Fig. 1

Schematic representation of filamentous fungal growth at cellular and subcellular levels. a Generic development of filamentous growth based on Aspergillus spp. Spores break dormancy and swell during a period of hydration and isotrophic growth, after which polarity is generated and maintained to form a germ tube. Hyphal extension results in branching at apical (tip) and subapical (intercalary) regions. Continued branching forms a network of hyphae termed a mycelium, and conidiophores are generated which bear asexual spores. Note that precise morphology and development will be different between industrially used fungal strains/species, and this is intended as a guide. b Depiction of subcellular organelles, cytoskeleton, and processes that couple growth and protein secretion at the hyphal tip. For explanation, see main text. Proteins are secreted predominantly at the tip; however, septal secretion has also been proposed