The rice OsLTP6 gene promoter directs anther-specific expression by a combination of positive and negative regulatory elements

Characterization of tissue-specific plant gene promoters will benefit genetic improvement in crops. Here, we isolated a novel rice anther-specific plant lipid transfer protein (OsLTP6) gene through high through-put expressional profiling. The promoter of OsLTP6 was introduced to the upstream of the uidA gene, which encodes β-glucuronidase (GUS), and transformed into rice plants for functional analysis. Histochemical and fluorometric GUS assay showed that GUS was specifically expressed in the anthers and pollens in OsLTP6 promoter::uidA transgenic plants. Transverse section of the rice anther further indicated that the OsLTP6 promoter directed the reporter gene specifically expressed in anther tapetum. To identify regulatory elements within OsLTP6 promoter region, four progressive deletions of the OsLTP6 promoter were constructed. The results indicated that the OsLTP6 promoter achieved anther-specific expression through a combination of positive and negative regulatory elements. A 26-bp motif upstream of TATA box was a key transcriptional activator for OsLTP6 gene. CAAT box and GTGA box were the putative motifs to increase the transcription level to full expression. Two negative regulatory elements were also found in two distinct regions within this promoter. They repressed the expression in leaf and stem, respectively. These results revealed the regulating complexity of anther-specific expression.