Please help to work it out,

There are lots of examples. It sometimes happens when overexpressing enzymes placed early in metabolic pathways, which generally has little effect on the overall rate of the pathway, compared to those enzymes placed close to the end product, which are usually rate-limiting. Also, if a protein requires an accesory protein (which functions as cofactor, activator or modifier), overexpression of the first protein might not result in an increase in the active form of that protein, since the accesory protein will still be limiting. These papers can give you a couple of examples in plants:

http://www.ufv.br/dbv/pgfvg/BVE684/htms/pdfs_revisao/metabolismo/flux.pdf

http://www.plantcell.org/content/21/9/2797.full

Thank you very much!

Hey Gustavo, thank you for your nice answer! In my question, I suppose the gene overexpressed in wild type plant can be translated into protein which has function in the transgenic plant. There must has some genes can rescue the mutant plant, but no expected phenotype when overexpress in the wild type.

In those examples I mention, you can observe a phenotype when the genes are mutated or silenced, and the wild-type phenotype can be recovered when expressing the gene in the mutant background, which means the protein is functional. But in these particular cases the activity of the protein does not depend solely on its expression level or concentration in the cell. For example, if it requieres a companion protein for being active, this second protein within the cell will be a limiting factor for the activity of the overexpressed protein. If this second protein maintains wild-type levels, then the activity of the overexpressed protein will be wild-type, regardless of the expression level. Hope it makes sense, and that I am really answering your question.

Hi

It depends on function of proteins, if involved in some enzymatic pathways, as Gustavo said, OE may or may not give any phenotypes.

If proteins are involved in DNA surveillance (recombination, MMR etc), OE usually have minimal consequence although KO will have major phenotypic consequences.

It also depends abundance and specificity of particular protein in mother nature. Usually proteins which are already abundant in wild type, OE will not hurt them. But very abundant and tissue specific proteins can not tolerate OE.

It is possible that your plants have very specific OE effects. Look carefully flowers parts. If you know the function and location of your protein, you can also try some molecular phenotypes.

Very good talking both of you! The OE level is the key.. I agree with "Usually proteins which are already abundant in wild type, OE will not hurt them. But very abundant and tissue specific proteins can not tolerate OE." Keep discussing with example pls!

Do you have examples for this conclusion? thanks a lot!

plz check with localization as I had similar experience when I was working with mammalian cells.Sometimes one find a difference in solubility too.