LAUSR

Identifying novel promoters with specific temporal and spatial expression patterns is crucial for crop biotechnology. In this study, we isolated a fruit-specific promoter in tomato, HISTIDINE DECARBOXYLASE A (SlHDC-A) promoter. Through RNA-seq and RT-PCR analysis, we found that SlHDC-A was predominantly expressed in fruits and that its expression was stable in fruits during ripening. These results suggest that the promoter of SlHDC-A might have the ability to determine fruit-specific gene expression. To test this possibility, we generated transgenic tomato transformed with SlHDC-A::GUS and 35S::GUS. Unlike 35S::GUS transgenic tomato with constitutive expression in various tissues, SlHDC-A::GUS transgenic plants showed fruit-specific expression of GUS. The intensity of GUS activity in fruits of SlHDC-A::GUS transgenic plants was approximately tenfold higher than that in fruits of 35S::GUS transgenic plants. The core region responsible for its fruit-specific expression was identified by promoter deletion analyses. Removal of the − 880 to − 577 region abolished the fruit-specific expression of SlHDC-A promoter. This suggests that the − 880 to − 577 region is the core region responsible for the fruit-specific expression of SlHDC-A. This finding was further supported by analysis of chimeric fusion promoter. Unlike 35S minimal promoter which had no activity to express GUS, the chimeric fusion promoter of the core region and 35S minimal promoter showed fruit-specific expression similar to intact SlHDC-A promoter. Collectively, these findings indicate that the promoter of SlHDC-A is fruit-specific and the − 880 to − 577 region is the core region of SlHDC-A promoter.