Construction of Flower-specific Chimeric Promoters and Analysis of Their Activities in Transgenic Torenia

Flower-specific promoters can enable transgenic enhancement of valuable ornamental traits, including flower shape and color. However, the identification of strong, tissue-specific promoters remains a limiting factor. To obtain enhanced flower-specific promoters, we constructed four chimeric promoters (p35S-PCHS-abroken vertical bar, p35S-LCHS-abroken vertical bar, pOCS-PCHS-abroken vertical bar and pOCS-LCHS-abroken vertical bar) combining the 35S or OCS enhancer fused to a 302 bp CHSA core promoter fragment from petunia (PCHS) or a 307 bp CHS core promoter fragment from lily (LCHS), and also containing an omega element (abroken vertical bar). Each promoter was fused to the beta-glucuronidase (GUS) reporter gene, and we examined the levels and tissue specificity of GUS expression in transgenic Torenia fournieri. p35S-PCHS-abroken vertical bar and p35S-LCHS-abroken vertical bar drove strong, constitutive GUS expression in all tissues, especially in colored corollas (p35S-PCHS-abroken vertical bar) or in colored corollas and roots (p35S-LCHS-abroken vertical bar). pOCS-PCHS-abroken vertical bar drove stronger GUS expression in colored corollas than in other tissues but expression was weaker than that of p35S-PCHS-abroken vertical bar. pOCS-LCHS-abroken vertical bar drove GUS in colored corollas but also in roots. Among the four chimeric promoters, pOCS-PCHS-abroken vertical bar exhibited stronger activity only in colored corollas, making it useful for transgenic enhancement of floral traits, such as expressing 'blue genes' in lily to produce new lines with blue flowers.