Genomic changes at the early stage of somatic hybridization.

A broad spectrum of genetic and epigenetic changes is induced by wide hybridization and subsequent polyploidization, but the timing of these events remains obscure because early hybrid cells are very difficult to harvest and analyze. Here, we used both cytological and genetic marker approaches to analyze the constitution of very young somatic hybrid cells between japonica rice (Oryza sativa L. subsp japonica) and indica rice (Oryza sativa L. subsp indica) and between japonica rice and bread wheat (Triticum aestivum L.). Chromatin elimination, simple sequence repeats, and retrotransposon profile deletions were already apparent within six days of the fusion event. The evidence we have presented suggests that genomic changes induced by genomic shock occur soon after the formation of hybrid cells.