Which fleurophore is better to use as a tag in plants, mYFP, EYFP, citrine or mCitrine?

Answer 1

Difficult question especially since you don't define the nature of your experiment.

If you need to be certain that the fluorescent protein doesn't dimerize/oligomerize then you have to go for a monomer.

There are lots of different mutant YFPs.
EYFP was the best of them in terms of quantum yield.
Looking at the EYFP mutations given by CLONTECH (http://www.clontech.com/clontech/techinfo/vectors_dis/pEYFP-Peroxi.shtml), Citrine is effectively EYFP with the additional mutation Q69M.The effect of this mutation is lower pK(a) (5.7) than for previous YFPs, indifference to chloride, twice the photostability of previous YFPs, and much better expression at 37 degrees C and in organelles.

http://www.jbc.org/cgi/content/full/276/31/29188

Thus Citrine seems the best unless you are lookiing at pH or halide sensitivity.

You can easily make the monomeric form of GFP mutants by doing the A206K mutation, so you can construct in 2 steps (first Q69M, then A206K or vice versa) citrine using EYFP as template.
The A206K mutation decreases quantum yield a bit, but not so much.

Science. 2002 May 3;296(5569):855-7.

Partitioning of lipid-modified monomeric GFPs into membrane microdomains of live cells.

Zacharias DA, Violin JD, Newton AC, Tsien RY.