Identification of candidate genes involved in the self incompatibility response in clementine

Compared to what is known in model species, reproductive biology in citrus is still poorly understood. Although in recent years several efforts have been made to study pollen-pistil interaction and self-incompatibility, little information is available about the molecular mechanisms regulating these processes. Here we report the identification of candidate genes involved in pollen-pistil interaction and selfincompatibility in clementine (Citrus clementina Hort. ex Tan.). These genes have been identified comparing the transcriptomes of laser-microdissected stylar canal cells isolated from two clementine genotypes differing in their self-incompatibility response ('Comune', self-incompatible; and 'Monreal', a self-compatible mutation of 'Comune'). Transcriptome profiling was performed using the Affymetrix Citrus GeneChip representing up to 33,000 citrus transcripts. Among them, only 10 genes resulted over represented in 'Comune' stylar canals and 7 genes in 'Monreal' ones. The results of microarray hybridizations were validated using real time quantitative RT-PCR. Many of the differentially expressed genes are not functionally annotated in citrus or other plant species. The results suggest that the differential regulation of few specific transcripts is probably related to the breakdown of self-incompatibility in 'Monreal'.