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GUS expression

Leonard N. Bloksberg bloksber at pilot.msu.edu
Tue Jun 7 12:10:00 EST 1994

> Re: Thoma et al. Plant Physiology 105:35-45 (1994) and Uknes et al. Plant
> Cell 5: 159-169.
>         In the first paper the authors describe  a lipid transfer protein
> promoter/GUS fusions in transgenic Arabidopsis. GUS activity appears in the
> pollen but the LTP mRNA does not. In the second paper a similar result was
> found with the PR-1a promoter in tobacco. There the authors also tested a
> second reporter gene and found no activity in tobacco, suggesting that the
> ectopic expression was caused by the GUS coding sequences.
> I wonder how prevelant ectopic GUS expression in pollen really is? I assume
> the following to be true:
>         *there is no GUS activity in pollen of untransformed plants
>         *there is no GUS activity in pollen of plants transformed with
> pBI101  (poly-linker fused to GUS with nos 3')
>         *most constructs introduced into plants do not promote GUS
> expression in pollen
>   I would appreciate hearing from anyone who has detected GUS expression in
> pollen and whether they looked for the endogenous gene in pollen by in situ
> hybridization. Also, has anyone looked into whether the GUS gene effect is
> transcriptional or post-transcriptional? I guess I'm confused because
> ectopic expression in pollen is not found in all transgenics (I assume),
> and most of the reports of pollen specific expression are backed up by in
> situ or northern data. Love to hear from any interested parties!
> Mary Williams (Sussex lab)
The paper discussing native GUS activity in 49 different plant species is
Hu, et al, 1990, "Intrinsic GUS-like activities in seed plants."  Plant Cell
Reports, 9:1-5.  They did not look at Arabidopsis.  They did find GUS-like 
activity in every plant which was tested extensively.  The only plants where
no GUS-like activity was found were not tested as extensively as the others.
It has also been brought to my attention (unreferenced) that this GUS-like
activity may be due to the microflora/fauna of the plant rather than the 
plant itself.  With these 2 bits of information, I would venture to say that
testing GUS activity in non-transformed control plants grown side by side 
with the experimentals is absolutely essential.  I don't think it is 
appropriate for an editor to accept a paper without this simple but crucial 
control.  Let's face it; experiments without controls are not science, and 
cannot be used to build further hypotheses upon.  If any of us wants to 
follow up on this work, we will have to do the controls ourselves.  This 
means re-doing the experiment ourselves as if it was never done in the first
place.  The first paper, without controls, adds nothing to the body of science.
Leonard N. Bloksberg
bloksber at pilot.msu.edu

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