[Arabidopsis] Similar phenotype in overexpression and knockout

Thomas McKnight via arab-gen%40net.bio.net (by mcknight from mail.bio.tamu.edu)
Tue May 4 14:55:44 EST 2010

Unless you are sure that the knockout lines really don't express the mRNA of interest, it may be that they are actually overexpression lines.  We have found many cases where T-DNA insertions near the ends of genes activate their expression (presumably through the 35S enhancers present in the T-DNA).  If the truncated mRNA can give rise to a functional protein, then the line will behave like an overexpressing line.   

This happens frequently enough that we now order Salk lines with T-DNA insertions near the ends of our favorite genes as a rapid way to examine overexpression.  

For two examples, see:

Ren, S., Boedeker, A., Rathore, K., and McKnight, T.D.  2007. Regulation of telomerase in Arabidopsis by BT2, an apparent target of the TAC1 transcription factor.  Plant Cell 19; 23-31.

Ren, S., Johnston,J.S., Shippen, D. E., and McKnight, T.D. 2004. TELOMERASE ACTIVATOR1 induces telomerase activity and potentiates responses to auxin in Arabidopsis. Plant Cell 16; 2910-2922.

Thomas D. McKnight
Department of Biology
3258 TAMU
College Station, TX  77843

979-845-3896 (voice)
979-845-2891 (fax)

>>> Ido Kron <ido.kron from mail.huji.ac.il> 5/3/2010 7:01 AM >>>
I am puzzled that both over-expression and knockout of the kinase that I am
working on result in the same phenotype (a reduction in the expression of
several putative target genes, compaired with wild-type plants.) Does anyone
know of other cases when over-expression and knockout mutations of a gene
result in similar phenotypes.

Thank you very much,
Ido Kron
The Hebrew University of Jerusalem
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