Cryptic plasmid pSKU146 from the wall-less plant pathogen Spiroplasma kunkelii encodes an adhesin and components of a type IV translocation-related conjugation system.
A cryptic plasmid of the wall-less plant pathogenic mollicute, Spiroplasma kunkelii CR2-3X, was cloned and its sequence analyzed. The 14,615 bp plasmid, designated pSKU146, has a nucleotide content of 28 mol% G + C, and contains 18 potential protein-coding regions (open reading frames, ORFs), of which six encode proteins that exhibit similarity to virulence-associated proteins involved in cell-to-cell adhesion or conjugal DNA transfer. One ORF encodes a 96 kDa protein, SkARP1, that is highly similar to SARP1 adhesin involved in attachment of Spiroplasma citri to insect vector gut membrane. Five ORFs encode proteins similar to TraE and Mob in walled bacteria, and to ORFs found in the integrative, conjugative element (ICEF) of Mycoplasma fermentans, respectively. Presence of domains similar to proteins of the Type IV secretion system in pathogenic bacteria suggests that spiroplasma possesses a related translocation system. Plasmid pSKU146 also contains two identical oriT regions each containing a nick sequence characteristic of the IncP conjugative plasmid family, as well as a 58 bp palindromic sequence, palSK1. Features in pSKU146 suggest that the plasmid functions as a mobile genetic element in conjugative transmission of spiroplasma pathogenicity-related genes.
Davis
Robert E
RE
Molecular Plant Pathology Laboratory, USDA-Agricultural Research Service, Beltsville, MD 20705, USA. davisr@ba.ars.usda.gov
Dally
Ellen L
EL
Jomantiene
Rasa
R
Zhao
Yan
Y
Roe
Bruce
B
Lin
ShaoPing
S
Shao
Jonathan
J
D018829:Adhesins, Bacterial / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D001665:Binding Sites; D002473:Cell Wall / Q000235:genetics; D003001:Cloning, Molecular; D003227:Conjugation, Genetic / Q000235:genetics*; D008969:Molecular Sequence Data; D010944:Plants / Q000382:microbiology; D010957:Plasmids / Q000235:genetics*; D018741:Replication Origin / Q000235:genetics; D012270:Ribosomes / Q000235:genetics; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013149:Spiroplasma / Q000235:genetics* / Q000472:pathogenicity; D014764:Viral Proteins / Q000235:genetics
D018829:Adhesins, Bacterial; D001426:Bacterial Proteins; C083180:Mob protein, Bacteria; C440889:Spiroplasma citri adhesion related protein P89; D014764:Viral Proteins; C052883:chromosome partition proteins, bacterial