Process of reductive evolution during 10 years in plasmids of a non-insect-transmissible phytoplasma.
A non-insect-transmissible phytoplasma strain (OY-NIM) was obtained from insect-transmissible strain OY-M by plant grafting using no insect vectors. In this study, we analyzed for the gene structure of plasmids during its maintenance in plant tissue culture for 10 years. OY-M strain has one plasmid encoding orf3 gene which is thought to be involved in insect transmissibility. The gradual loss of OY-NIM plasmid sequence was observed in subsequent steps: first, the promoter region of orf3 was lost, followed by the loss of then a large region including orf3, and finally the entire plasmid was disappeared. In contrast, no mutation was found in a pseudogene on OY-NIM chromosome in the same period, indicating that OY-NIM plasmid evolved more rapidly than the chromosome-encoded gene tested. Results revealed an actual evolutionary process of OY plasmid, and provide a model for the stepwise process in reductive evolution of plasmids by environmental adaptation. Furthermore, this study indicates the great plasticity of plasmids throughout the evolution of phytoplasma.
Ishii
Yoshiko
Y
Department of Agricultural and Environmental Biology, The University of Tokyo, Yayoi, Bunkyo-ku, Japan.
Oshima
Kenro
K
Kakizawa
Shigeyuki
S
Hoshi
Ayaka
A
Maejima
Kensaku
K
Kagiwada
Satoshi
S
Yamaji
Yasuyuki
Y
Namba
Shigetou
S
D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D043171:Chromosomal Instability; D017931:DNA Primers / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D019143:Evolution, Molecular; D005798:Genes, Bacterial; D007303:Insect Vectors / Q000382:microbiology; D008969:Molecular Sequence Data; D045582:Phytoplasma / Q000235:genetics* / Q000472:pathogenicity; D010935:Plant Diseases / Q000382:microbiology; D010944:Plants / Q000382:microbiology; D010957:Plasmids / Q000235:genetics*; D016133:Polymerase Chain Reaction; D011995:Recombination, Genetic; D017386:Sequence Homology, Amino Acid
D001426:Bacterial Proteins; D017931:DNA Primers; D004269:DNA, Bacterial