Cover photograph (Copyright © 2007, American Society for Microbiology. All Rights Reserved.): Localization of green fluorescent protein (GFP)-tagged RHO-4 in asexual spores of Neurospora crassa; rho-4 is required for septation. Left column, conidiophores stained with calcofluor; middle column, micrographs showing GFP–NRHO-4 localization; right column, merged images of calcofluor (magenta) and GFP–NRHO-4 (green). In the wild type (top row), GFP–NRHO-4 localization is mostly cytoplasmic after formation of the second septum. In the conidial separation mutant csp-1 (middle row), GFP–NRHO-4 colocalizes with calcofluor staining at primary conidial septa. GFP–NRHO-4 localization in the rdi-1 mutant (bottom row) shows plasma membrane localization. rdi-1 encodes a guanine nucleotide disassociation inhibitor that negatively regulates RHO-4 function by sequestering RHO-4 in the cytoplasm. (See related article on page 1097.)