A rice promoter containing both novel positive and negative cis-elements for regulation of green tissue-specific gene expression in transgenic plants

The tissue-specific expression of transgenes is essential in plant breeding programmes to avoid the fitness costs caused by constitutive expression of a target gene. However, knowledge on the molecular mechanisms of tissue-specific gene expression and practicable tissue-specific promoters is limited. In this study, we identified the cis-acting elements of a tissue-specific promoter from rice, P-D540, and tested the application of original and modified P-D540 and its cis-elements in the regulation of gene expression. P-D540 is a green tissue-specific promoter. Five novel tissue-specific cis-elements (LPSE 1, LPSE2, LPSRE 1, LPSRE2, PSE1) were characterized from P-D540. LPSE1 activated gene expression in leaf and young panicle. LPSRE2 suppressed gene expression in leaf, root, young panicle and stem, and PSE1 suppressed gene expression in young panicle and stem. LPSRE1 and LPSE2 had dual roles in the regulation of tissue-specific gene expression,- both functioned as activators in leaf, but LPSRE1 acted as a repressor in stem and LPSE2 as a repressor in young panicle and root. Transgenic rice plants carrying crylAc encoding Bacillus thuringiensis enclotoxin, regulated by P-D540 were resistant to leaf-folders, with no CrylAc protein found in enclosperm or embryo. A reporter gene regulated by a series of truncated P-D540 showed various tissue-specific expression patterns. Different fragments of P-D540 fused with the constitutive cauliflower mosaic virus 35S promoter suppressed 35S-regulated gene expression in various tissues. P-D540 truncated P-D540 and the tissue-specific cis-elements provide useful tools for the regulation of tissue-specific gene expression in rice breeding programmes.