Cloning of the promoter region of plasma membrane aquaporin BnPIP1 from Brassica napus and its functional analysis

A 1.6 kb upstream regulatory sequence (GenBank accession no. AF472487) of plasma membrane aquaporin BnPIP1 gene from Brassica napus was obtained by genomic walking based on ligation-mediated PCR method. Sequence analysis indicated that this fragment contained seed germination specific and vascular specific sequences. The 1.6 kb upstream sequence and various 5' end deleted sequences were fused with uidA gene and constructed into plant expression vectors which were used for tobacco transformation. GUS histochemical assay showed that the 1.6 kb fragment had high levels of promoter activity and the GUS staining was mainly distributed in vascular systems and tissues with rapid expanding and proliferating cells. Promoter deletion analysis showed that the deletion of -1610 - -1030 by resulted in a dramatic reduction in GUS activity. It was assumed that there might be cis-acting element(s) existing in this region. Whereas, the region located at -1030 - -902 by strongly inhibited the expression of gus and probably contained negative regulatory element(s). The fragment of -902 - -19 by could also direct gus expression at high level.