Hyphal Structure

The ability to understand cytoplasmic structure can provide powerful insights into the biology of cells and organisms. This chapter has briefly reviewed the diversity of hyphal structures and presented examples of how bioimaging has contributed to a broader understanding of hyphal biology and phylogenetic relationships between fungal taxa. At the heart of polarized growth is the secretory pathway in which vesicles are targeted to sites of growth and subsequently fuse with the plasma membrane. In mature hyphae of the septate fungi, these events have given rise to the Spitzenkörper, a complex and dynamic structure that clearly influences hyphal growth and morphogenesis. The presence or absence of certain morphological characters (e.g., septa and Woronin bodies) already has been useful in defining higher taxa, especially since evolutionary polarity often can be established using stable phylogenetic trees based on DNA sequences. Ever-enlarging molecular databases, especially those of whole genomes, are allowing us to look for the genetic basis of many structural features, such as the presence or absence of Woronin body matrix proteins. This capability will allow us to understand the basis of these features not only in an evolutionary sense but also in a functional one. Collaboration among different types of fungal biologists including systematists is essential to understanding structure and how it applies to the study of the Fungi.