Transcriptome Analysis of Stigmas of Vicia faba L. Flowers

Pollination in angiosperms depends on a complex communication between pollen grains and stigmas, classified as wet or dry, depending on the presence or absence of secretions at the stigma surface, respectively. In species with wet stigma, the cuticle is disrupted and the presence of exudates is indicative of their receptivity. Most stigma studies are focused on few species and families, many of them with self-incompatibility systems. However, there is scarce knowledge about the stigma composition in Fabaceae, the third angiosperm family, whose stigmas have been classified as semidry. Here we report the first transcriptome profiling and DEGs of Vicia faba L. styles and stigmas from autofertile (flowers able to self-fertilize in absence of manipulation whose exudate is released spontaneously) and autosterile (flowers that need to be manipulated to break the cuticle and release the exudates to be receptive) inbred lines. From the 76,269 contigs obtained from the de novo assembly, only 45,1% of the sequences were annotated with at least one GO term. A total of 115,920, 75,489 and 70,801 annotations were assigned to Biological Process (BP), Cellular Component (CC) and Molecular Function (MF) categories, respectively and 5,918 differentially expressed genes (DEGs) were identified between the autofertile and the autosterile lines. Among the most enriched metabolic pathways in the DEGs subset were those related with aminoacid biosynthesis, terpenoid metabolism or signal transduction. Some DEGs have been related with previous QTLs identified for autofertility traits, and their putative functions are discussed. Results derived from this work provides an important transcriptomic reference for style-stigma processes to aid understanding of the molecular mechanisms involved in faba bean fertilization.