Functional analysis of a reproductive organ predominant expressing promoter in cotton plants

Transgenic Bt insect-resistant cotton plants have high insect resistance in the early stage of development, but relatively low resistance in the late stage. Substituting a reproductive organ-specific promoter for the CaMV35S promoter presently being used could be an ideal solution. For the first time, the promoter sequence of ADP-ribosylation factor 1 (arf1) gene was isolated from Gossypium hirsutumY18 by means of inverse PCR. The sequencing result discovered the unique structure of the arf1 promoter, including four promoter-specific elements, the initiator, TATA box, CAAT box and GC box, and also an intron in 5'-untranslation region. Four plant expression vectors were constructed for functional analysis of the promoter. Based on the pBl121 plant expression vector, four truncated arf1 promoters took the place of the CaMV35S promoter. These vectors were different only in their promoter regions. They were introduced into cotton plants via pollen tube pathway. Histochemical GUS staining and fluorescence quantitative analyses were performed to examine the expression patterns of the GUS gene driven by the 4 arf1 truncated promoters in transgenic cotton plants respectively. The results showed that the arf1 promoter was a typical reproductive organ-specific promoter. Hopefully, the arf1 promoter can be a regulatory element for designing cotton reproductive organs with desired characteristics.