Complementation analysis of Agrobacterium tumefaciens Ti plasmid mutations affecting oncogenicity

Area of Science:

• Molecular Biology
• Microbial Genetics

Background:

• Agrobacterium tumefaciens is a plant pathogen that utilizes the Ti plasmid for tumor formation.
• Understanding the genetic basis of Ti plasmid function is crucial for controlling plant diseases.

Purpose of the Study:

• To construct a versatile cosmid vector for cloning large DNA fragments from the Ti plasmid.
• To utilize this vector for functional complementation of Ti plasmid mutations.

Main Methods:

• Construction of a wide host range cosmid vector by inserting a lambda cos site into pRK2501.
• Generation of a cosmid library of the Agrobacterium tumefaciens pTiA6 plasmid.
• Complementation analysis of Tn5-induced Ti plasmid mutations using the cosmid library.

Main Results:

• The constructed cosmid is maintained in Agrobacterium tumefaciens and is compatible with the Ti plasmid.
• Five avirulent mutations outside the T-DNA region were complemented in trans.
• Mutations within the T-DNA and two outside the T-DNA could not be complemented in trans in a REC- host.

Conclusions:

• The developed cosmid vector is effective for cloning and functional analysis of Ti plasmid genes.
• This approach facilitates the identification and characterization of genes involved in Agrobacterium tumefaciens virulence.
• The study highlights the utility of cosmid complementation for dissecting complex genetic elements like the Ti plasmid.