T-DNA border sequences required for crown gall tumorigenesis.

Area of Science:

• Molecular Biology
• Plant Pathology

Background:

• Agrobacterium tumefaciens-mediated transformation relies on the transfer and integration of T-DNA.
• The tumor-inducing plasmid (pTiA6NC) contains left (TL) and right (TR) T-DNAs, each bordered by direct repeats.

Purpose of the Study:

• To investigate the role of sequences flanking the 23-bp border repeat in T-DNA transmission.
• To determine if additional sequences beyond the border repeat are required for efficient virulence.

Main Methods:

• Construction of a deletion mutant lacking three potential right border repeats.
• Reintroduction of restriction fragments containing the TL right border repeat at a new location.
• Assessing virulence restoration by fragments with varying flanking sequences and orientations.

Main Results:

• Deletion of right border repeats significantly attenuated virulence.
• Fragments with at least 67 bp left and 1035 bp right flanking sequences fully restored virulence.
• Smaller flanking sequences partially restored virulence, indicating their stimulatory role in T-DNA integration.
• The orientation of the right border repeat influenced its efficiency in promoting T-DNA transfer and integration.

Conclusions:

• T-DNA transmission efficiency is significantly influenced by flanking sequences adjacent to the border repeat.
• Specific flanking regions and their orientation are critical for optimal T-DNA integration and plant tumor formation.