We show that the tightly regulated tetracycline-sensitive Top10 promoter sy
stem (Weinmann et al. Plant J. 1994, 5, 559-569) is functional in Arabidops
is thaliana. A pure breeding A. thaliana line (JL-tTA/8) was generated whic
h expressed a chimeric fusion of the tetracycline repressor and the activat
ion domain of Herpes simplex virus (tTA), from a single transgenic locus. P
lants from this line were crossed with transgenics carrying the ER-targeted
green fluorescent protein coding sequence (mGFP(5)) under control of the T
op10 promoter sequence. Progeny from this cross displayed ER-targeted GFP f
luorescence throughout the plant, indicating that the tTA-Top10 promoter in
teraction was functional in A. thaliana. GFP expression was repressed by 10
0 ng ml(-1) tetracycline, an order of magnitude lower than the concentratio
n used previously to repress expression in Nicotiana tabacum. Moreover, the
level of GFP expression was controlled by varying the concentration of tet
racycline in the medium, allowing a titred regulation of transgenic activit
y that was previously unavailable in A. thaliana. The kinetics of GFP activ
ity were determined following de-repression of the Top10::mGFP(5) transgene
, with a visible ER-targeted GFP signal appearing from 24 to 48 h after de-
repression.