We are researching various diets and specific nutrients in Drosophila. The question that constantly pops up for the internal discussions is when is the right time to harvest your flies to analyse mRNA (broad variety of targets, inside and outside intestinal system). Will 1 week be too late? Will 6 h be too soon? Is the change in mRNA expression level even that important if you only can see it after few hours but not after few days?

What is your opinion and the experience on the topic?