SRP308526 PRJNA705387 RNase-based Self-incompatibility in Cacti Approximately one half of all flowering plants express genetically-based physiological mechanisms that prevent self-fertilization. One such mechanism, termed RNase-based self-incompatibility, employs ribonucleases as the pistil-component. Although it is widespread, it has only been characterized in a handful of distantly related families, partly due to the difficulties presented by life history traits of many plants, which complicate genetic research. Many species in the cactus family are known to express self-incompatibility but the underlying mechanisms remain unknown. We demonstrate the utility of a candidate-based RNA-seq approach, combined with some unusual features of self-incompatibility-causing genes, which we use to uncover the genetic basis of the underlying mechanisms. Specifically, we assemble transcriptomes from Schlumbergera truncata (crab cactus or false Christmas cactus), and interrogate them for tissue-specific expression of candidate genes, their structural characteristics, correlation with expressed phenotype(s), and phylogenetic placement. The results are consistent with operation of the RNase-based self-incompatibility mechanism in Cactaceae. The finding yields additional evidence for ancestry of this mechanism in nearly all eudicots and a clear path to better practices for conservation of one of the most charismatic plant families. The finding yields additional evidence that the ancestor of nearly all eudicots possessed RNase-based self-incompatibility, as well as a clear path to better conservation practices for one of the most charismatic plant families. pubmed 34101188