Abstract: This research aimed to evaluate the specificity of sesquiterpene synthase promoter (SesqPro) activity in the oil palm tissues and tomato hairy roots and to determine the functional region of the promoter. The effect of jasmonic acid (JA) on the promoter activation and gene expression was also analyzed. A series of 5’ sequence deletions on the full-length SesqPro were generated and individually cloned into the pCAMBIA 1301 vector. Functional analysis was carried out on leaves, mesocarp slices and Immature Embryos (IE) of oil palm and tomato hairy roots that had been transformed with full-length SesqPro (PSPr-VF6). GUS expression was found in all the tissues and a higher activity was detected in IE and mesocarp slices. All the constructed derivatives of SesqPro were transformed into IE and mesocarp slices in order to determine the promoter regions which are responsible for gene expression. The reduction of GUS activity was found to be related to the removal of DNA sequences within the promoter region. The promoter was induced by the elicitor molecule JA, thus suggesting the presence of JA responsive elements within the promoter. Incubation with 100 μM of JA showed higher GUS activity in IE and mesocarp slices that had been transformed with PSPr-VF4 to PSPr-VF6. Nevertheless, the GUS activity was drastically reduced in IE and mesocarp slices containing the PSPr-VF3 promoter, suggesting that the presence of the G/A hybrid box located at -622 to -617 act as a specific element in response to elicitors. This study has shown that the action of SesqPro is non-specific and was influenced by JA induction.