Changes to the cytoskeleton and cell wall underlie invasive hyphal growth. (2004)

View/ Open
Type of Content
Theses / DissertationsThesis Discipline
Cellular and Molecular BiologyDegree Name
Master of SciencePublisher
University of Canterbury. Biological SciencesCollections
Abstract
Tip growth is a form of cellular expansion characteristic of fungal hyphae and some types of plant cells. Currently there is no unified model that satisfactorily describes this in hyphal species. Traditionally turgor has been considered an essential driving force behind cell expansion. In recent years this hypothesis has been challenged by evidence that in some species tip growth can occur despite the absence of measurable hydrostatic pressure. There are currently two contentious theories of hyphal extension. These are the turgor-driven model and the amoeboid-movement theory. Though the essential mechanism underlying cell growth differs between these theories, the actin cytoskeleton is considered important in both. It has been suggested that both the turgor-driven and amoeboid-like modes of growth could occur depending on the whether the hyphae are growing invasively or non-invasively respectively (Money, 1990). It has also been proposed that both modes may occur within the same mycelium (Garrill, 2000). Two distinct patterns of actin have been identified in the hyphal tips of oomycetes. This has lead to the hypothesis that two different mechanisms of apical extension may be employed by some hyphal organisms. During the course of this thesis, actin deplete zones have been observed in a significantly higher number of invasive compared to non-invasive hyphae of the oomycete Achlya bisexualis. Furthermore the difference between burst pressures was found to be lower in invasive hyphae compared to non-invasive hyphae suggestive of a weaker cell wall. A lack of significant difference in turgor pressures between the invasive and non-invasive hyphae of this organism suggests that the deplete zone and weaker wall plays a functional role in enabling hyphae to penetrate substrate. Fractal analysis of mycelial colonies shows that the variation in agar concentration and therefore substrate solidity has a significant effect on mycelial morphology. This is most likely due to an effect at the cellular level. The results of the experiments carried out during the course of this thesis provide the basis for future work towards elucidating the mechanisms of hyphal extension.
Keywords
Actin; hyphae; oomycete; invasive growthRights
Copyright Sophie WalkerRelated items
Showing items related by title, author, creator and subject.
-
F-actin rearrangements and analysis of physical environment of invasive hyphal growth.
Rolston, Laura Elizabeth (University of Canterbury. School of Biological Sciences, 2009)Invasive growth through a substrate requires a massive amount of penetrative force, and this is generated in the space of a few microns in a growing tip. This process is known to be critical in the root hair, pollen tube, ... -
Hyphae-on-a-chip : a microfluidic platform for the study of zoospore germination and protrusive forces in hyphal invasion.
Sun, Yiling (University of Canterbury, 2020)Fungal and oomycete pathogens have a significant influence on species extinctions, food security, ecosystem disturbances, and even human health. The large diversity of pathogenic fungi and oomycetes, and their acquired ... -
The roles of F-actin and integrin-like proteins in hyphal tip growth.
Yu, Yuping (University of Canterbury. Biological Sciences, 2005)This thesis presents an investigation into the role of F-actin and integrin-like proteins in tip growth in the oomycete Achlya bisexualis. Tip growth is a complex process that involves localised extension at the tips of ...