Genetic, epigenetic and transcriptional changes associated to ploidy and diplospory in

CERVIGNI, G.; SELVA, J.P.; MECCHIA, M.; OCHOGAVIA A; PANIEGO, N.; CARDONE, S.; POLCI, P.; FELITTI, S.; MARTELOTTO L; DIAZ, M; ZAPPACOSTA, D.; MEIER, M.; VOIGT, P.W.; SPANGENBERG, G.; PESSINO, S.; ECHENIQUE, V.

San Diego, California, US

Congreso; XVI Plant and Animal Genome Conference; 2008

Genetic, epigenetic and transcriptional changes were analyzed in an euploid series of E. curvula (pseudogamous diplosporous grass) obtained after a tetraploid dihaploidization procedure followed by chromosome re-doubling with colchicine. Considerable levels of genome polymorphisms were detected between lines, showing markers (AFLPs, RAPDs) with a revertant behavior following the changes of ploidy. This suggests that genome alterations were specific and conferred genetic structures characteristic of a given ploidy level. Polymorphic revertant sequences involved mostly non-coding regions, although some of them displayed sequence homology to known genes. Changes also involved alterations in cytosine methylation patterns, affecting mainly coding regions. A comparative expression analysis based on ESTs and differential display (DD) showed that from 8,884 unigenes (inflorescence-derived libraries), 112 (1.26%) had significant differential expression in individuals with different ploidy level and/or reproductive mode. Independent comparisons between plants with different reproductive mode (same ploidy) or different ploidy level (same reproductive mode) allowed the identification of genes modulated in response to diplosporous development or polyploidization, respectively. A group of 50 genes were differencially expressed between the 4x sex and the other plant lines (2x sex, 4x apo) that exhibited highly similar expression patterns. DD analysis showed that the 4x apo and 4x sex gene expression profiles were more related and different from the 2x sex one, but confirmed the expression of this particular group of genes. As a difference of what happens with the 4x sex plant, the activation/silencing of these genes fail in the 4x diplosporous plant. Diplospory could be the consequence of this failure.