SUMMARY
Ordered collections of Arabidopsis thaliana lines containing mapped T-DNA insertions have
become an important resource for plant scientists performing genetic studies. Previous reports
have indicated that T-DNA insertion lines can have chromosomal translocations associated with
the T-DNA insertion site, but the prevalence of these rearrangements has not been well
documented. To determine the frequency with which translocations are present in a widely-used
collection of T-DNA insertion lines, we analyzed 64 independent lines from the Salk T-DNA
mutant collection. Chromosomal translocations were detected in 12 of the 64 lines surveyed
(19%). Two assays were used to screen the T-DNA lines for translocations: pollen viability and
genome-wide genetic mapping. Although the measurement of pollen viability is an indirect screen
for the presence of a translocation, all 11 of the T-DNA lines showing an abnormal pollen
phenotype were found to contain a translocation when analyzed using genetic mapping. A normal
pollen phenotype does not, however, guarantee the absence of a translocation. We observed one TDNA
line with normal pollen that nevertheless had a translocation based on genetic mapping
results. One additional phenomenon that we observed through our genetic mapping experiments
was that the T-DNA junctions on the 5′- and 3′-sides of a targeted gene can genetically separate
from each other in some cases. Two of the lines in our survey displayed this ‘T-DNA borders
separate’ phenomenon. Experimental procedures for efficiently screening T-DNA lines for the
presence of chromosomal abnormalities are presented and discussed.