Abstract
PpRPOT1 and PpRPOT2 in Physcomitrella patens have two Met residues in N-terminus. When a construct in which GFP is fused to the 5'-UTR and N-terminal sequence containing two Met (M1 and M48) of PpRPOT1 was introduced into the moss protoplasts, the fluorescence of GFP was localized to mitochondria. GFP was localized to plastid when the translation was forced to start at M1 using a translation leader sequence of rbcS 3A in pea, whereas it was localized to mitochondria when the translation was forced to start at M48. We examined the efficiency of translation from the 5'-upstream sequence of M1 and M48 using GUS fusions. The results indicated that the translation starts exclusively at M48. Therefore, in natural context of PpRPOT1 gene, translation starts at M48 and the product is targeted to mitochondria. This is consistent with the tagetitoxin sensitivity of transcription in isolated plastids and mitochondria.
