Plant & Animal Genomes XVI Conference

January 12-16, 2008
Town & Country Convention Center
San Diego, CA

Molecular Characterization Of The Chromosome Segment Governing Apospory In Paspalum notatum (Bahiagrass)

Silvina C Pessino¹ , Juliana Stein¹ , Maricel Podio¹ , María P Rodriguez¹ , Natalia V Laspina¹ , Silvina Felitti^{1, 2} , Eric J Martínez² , Lorena Siena¹ , Camilo L Quarin² , Juan P Ortiz^{1, 2}

¹  Laboratorio de Biología Molecular, Facultad de Ciencias Agrarias, Universidad Nacional de Rosario (UNR), CC14 S2125ZAA Zavalla, Santa Fe, Argentina.

²  Instituto de Botánica del Nordeste (IBONE CONICET), Facultad de Ciencias Agrarias, Universidad Nacional del Nordeste (UNNE), CC 209 3400 Corrientes, Argentina.

Paspalum notatum Flügge is a warm-season forage grass with sexual diploid and apomictic tetraploid races. Natural populations are widely distributed in the New World from Mexico to Argentina and througout the West Indies. The objective of this work was to characterize the genomic region responsible for apospory in the species. A mapping population segregating for apospory was used to develop a full genetic map. The apo-locus was identified as a single non-recombinant genomic region of around 36 Mbp, presenting preferential pairing to one of the homologues. Nine DNA fragments mapping within this region were isolated and sequenced. Several of them corresponded to repetitive elements, while others displayed homology with functional genes or intergenic regions. Methylation-sensitive genomic hybridization blots revealed cytosine methylation at the region. Comparative mapping using RFLP probes showed that the apo-region is syntenic to particular segments of rice chromosomes 2 and 12 and it is probably inverted in the apomictic race. Moreover, cytogenetic evidence of a possible genomic inversion affecting the apomictic genotype was obtained from chromosome-pairing analysis at meiosis. At least two probes derived from genes silenced in apomictic plants mapped linked to the apo region. Our results suggest that apospory in P. notatum is controlled by a complex non-recombinant locus, probably originated from an inversion, including abundant repetitive elements, displaying cytosine methylation and possibly silenced.