Functional assessment of plastid signal peptide sequences LIM14 and AtCPrecA in localization of Green Fluorescent Protein (GFP) and beta-glucuronidase (GUS) reporter proteins in transgenic potato plants

In this study، signal peptide sequences of Lillum longiflorum anther-specific protein LIM14 and ATCPrecA، a protein with the origin of A. thaliana that had the characteristics of chloroplast signal sequence were independently fused to the N terminus of the green fluorescent protein (GFP) and β-glucoronidase (GUS) genes and subsequently transferred to potato (Solanum tuberosum cv. Kardal) as an important starch storage plant by Agrobacterium-mediated transformation. Fluorescence microscopy and GUS staining showed that the recombinant LIM14-GFP fusion protein was targeted to the amyloplast and chloroplast of transgenic potato plants. Quantitative assay of GUS showed that the level of expression in the enriched amyloplast fragment of signal peptide included plants is higher than the GUS control transformed plants. ATCPrecA is a protein with the origin of Arabidopsis thaliana that had the characteristics of chloroplast signal sequence in N-terminus. To study the function of the transit peptide of ATCPrecA، full length cDNA was fused to the N-terminus of the GFP to make recombinant protein. ATCPrecA-GFP was transferred to potato by Agrobacterium-mediated transformation and transiently expressed in onion (Allium cepa L.) epidermal cells via microprojectile bombardment. According to the results of this research، we concluded that the transit sequence of both LIM14 and ATCPrecA were functional and were capable of directing recombinant proteins into plastids.