Potato and Tomato Forever Young Genes Contain class-I Patatin promoter-like Sequences

Abstract

Class-I patatin genes from potato, encoding the major storage protein in tubers, contain promoter repeat sequences, which are critical for developmental and metabolic regulation. Previously, RFLP mapping indicated the patatin genes of potato and tomato reside in orthologous loci near the end of the long arm of chromosome VIII. Interestingly, a DNA sequence homologous to the promoter of the potato class-I patatin gene was mapped to the middle of chromosome III in the tomato and potato genomes [Ganal et al., Mol. Gen. Genet. 225, 501-509 (1991)]. We isolated and characterized genomic clones containing the class-I Patatin Promoter-Like sequences (PPL) from tomato, S. bulbocastanum, and S. tuberosum. Sequence analyses reveal that these PPL sequences are highly conserved, as compared to the repeat sequence of the patatin promoter, particularly with respect to the critical regulatory ciselements. These PPL sequences are located upstream of the translational initiation site of Forever Young genes, which encode proteins belonging to a large family of oxidoreductases with conserved structural motifs. The Forever Young genes from tomato and S. bulbocastanuin both contain eight exons and seven introns. Six of the introns are uniquely large, in the range of 418—2,092 bp. Sequence conservation suggests that the class-I patatin repeat and the PPL from Forever Young genes may have a direct phylogenetic relationship and may regulate expression of their respective genes through common cis- and trans-factors.