Flower Transcriptomics for Uncovering Genes Related to Plant Reproduction in the Facultative Apomict Hypericum perforatum L.

St. John’s wort (Hypericum perforatum L.) is a medicinal plant species and also an attractive model system for the study of apomixis, despite a lack of genomic and transcriptomic data. We sequenced and annotated its flower transcriptome to provide critical knowledge toward a better understanding of the genetic control of aposporic and sexual reproduction. We used Roche 454 technology to sequence the entire flower transcriptome of single flower parts collected from three apomictic and two sexual genotypes, which enabled us to investigate the coding and non-coding RNA fractions of the flower transcriptome and identify RNAs that are likely exclusive to single flower organs or reproductive strategies. The protein-coding sequences of the flower RNAs were annotated using Gene Ontology terms in order to identify major biological processes and molecular functions involved in flower development and plant reproduction. Starting from this dataset, we were able to recover and annotate a large number of transcripts related to meiosis, gametophyte and gamete formation, and embryogenesis. We also developed and used Microarray analysis for studying gene expression in reproductive organs at two different developmental stages (apo-meiosis vs. gametogenesis) from replicated genotypes with antagonist mode of reproduction with the aim of uncovering genes or RNAs that may differentiate and/or regulate the sexual and apomictic reproductive pathways in this species. In particular, genes that are exclusively or preferentially expressed in sexual or apomictic genotypes and developmental stages were identified. Overall flower transcriptome data will presented and critically discussed.