A novel fruit-expressed trypsin inhibitor I gene from a wild species of tomato.

A member of the proteinase inhibitor I gene family encoding an inhibitor I protein with a novel trypsin-specific reactive site was isolated from the wild tomato species Lycopersicon peruvianum (L.) Mill. (LA107). The nucleotide sequence of the gene was identical to a previously isolated cDNA clone from L. peruvianum fruit (Wingate, V.P.M., Broadway, R. M., and Ryan, C. A. (1989) J. Biol. Chem. 264, 17734-17738) with the exception of one nucleotide 3 base pairs upstream from the 5' terminus of the cDNA. S1 nuclease protection experiments and RNA blot hybridization analysis show that the gene is developmentally regulated in L. peruvianum fruit and is not the same inhibitor I gene that is wound inducible in leaves. Nucleotide sequences are present in the 5'-flanking sequences of the fruit-specific L. peruvianum gene inhibitor I gene which share similarity with regulatory sequences that have been associated with the regulation of several known elicitor- and ethylene-inducible genes. However, the L. peruvianum motifs are not identical with those of other genes and are probably not functional. Because inhibitor I genes are not expressed or are expressed in very low levels in modern tomato fruit before the onset of ripening but expressed at high levels in fruit of the wild L. peruvianum species, a unique fruit-specific signaling system must therefore be present in L. peruvianum fruit for the transcriptional regulation of the inhibitor I gene which is not present in the fruit of the modern tomato, L. esculentum.