterns and variation of cytosine methylation in diploid and tetraploid races Paspalum notatum

RODRIGUEZ MP; CERVIGNI, GDL; QUARIN CL; ORTIZ JPA

Buenos Aires

Simposio; The 6th International Symposium of the molecular breeding of forage and turf; 2010

Molecular Breeding of Forage and Turf International Committee

Paspalum notatum Flugge is a warm season forage grass with mainly diploid (2n=2x=20) and autotetraploid (2n=4x=40) representatives. Diploid races reproduce sexually and require crosspollination due to a self-incompatible mating system, while tetraploids reproduce by aposporous apomixis. Polyploidy has considerable effects on duplicate gene expression, including silencing and up- or down regulation of one of the duplicated genes. These changes can arise with the onset of polyploidization or within several generations after polyploid formation and they can have epigenetic causal factors. MSAP (methylation-sensitive amplified polymorphism) is a simple, efficient and reliable technique for the detection of methylation status a genome form a wide perspective. MSAP introduces a pair of methylation-sensitive restriction isoschizomers (M,spl and Hpall) as frequent cut enzymes in the standard AFLP protocol. The objective of this work was to carry out a general survey of the frequencies, patterns and variation of cytosine methylation in diploid and tetraploid races of P. notatum and identify changes associated with the tetraploidization in the species. MSAP were used for analyzing 4 diploids and 4 tetraploid genotypes. Proportion 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 epigentic similarity showed that tetraploids were more diverse than diploids, although equivalent values were obtained when similarity was estimated with methylation-insensitive markers. A significant correlation was detected between epigenetic and non-epigenetic variation in tetraploids. Clustering analysis of epigenetic similarities including all genotypes showed that the four diploids and one tetraploid grouped together suggesting a common epigenetic structure. Sequences several MSAP markers exhibited homologies with protein-coding, transposon/retrotransposon elements and non-coding sequences.