Chloroplast Targeting Signal of a Rice Rubisco Activase Gene Enhances Transgene Expression

N-terminal sequence of the protein encoded by rice RCA gene was predicted to be a chloroplast transit peptide.The 144bp fragment of this gene was fused with GFP to construct a transient expression vector pGD-RCATP-GFP for genetic transformation.Transient transformation of tobacco was produced by the Agrobacterium-mediated infiltration method.Fluorescence microscopy analyses demonstrated that,in cells expressing the RCATP:GFP fusion protein,the fluorescence was specifically targeted to chloroplast.Then this fragment was fused with GUS to construct a vector p1300-RCATP-AGS for genetic transformation.To analyze GUS activity for the leaves of the positive plants,we discovered that the RCA TP sequence increased GUS protein expression levels about 3 fold,when compared to without RCA TP sequence.