Abstract
We previously showed the dual-targeting of Arabidopsis MDAR to Mt and Pl by alternative transcription. To examine the generality of this phenomenon, we analyzed rice MDARs. Five MDAR-like sequences were found in rice genome, and one (hereafter referred to as OsMDAR-A1) had a putative plastid transit peptide at its N-terminus. Its expression had been confirmed by full-length cDNA project. Although no candidate for Mt-type MDAR was found in genome, an ORF (OsMDAR-A2), which has an extra 15-amino-acid-extension at upstream of OsMDAR-A1, was postulated, and its in vivo expression was confirmed by RT-PCR. Comparison between the cDNAs and genome sequence indicates that alternative use of splicing acceptor sites at 5'-UTR leads the two mRNAs from a gene. The N-terminal extensions of OsMDAR-A2 and OsMDAR-A1 fused to GFP were targeted to Mt and Pl, respectively. These results suggest the dual-targeting of rice MDAR to Mt and Pl by different mechanism from Arabidopsis.
