Pistil non-S-specific self-incompatibility factor HT-B is tightly linked to the HT-like gene HTL in Petunia

Self/non-self discrimination between pollen and pistil in gametophytic self-incompatibility (GSI) system of Solanaceae is controlled by a single S locus with multiple haplotypes. However, genetic analyses have shown that factors outside the S locus are also required for GSI to take place. So far, a limited number of such non-S-specific factors have been cloned and characterized. HT-B is a pistil-expressed non-S-specific factor identified in Nicotiana, Solanum and Petunia. Here, we report that Petunia HT-B is genetically linked to HTL, an HT-like pistil-specific gene that is not involved in GSI. Further characterization of a BAC clone that contains HT-B showed that HTL is located 〜5kb downstream of HT-B. A 16,876 b genomic sequence that contains the two genes was completely determined. It was found that the transcriptional orientations of the two genes are the same, and they are separated by 4,552 b.