In planta expression of a protein encoded by the extrachromosomal DNA of aphytoplasma and related to geminivirus replication proteins

A new extrachromosomal DNA, EcOYW1, was cloned from the onion yellows phyto plasma (OY-W). Southern blot and PCR analysis showed that EcOYW1 is not pre sent in the OY-M. a mild symptom line derived from OY-W, We determined the complete nucleotide sequence of EcOYW1; it is a circular dsDNA of 7.0 kbp i n length, which contains seven ORFs. ORF1 encoded a homologue of the gemini virus Rep protein. Western immunoblot analysis revealed that this Rep homol ogue is expressed in OY-W infected plants, Suggesting that EcOYW1 replicate s via a geminivirus-like rolling-circle replication mechanism. EcOYW1 is th e first phytoplasmal extrachromosomal DNA shown to express encoded genes.