3 Hyphal Tip Growth in Filamentous Fungi
Hyphae of filamentous fungi extend at the apex by a polarized mechanism that involves the highly ordered and regulated delivery of secretory vesicles. In Dikarya fungi these tip-directed vesicles accumulate temporarily at the Spitzenkörper (Spk) before be
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Hyphal Tip Growth in Filamentous Fungi
M. RIQUELME1, R.W. ROBERSON2, E. SA´NCHEZ-LEO´N1
CONTENTS I. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II. Hyphae and Other Forms of Tip Growth . . . . III. Cell Wall: Growth and Remodeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IV. The Hyphal Tip . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. Spitzenko¨rper or Apical Vesicle Crescent . . . . 1. Organization, Ultrastructure, Composition . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. Diversity Across Fungal Taxa . . . . . . . . . . 3. Spk Behavior and Direction of Growth: Tip Orienteering . . . . . . . . . . . . . . . . . . . . . . . 4. Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5. Ontogeny . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B. Cytoskeleton . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1. Microtubules . . . . . . . . . . . . . . . . . . . . . . . . . . . 2. Actin Microfilaments . . . . . . . . . . . . . . . . . . . 3. Septins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. Molecular Motors . . . . . . . . . . . . . . . . . . . . . . V. The Secretory Machinery . . . . . . . . . . . . . . . . . . . VI. The Role of “Omics” Studies Toward Understanding Tip Growth . . . . . . . . . . . . . . . . . VII. Conclusions and Perspectives . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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I. Introduction All cells, including fungal hyphae, grow through a balanced and regulated set of complex biochemical and biophysical interactions. The components of the hyphal cytoplasm are
1
Department of Microbiology, Center for Scientific Research and Higher Education of Ensenada (CICESE), Ctra. EnsenadaTijuana No. 3918, Ensenada, Baja California 22860, Mexico; e-mail: [email protected] 2 School of Life Sciences, Arizona State University, Tempe, AZ, USA
similar to those of other heterotrophic eukaryotic organisms; however, because of the polarized mode of growth and diverse ecological interactions of filamentous fungi, hyphae also contain organelles and inclusions that are unique to the Mycota. Though superficially discrete and independent, the cytoplasmic components are in fact interconnected directly or indirectly to maintain the highly ordered and polarized organization of the hypha. Fungal cellular and molecular biologists often concentrate their attention toward narrow questions due to the complexity of the total systems being investigated. The growing number of fungal genomes sequenced, the availability of mutants, and the progress made in live imaging techniques and biochemical analysis have greatly contributed to gain a vast amount of knowledge regarding components and mechanisms involved in hyphal polarity and morphogenesis, cytoskeleton function, vesicle trafficking, and nuclear division. Yet there is not a unified understanding on how these ele
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