Many plant genetic engineering taskss require the spatial expression of genes which in turn depends upon the availability of specific promoters. The present paper analyses the green-tissue characteristics of a new L. gibba rbcS promoter driving the expression of the gus gene in transgenic tobacco. A 1491 bp rbcS (small subunit of ribulose bisphosphate carboxylase) promoter was isolated from Lemna gibba. The sequence analysis revealed that this promoter is different from the previously reported rbcS promoter and is named SSU5C. A 1438 bp fragment of the SSU5C promoter was fused with the gus gene and transgenic tobacco plants were generated. The analysis of T<sub>1</sub> tobacco p1438-gus revealed that GUS expression driven by the SSU5C promoter was detected in the green part of vegetative organs. The promoter deletion analysis confirmed a region from position –152 to –49 relative to the start of transcription containing boxes X, Y and Z, while a positive regulatory region conferred green tissue-specific expression. Further functional analysis of constructs of box-X, Y, Z, which was fused with the basal SSU5C promoter, confirmed that the boxes X, Y and Z represent the new minimized functional promoter, respectively, and are able to direct green tissue-specific expression. This promoter may be used for gene expression in a tissue-specific manner in plant molecular breeding.
Two classes of cis sequences contribute to tissue-specific expression of a PAL2 promoter in transgenic tobacco
