Characterization of Fruit-Type Sucrose Synthase Gene Promoters Isolated from Tomato and Japanese Pear

Abstract

We isolated the 5' upstream promoter regions of the fruit-type sucrose synthase (SS) gene from tomato and Japanese pear by inverse PCR. The 5' region of the tomato SS gene (TOMSSF) contained an intron approximately 1.6 kbp long in the 5'untranslated region, whereas the equivalent 5' region in the Japanese pear SS gene (PypSUS1) had no intron. Each region was fused to the β-glucuronidase (GUS) gene and then each construct (TOMSSF 5'::GUS or PypSUS1 5'::GUS) was used to transform tomato. Histochemical analysis of GUS activity of all transformants showed high GUS activity in the fruit. Analysis of the staining pattern in the fruits of all transformants showed staining specific to vascular tissues and testae. The highest level of GUS activity and GUS mRNA was found in fruits at earlier stages of development in all transformants. However, the increase in the level was not observed in the ripening fruits of PypSUS1 5'::GUS lines, indicating that the expression patterns of PypSUS1 5'::GUS tomato were different from those of PypSUS1 in Japanese pear. It may ascribe to the differences in genetic background between tomato and Japanese pear that relate to the mechanisms contributing to the sucrose synthesis during ripening.