PSI Atlas is a comprehensive knowledgebase of plant self-incompatibility (SI). SI is an important genetic mechanism in angiosperms that prevents inbreeding and promotes outcrossing. In eudicots, SI is typically regulated by a single S-locus with diverse S-haplotypes, while in grasses, it is controlled by two separate S and Z loci. Given the significant variation in the molecular mechanisms underlying SI systems across different families, they can be further divided into eight types. These include gametophytic type-1 SI, controlled by the pistil S S-RNase and pollen S SLF, found in Plantaginaceae, Solanaceae, Rosaceae, and Rutaceae; sporophytic type-2 of Brassicaceae, governed by SRK and SP11/SCR; gametophytic type-3 of Papaver rhoeas, determined by PrsS and PrpS; heterostyly type-4 of Primulaceae, defined by a hemizygous S-locus encoding CYP, GLO2, KFB, CCM, and PUM; heterostyly type-5 of Turneraceae, controlled by SPH1, YUC6, and BAHD; gametophytic type-6 of Poaceae, by HPS10-S/Z and DUF247I/II-S/Z; heterostyly type-7 of Linaceae, by TSS1 and WDR44; and type-8 of Oleaceae, by GA2ox.
    PSIA offers an extensive compilation of plant SI, including genomic resources for assembled SI species, the origins and evolution of S genes, and the molecular mechanisms of the eight known SI types. In our most recent release, we have obtained more than 500 genome assemblies across 469 SI species. We have also collected 1275 nucleotide and 1130 protein sequence accessions of S genes from public databases, with a total of 3700 S genes manually identified and curated. PSIA not only thoroughly explores the S-locus information of the assembled SI species but also enables users to efficiently browse, perform BLAST searches, analyze, and download S genes. Additionally, PSIA acts as a comprehensive platform for comparative genomic studies of S-loci, aiding in the exploration of the dynamic processes involved in the origin, loss, and regain of SI. Consequently, PSIA is poised to significantly enhance our understanding of angiosperm SI and offer new perspectives on plant mating systems.

Origin and Evolution of SI