Like the title explains I am looking for a way to exclusively label microtubule minus end in vivo. Looking through the literature I could not find any techniques yet. Do you have an idea?
γ-Tubulin is specifically localized to the minus end of microtubules. GFP labeled γ-Tubulin can be used to label the minus ends in-vivo and without the requirement of staining. Fan et al have developed a phage display antibody specific to α-Tubulin that can be used to visualize minus ends. See the figure below.
The image is an electron-micrograph but it is certainly possible to do a fluorescent microscopy after IHC staining.