Functional analysis of the Arabidopsis thaliana poly(A) binding protein PAB5 gene promoter in Nicotiana tabacum.

Poly(A) binding (PAB) proteins play an important role in posttranscriptional regulation by stabilizing mRNA and initiating translation in eukaryotes. Previous studies have shown that the expression of PAB5 gene encoding one of the poly(A) binding proteins (PABPs) in Arabidopsis thaliana is restricted to pollen, ovule and early embryogenesis. To investigate the tissue-specific expression of the PAB5 promoter, a series of promoter deletions (from -1,804, -1,653, -1,334, -1,014, -715, -424 and -175 to +185) were fused to the uidA reporter gene (GUS) and transformed into tobacco plants (Nicotiana tabacum L.). The results showed that GUS expression driven by the full-length PAB5 promoter was detected in floral organs (pollen, ovule, anther, stigma) and immature seeds, but not in vegetative tissues (root, stem, leaf) and mature seeds. Deletion analysis of the PAB5 promoter region revealed that promoters longer than -1,334 had the similar GUS expression level in pollen, ovule and immature seeds, whereas further 5' deletions resulted in a considerable reduction in GUS activity. These results indicated that the region between -1,653 and -1,014 was necessary to direct the tissue-specific expression of PAB5 promoter during development.