A plasmid from a non-insect-transmissible line of a phytoplasma lacks two open reading frames that exist in the plasmid from the wild-type line.
Two novel rolling circle replication (RCR) plasmids, pOYM (3932 nt) and pOYNIM (3062 nt), were isolated from a mildly pathogenic variant line (OY-M) and a mildly pathogenic plus non-insect-transmissible line (OY-NIM), respectively, of onion yellows (OY) phytoplasma, a plant and insect endocellular mollicute. OY-M was isolated from an original wild-type line (OY-W) after regular maintenance using alternate plant/insect infections, while OY-NIM was further isolated from OY-M after maintenance by plant grafting without insect vectors. The RCR-initiator proteins (Rep) of both plasmids, which have a characteristic structure with both plasmid- and virus-like domains, were highly homologous to that of a previously described OY-W plasmid, pOYW (3933 nt), and were expressed in OY-M- and OY-NIM-infected plants, indicating that this replicon is stably maintained in the phytoplasma. Interestingly, pOYNIM lacked two ORFs that exist in both pOYW and pOYM, which encode a single-stranded DNA binding protein (SSB) and an uncharacterized putative membrane protein, indicating that these two proteins are not necessary for the phytoplasma to live in plant cells. These are the first candidates as phytoplasma proteins possibly related to host specificity.
Nishigawa
Hisashi
H
Department of Agricultural and Environmental Biology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 202 Bioscience Building, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8562, Japan.
Oshima
Kenro
K
Kakizawa
Shigeyuki
S
Jung
Hee-Young
HY
Kuboyama
Tsutomu
T
Miyata
Shin-ichi
S
Ugaki
Masashi
M
Namba
Shigetou
S
D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D015152:Blotting, Northern; D015139:Blotting, Southern; D031202:Chrysanthemum / Q000378:metabolism / Q000382:microbiology; D003001:Cloning, Molecular; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004268:DNA-Binding Proteins; D005838:Genotype; D007150:Immunohistochemistry; D007313:Insecta / Q000382:microbiology; D008969:Molecular Sequence Data; D009154:Mutation; D016366:Open Reading Frames / Q000235:genetics*; D010957:Plasmids / Q000235:genetics*; D017422:Sequence Analysis, DNA; D008973:Tenericutes / Q000235:genetics* / Q000472:pathogenicity; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014774:Virulence / Q000235:genetics
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D015534:Trans-Activators; C045264:replication initiator protein; D004265:DNA Helicases