Transcriptomic analysis of floral incompatible and compatible reactions in Prunus dulcis

Almond exhibits self-incompatibility of the gametophytic type, which is controlled by the S-locus, a single polymorphic locus containing the pistil S-RNase gene and the pollen SFB gene. In addition to these determinant genes, recent studies have proposed the existence of non-S components involved in the incompatibility reaction. A few transcriptomic studies have tried to identify these other factors of the gametophytic self-incompatibility system in Citrus, Prunus and Solanum species using comparative transcriptomics of pistils. However, to date, similar studies have not been reported in almond. In this work, we aimed to capture all the molecular events induced by incompatible and compatible reactions in almond. For this, transcriptome analyses of un-pollinated pistils and of compatible and incompatible pollinations using high-throughput RNA sequencing technologies were conducted. For each sample, more than 32% of 100-nucleotide paired-end Illumina reads were aligned to the peach reference genome. Among these unigenes, 28,702 transcript sequences showed a hit against the NCBI databases and 1,358 transcripts appear as differentially expressed in the different conditions. The differentially expressed genes were GO-annotated, allowing the classification in different groups of the transcripts implicated in the (in)compatibility response. The results of gene expression profiles were validated using RT-qPCR. This study illustrates the dynamics of the gametophytic self-incompatibility system in almond according to differences in the expression patterns of genes.