Similar phenotype in overexpression and knockout

[Ido Kron]

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

[Charles S. Gasser]

Ido,
We saw similar ovule phenotypes from loss of function of Class III
HD-Zip genes, and from the gain of function (over/ectopic expression)
effects of micro-RNA resistant alleles of these same genes. We
included discussion of this in a publication:

Kelley, DR, Skinner, DJ, Gasser, CS (2008) Roles of polarity
determinants in ovule development. Plant J., 57:1054-1064.

http://www3.interscience.wiley.com/journal/121540116/abstract
--
=======================================
Charles S. Gasser
Professor
Dept. of Molecular and Cellular Biology
University of California, Davis
1 Shields Ave.
Davis, CA 95616

104 Briggs Hall
csga...@ucdavis.edu
http://www.mcb.ucdavis.edu/faculty-labs/gasser/gasser-lab.html
Tel. 530 752-1013
FAX 530 752-3085

[Veerappan, Vijay]

This beautiful paper should answer your questions.

Ulker B, Peiter E, Dixon DP, Moffat C, Capper R, Bouche N, Edwards R, Sanders D, Knight H, Knight MR: Getting the most out of publicly available T-DNA insertion lines.

Plant J 2008, 56(4):665-677.

Good luck,

Vijay Veerappan
Post-Doctoral Fellow, Randy Allen’s Lab
________________________________
Plant Biology Division
The Samuel Roberts Noble Foundation
2510 Sam Noble Parkway
Ardmore, OK 73401
Telephone 580.224.6704 (Off.) | Fax 580.224.6692

[Thomas McKnight]

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....@mail.huji.ac.il> 5/3/2010 7:01 AM >>>

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在 2010年5月3日星期一 UTC-3上午9:01:31，Ido Kron写道：

Hello Dr. Kron,

I am faced with the same situation as you posted here. May you tell me how you interpret your data finally?

Thanks in millions,
Arthur

[Charles S Gasser]

We found similar phenotypic effects on ovule development from over/ectopic expression and loss of function for Class III HDzip genes.  We believe that these genes act in opposition to other genes and disruption of a balance in either direction leads to similar phenotypic effects.  We published this explanation:

Kelley, D. R., Skinner, D. J., and Gasser, C. S.  (2009) Roles of polarity determinants in ovule development. Plant J. 57: 1054-1064.
doi: 10.1111/j.1365-313X.2008.03752.x
 Hope this is useful.  At least you could reference that such a thing has been previously observed.

Chuck Gasser

==============
Charles S. Gasser
Professor Emeritus

Dept. of Molecular and Cellular Biology
University of California, Davis
1 Shields Ave.
Davis, CA  95616

104 Briggs Hall

530 752-1013

[Charles S Gasser]

Posted by Brian Ellis, UBC:

You might find this article interesting, as another example of this phenomenon.
 
Samuel and Ellis, Plant Cell 14:2059-2069 (2002)   
http://www.plantcell.org/cgi/doi/10.1105/tpc.002337
 
Brian Ellis