Abstract
The present study was conducted to determine efficiency of green tissue-specific (pRCA) and stress-inducible promoters (pRD29A) to express E. coli beta-glucuronidase (gusA) gene in transgenic potatoes compared with constitutive promoter (35S CaMV). The promoter fragments were isolated from their original source and cloned upstream to gusA in pCAMBIA-1301 binary vector to develop plant expression constructs, i.e., pRCA-pCAMBIA and pRD29A-pCAMBIA. Agrobacterium strain GV2260 harboring recombinant plasmids were used to infect leaf discs and internodal explant of Lady Olympia cultivar. GUS histochemical analysis was performed at different stages to determine GUS activity in transgenic plants. To determine activity of stress-inducible promoter (pRD29A), transgenic plants were exposed to heat, drought and combination of both heat and drought stress. The real time (RT-qPCR) and GUS florimetric assays revealed that pRD29A promoter gets more activated under drought, heat and combination of both stresses. GUS expression levels were more than 10 folds high with pRD29A promoter compared to control. Likewise, the reduced transcripts levels of gusA gene under control of pRCA promoter were found in tuber/roots of transgenic plants compared to 35S promoter. GUS florimetric assays also showed decreased or no GUS expression in tubers. In conclusion, the results encourage the appropriate use of promoters to drive the expression of foreign gene(s) for the development of potato lines tolerant to biotic and abiotic stress while minimizing the risks of transgenic technology in potatoes.