The 5' flanking sequences of two S alleles in Lycopersicon peruvianum are highly heterologous but contain short blocks of homologous sequences.

To characterize the molecular structure of the S alleles in Lycopersicon peruvianum, we isolated two genomic fragments that corresponded to cDNAs for S11 and S12 RNases from a genomic library of a plant with the S11S12 genotype. The coding regions and the flanking regions in both fragments were sequenced. A single short intron was found in each gene for RNase, and it was located in the previously identified HV2 region [Chung et al. (1994) Plant Mol. Biol. 26: 757]. The site of initiation of transcription of the gene for S11 RNase was determined by a primer extension analysis and a putative TATA box was identified. Three short sequences that were highly homologous in the two S alleles were found within 360 bp upstream of the ATG initiation codon. It is suggested that these sequences might be involved in the regulation of transcription required for the appropriate-level or tissue-specific expression of the S genes in L. peruvianum.