ABSTRACT
CONTENTS 14.1 Introduction .............................................................................................................................. 211 14.2 Patterns of Cellular Morphogenesis in Aspergillus nidulans .................................................. 212 14.3 Morphogenetic Paradigm ......................................................................................................... 213 14.4 Hyphal Tip ................................................................................................................................ 214
14.4.1 Landmarks ................................................................................................................... 214 14.4.2 Signals ......................................................................................................................... 214 14.4.3 Morphogenetic Machinery .......................................................................................... 215
14.5 Septum Formation .................................................................................................................... 216 14.5.1 Landmarks ................................................................................................................... 216 14.5.2 Signals ......................................................................................................................... 217 14.5.3 Morphogenetic Machinery .......................................................................................... 218
14.6 Patterns of Morphogenesis During Development .................................................................... 218 14.7 The Future ................................................................................................................................ 219 References ........................................................................................................................................... 219
14.1 Introduction Filamentous fungi are defi ned by their ability to form highly polarized hyphae that enable the effi cient colonization of diverse environments. Several recent reviews have summarized the cellular functions and mechanisms involved in the morphogenesis of hyphal cells [1-5]. These reviews rightfully emphasize that much of our molecular understanding of hyphal morphogenesis derives from the deep insights that have been acquired into the analogous processes that drive the establishment and maintenance of cellular polarity in the yeast Saccharomyces cerevisiae. However, it has become increasingly apparent that hyphal morphogenesis involves a more elaborate set of core processes that are regulated in ways that differ from yeast. The completion of multiple fungal genome sequences and the development of tools that make it possible to undertake high-throughput functional genomic studies in fi lamentous fungi (see Ref. 6) will greatly facilitate the analysis of these processes and their regulation. The fi lamentous fungus Aspergillus nidulans possesses many attributes that make it an ideal system for the characterization of the functions required for hyphal morphogenesis. These include the coordination of morphogenesis with spore germination and the duplication cycle, the availability of numerous morphogenetic mutants, and the ability to rapidly investigate gene function. The goals of this review are to describe the patterns of cellular morphogenesis in A. nidulans, briefl y summarize the gene functions known to be involved in morphogenesis, and defi ne some of the important issues to be addressed in the future.
