Functional Studies of Complementary Sense Promoter (Replicase Promoter) from Tomato Yellow Leaf Curl Virus: Evidence for Transcription Capability in Non‐host Plants

Abstract

The complementary sense promoter C1 that regulates the transcription of replicase gene in geminiviruses was cloned from tomato yellow leaf curl virus. A transcription fusion of β‐glucuronidase gene (GUS) coding sequence to complementary sense promoter, that replaced the viral replicase coding sequence, was constructed. Protoplasts of Nicotiana tabacum were electroporated to introduce the GUS gene controlled by the C1 promoter. The level of GUS transient gene expression was enhanced by the increase of the plasmid DNA concentration. Fluorometric GUS assays showed that the C1 promoter has a lower expression compared to the e35S promoter. Bombardment of the constructed plasmid. containing Cl promoter‐GUS ORF‐NOS terminator (pKSIR‐E), was performed to different plant genetic backgrounds and followed by the histochemical GUS assays. The results showed that there were GUS activities expressed in tomato (Lycopersicon esculentum), tobacco (Nicotiana tabacum) and datura (Datura stramonium), as host plants. While in non‐host plants, the GUS activities were observed in faba bean (Vicia faba) and squash (Cucurbita pepo), as examples of dicot plants, but not in maize (Zea mays) as a representative of monocote.