Evolution of transcriptomes in early generation hybrids of the apomictic Ranunculus auricomus complex

Hybridisation in plants may cause a shift from sexual to asexual seed formation (apomixis). In-deed, natural apomictic plants are usually hybrids, but it is still unclear how hybridization could trigger the shift to apomixis. Genome evolution of older apomictic lineages is influenced by di-verse processes like polyploidy, mutation accumulation, and allelic sequence divergence. To disentangle effects of hybridization from these other factors, we analysed transcriptomes of flowering buds from artificially produced, diploid F2 hybrids of the Ranunculus auricomus com-plex. The hybrids exhibited unreduced embryo sac formation (apospory) as one important component of apomixis whereas their parental species are sexual. We revealed 2,916 annotated single-copy genes that were mostly under purifying selection according to dN/dS ratios. How-ever, pairwise comparisons revealed after rigorous filtering 79 genes under diversifying selec-tion between hybrids and parents, whereby gene annotation assigned ten of them to reproduc-tive processes. Four genes belong to the meiosis-sporogenesis phase (ASY1, APC1, MSP1, and XRI1) and are, according to literature records, candidate genes for apospory. We conclude that hybridisation could combine novel (or existing) mutations in key developmental genes in cer-tain hybrid lineages, and establish together with altered gene expression profiles a heritable regulatory mechanism for aposporous development.