Fluorescent labels for intracellular structures and organelles

31.1 Introduction The sequencing of the genomes of Aspergillus nidulans, Aspergillus fumigatus, and Aspergillus oryzae has ushered in a new era in research with these organisms. In addition, the development of robust and efficient gene targeting, and fusion PCR protocols has reduced to days or weeks tasks that formerly required weeks or months. Nowhere is this more apparent than in the imaging of intracellular structures and organelles. Tagging of proteins with fluorescent moieties [green fluorescent protein (GFP), monomeric red fluorescent protein (mRFP) and others] is now rapid and efficient. Genes encoding proteins of interest can be identified from the genome sequence data and tagged using procedures that do not even require the gene to be cloned in the conventional sense. This allows proteins to be localized accurately in living cells and the movement of these proteins to be followed over time. Organelles can be observed by tagging proteins specific to those organelles with fluorescent moieties. In addition, immunofluorescence microscopy, which has been used for decades, benefits greatly from the ability to epitope-tag proteins rapidly.