Hi there,

The red color starts to appear when exogenous added adenine becomes limiting for the cell growth. On YEPD without adenine supplementation the carency appears rapidly as growth is fast and exogenous adenine is limited whereas on csm growth is less so exogenous adenine is consumed more slowly. What you could do to get red color more quickly is to limit the supplementation in adenine. BTW: Why don't you just select ade+ clones on csm-ade+galactose?

Hi Dominique,

Thank you for a most informative and helpful answer! We thought about adopting the red/white color assay to identify rare events of NO-interaction (red) on a baseline of positive interaction (white) and therefore the -Ade won't work for us.. on YPD we can't select for the presence of the plasmids. 

Could you elaborate on the addition of Galactose? What function does it serve in your the -Ade selection?  

Hi again,

Actually I wrote galactose but I meant glucose, sorry... So you are more interested in negative interactions than in positives. So ade2 reporter assay is not suitable as such because it's positive selection. What you could do is to first grow selected clones on csm+adenine and then replica plate them onto csm-adenine (both with pressure of selection for plasmids).