St. John\u2019s wort (Hypericum perforatum L.) is a medicinal plant that produces important
metabolites with antidepressant and anticancer activities. Beside the pharmaceutical interest,
recently gained information has shown that H. perforatum is also an attractive model system for the
study of aposporous apomixis, that is a reproductive strategy, which, unlike sexual reproduction,
permits the inheritance of the maternal genome over generations without genetic recombination
events. This asexual mode of seed formation is believed to be a trait with enormous economic and
social potential in agriculture. Its innovative use in this area relies upon the idea that indefinitely
fixing highly complex genotypes, including hybrid cultivars, through apomixis would have
tremendous advantages in plant breeding, biomass and seed production. During the last decades, the
understanding of the molecular basis of apomixis in this species has been complicated by the lack of
biological data, e.g. genomic or even transcriptomic sequences. The aim of our research project was
the sequencing, annotation and comparative investigation of the H. perforatum flower
transcriptome, as critical steps toward a better understanding of the genetic control of aposporic and
sexual reproduction in the facultative apomict H. perforatum. To this end, next generation
sequencing technologies have been used to sequence the flower transcriptomes of obligate sexual
and unrelated apomictic H. perforatum genotypes. This approach has enabled the assembly and
annotation of large cDNA repositories and their exploitation to design a custom array to be used in
flower expression studies. Global gene expression analysis of H. perforatum was initially
performed on ovaries collected from sexual and aposporic plant accessions for the purpose of
identifying genes and processes potentially associated with apomixis in this model species. Overall,
across two selected developmental stages, 224 and 973 unigenes were found to be significantly upand down-regulated. Ontological annotation of differentially expressed genes indicated that terms
related to cell cycle, single-organism cellular process DNA (cytosine-5-)-methyltransferase activity,
among others, were significantly enriched. In a following step, a laser-capture microdissection
approach was adopted in combination the RNA-seq technology with the aim of identifying genes
differentially expressed in the ovule cell types primarily involved in the differentiation of the
megaspore mother cells and aposporous initials. On the whole, our data suggest that phenotypic
expression of apospory is concomitant with the modulation of key genes involved in the sexual
reproductive pathway and the responsive to hormonal stimuli. Annotation of all identified flower
transcripts as well as their qualitative and quantitative expression data will be presented and
critically discussed as they prove a far better understanding of molecular bases of pistil
development, embyo sac and egg cell formation in sexual and apomictic H. perforatum