Molecular mechanisms of pathogenesis incited by Erwinia carotovora subsp. carotovora

Erwinia carotovora subsp. Carotovora (Ecc) incites soft-rot on many plants. It is believed that soft-rot is due to the concerted activity of extracellular enzymes. Recombinant DNA techniques were used to study the molecular basis of pathogenesis incited by Ecc. Specifically, a clone library of Ecc strain EC14 DNA in plasmid pBR322 was constructed and transformed into Escherichia coli strain HB101. Some of the E. coli strains that contain these hybrid plasmids produce pectinases or cellulase(s). Plasmid pDR1 contains a 3.4 kilobase (kb) EC14 DNA fragment and mediates the production of endo-pectate lyases with isoelectric points (pI) of 9.5 and 7.5 in strain HB101. The pI 9.5 enzyme is believed to be the major extracellular pectolytic enzyme in soft-rot while the pI 7.5 enzyme has no documented counterpart in EC14. Subclone and transposon tn5 analyses of pDR1 indicate that 1.5 kb is necessary for the production of the pI 9.5 and pI 7.5 enzymes and that these enzymes are produced independently of other EC14 pectate lyase enzymes. Plasmid pDR30 contains a 2.1 kb EC14 DNA insert that mediates the production of an endo-polygalacturonase and an exo-pectate lyase in HB101. The exo-pectate lyase encoded by pDR30 produces an inducer of endo-pectate lyase synthesis as a reaction product. The endo-polygalacturonase encoded by pDR30 is thought to play a role in plant cell wall pectic polymer degradation. Restriction endonuclease and Southern hybrididizatian analyses indicate that the EC14 genes on plasmids pDR1 and pDR30 are not part of the same operon. Escherichia coli strain HB101 containing plasmid pDR1 or plasmid pDR30 is unable to macerate potato tuber slices. However, HB101 containing plasmids pDR1 and pDR30 can cause limited maceration of potato tuber slices. There appears to be a genetic interaction between plasmids pDR1 and pDR30 in maceration of potato tuber tissue. However, the EC14 gene(s) contained on plasmid pDR1 are transcribed independently of the EC14 genes contained on plasmid pDR30. It is possible that transcription of certain pectolytic enzymes independent of other pectolytic enzymes provides a flexible system for plant cell wall pectic polymer degradation.

Name thesis:degree_name

Ph. D.

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Plant Pathology

Department dc:contributor.department

Plant Pathology

Grantor dc:publisher

Virginia Polytechnic Institute and State University

Year dc:date.issued

1985

Author dc:creator

• Roberts, Daniel Paul

Chair dc:contributor.committeechair

• Lacy, George H.

Committee members dc:contributor.committeemember

• Moore, L.D.
• Tolin, Sue A.
• Johnson, J.L.
• Bates, Robert C.

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en_US

Handle dc:identifier.uri

http://hdl.handle.net/10919/71251

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/71251