An improved clearing method for GUS assay in Arabidopsis endosperm and seeds

Precise cellular localization of the GUS stain is notoriously difficult in Arabidopsis seeds. Here we report an improved protocol for the clearing of seeds after GUS staining. Incubation in ethanol-acetic acid (EtAc) and Hoyer's medium allows reliable cellular localization of the GUS, even in seeds from late developmental stages. This method also leads to the staining of nucleoli in the endosperm and embryo, facilitating nuclear counts in endosperm development.