Isolation and functional characterization of a PISTILLATA-1 gene promoter from Brassica napus

The PISTILLATA is a floral organ identity gene required for the flower development. To gain a better understanding of the BnPI -1 promoter function, the promoter 5′ deletion analysis was conducted, both in transgenic Brassica napus and transgenic Arabidopsis . In the β-glucuronidase (GUS) expression assay of transgenic B. napus , most of the 5′ deletion constructs of the BnPI -1 promoter expressed the GUS gene strongly in all organs of the flower except the style, and deletion up to −326 bp region (removed up to the G-box located near the TATA-box) reduced dramatically the GUS expression, and deletion up to −150 bp region (removed up to the TATA-box) abolished the GUS expression. In the GUS fluorometric assay, GUS activity in the flower was about 4-fold higher than that in seed or silique, and GUS activity in the leaf was not detected. The GUS expression patterns in transgenic Arabidopsis were similar to those in transgenic B. napus . These results suggest that the BnPI -1 promoter can lead the foreign gene expression mainly in the floral-tissue, which is shown to be regulated by the G-box element responsive to basic leucine-zipper transcription factors.