Project description:Parasitism is a successful life strategy that has evolved independently in several families of Higher Plants. In parasitic plants, nutrients and water are obtained from their hosts through specifically adapted haustoria. The genera Cuscuta and Orobanche represent examples for the two profoundly different groups of parasites, one parasitizing host shoots and the other infecting host roots. In this study, we sequenced and described the overall repertoire of small RNAs (sRNome) from Cuscuta campestris and compared it to an exploratory sRNome from Orobanche aegyptiaca. Because they regulate the genomic information by mechanisms like RNA interference, these sRNomes add important bricks to our understanding of the success of the parasitic lifestyle. We could show that Cuscuta campestris contains a number of novel microRNAs (miRNAs) in addition to a conspicuous retention of miRNAs that are typically lacking in other Solanales, while several typically conserved miRNAs seem to have become obsolete in the parasite. One new miRNA appears to be derived from a horizontal gene transfer event, a process never reported in plants for the acquisition of new miRNA sequences. The exploratory miRNome (exploratory due to the absence of a full genomic sequence for reference) from the root parasitic Orobanche aegyptiaca also revealed a loss of a number of miRNAs compared to established miRNomes of photosynthetic species from the same order. In summary, our study shows for both parasites partly similar evolutionary signatures in the RNA silencing machinery. Our data bear proof for the dynamism of this regulatory mechanism in parasitic plants.
