Ashbya gossypii grows as multinucleated and constantly elongating hyphae. Nuclei 
are in continuous forward and backward motion, also move during mitosis, and 
frequently bypass each other. Whereas these nuclear movements are well 
documented, comparatively little is known about the density and morphology of 
organelles which very likely influence these movements. To understand the 
three-dimensional subcellular organization of hyphae at high resolution, we 
performed large-scale electron tomography of the tip regions in A. gossypii. 
Here, we present a comprehensive space-filling model in which most 
membrane-limited organelles including nuclei, mitochondria, endosomes, 
multivesicular bodies, vacuoles, autophagosomes, peroxisomes, and vesicles are 
modeled. Nuclei revealed different morphologies and protrusions filled by the 
nucleolus. Mitochondria are very abundant and form a tubular network with a 
polarized spherical fraction. The organelles of the degradative pathways show a 
clustered organization. By analyzing vesicle-like bodies, we identified three 
size classes of electron-dense vesicles (∼200, ∼150, and ∼100 nm) homogeneously 
distributed in the cytoplasm which most likely represent peroxisomes. Finally, 
coated and uncoated vesicles with approximately 40-nm diameters show a polarized 
distribution toward the hyphal tip with the coated vesicles preferentially 
localizing at the hyphal periphery.