Use of Petunia inflata as a model for the study of solanaceous type self-incompatibility

Petunia inflata has been used as a model to study solanaceous type self-incompatibility (SI), an RNase-mediated self/non-self recognition mechanism. Pistil proteins that co-segregate with S-alleles (termed S-proteins or S-RNases) were identified, and their role in SI was demonstrated by gain-of-function and loss-of-function experiments. Several lines of evidence strongly suggest that the S-locus contains another gene, termed the pollen S-gene, whose allelic products presumably interact with S-RNases to trigger the SI response. Thus, ultimate understanding of the molecular/biochemical basis of SI requires the identification of the pollen S-gene. A number of approaches that have been used to accomplish this objective are discussed. Differential display and subtractive hybridization have yielded the most promising results: cDNAs corresponding to 13 pollen-expressed genes that lie within 1 cM of the S-RNase gene have been identified. They will be used as markers to identify large S-linked genomic fragments which will then be examined for the presence of the pollen S-gene by plant transformation. (C) 2000 Annals of Botany Company.