Functional Analysis of SP-DD Synthetic Promoter Using Agroinjection Method in Tobacco Plant

Synthetic pathogen-inducible promoters are suitable alternatives for native promoters in plant genetic manipulation to the purpose of resistant crop production. An ideal pathogen-inducible promoter would only be activated in response to target pathogens. Furthermore، it should express the transgene locally and temporarily. The absence of these characteristics in native promoters have drawn the attentions toward design and construction of synthetic promoters. Some components like cis-regulatory elements are used in construction of synthetic promoters and this provides high flexibility in determining the expression quantity and the inducibility type. One of the most common methods for a synthetic inducible promoter analysis is using Agrobacterium-mediated transient expression system. With this method، Functional analysis of the promoter can be performed in a short time by application of biotic and abiotic treatments and assaying the transgene expression. In this study، the SP-DD synthetic pathogen inducible promoter (containing of two copies of Box D cis-element derived from parsley PR2 promoter) fused with an intron-containing ß-glucuronidase reporter gene was transferred to tobacco leaves (Nicotiana benthamiana) by agroinjection. The promoter function was evaluated in response to salicylic acid treatment and environmental stresses like heat، cold and UV radiation. The results showed that the SP-DD synthetic promoter induced the ß-glucuronidase gene expression in response to salicylic acid and the expression amount increased over time from 2 hours to 24 hours post applicaion. Besides، the promoter showed slight sensitivity in response to heat and cold stresses but the ultraviolet radiation stress had no effect on the promoter induction.