Characterizing cilium disassembly in the developmental program of chytrid fungi

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Chytrids are one of the only known groups of ciliated fungi and have important ecological roles in soil and aquatic environments. However, very little is known about their cell biology. In order to make chytrids more amenable to study, I have developed various tools to facilitate the use of chytrids as model organisms. Focusing on the non-amoeboid chytrid Rhizoclosmatium globosum and the amoeboid chytrid Spizellomyces punctatus, I have characterized these chytrids' life cycles, optimized imaging techniques, and made preliminary attempts at transformation. I have also identified select genes in their genomes and found that both R. globosum and S. punctatus have most of the expected centrosome and cilium associated genes. However, only S. punctatus has a full set of branched actin nucleation related genes associated with amoeboid motility. After developing these chytrid related tools and resources, I next sought to use these chytrids to study cilium disassembly. Cilia are protrusions from cells containing a tubulin-based structure called an axoneme. They can be involved in motility and sensory functions; however, due to the modified centrioles found at their bases that are used in mitosis, cilia need to be disassembled for progression through the cell cycle. Cilium disassembly is an understudied process, and most of what has been discovered has been found in Chlamydomonas reinhardtii and cultured mammalian cells, which undergo two types of cilium disassembly: gradual shortening and fast severing. However, while chytrids can sever their cilia under stressful conditions, they generally undergo a separate mechanism where their cilia are retracted into their cell body. Thus, a non-model organism is required to study a process that cannot be found in common model systems. I have found that R. globosum and S. punctatus have a common cilium disassembly mechanism of reeling in their axonemes into their cell bodies. However, amoeboid S. punctatus has additional, faster mechanisms of ciliary compartment loss and lash-around retraction, and its initiation of retraction is at least partially actin dependent. Once the axoneme is internalized, its tubulin is degraded over the course of about two hours in both species in a partially proteasome dependent manner. Axoneme disassembly also seems to be partially proteasome dependent, indicating that it is coupled with axonemal tubulin degradation. Overall, I was able to develop tools for chytrid fungi to better characterize cilium retraction and the fate of internalized axonemes.


Type of resource text
Form electronic resource; remote; computer; online resource
Extent 1 online resource.
Place California
Place [Stanford, California]
Publisher [Stanford University]
Copyright date 2021; ©2021
Publication date 2021; 2021
Issuance monographic
Language English


Author Venard, Claire Marie
Degree supervisor Stearns, Tim
Thesis advisor Stearns, Tim
Thesis advisor Cyert, Martha S, 1958-
Thesis advisor Feldman, Jessica L
Thesis advisor Grossman, Arthur (Arthur R.)
Degree committee member Cyert, Martha S, 1958-
Degree committee member Feldman, Jessica L
Degree committee member Grossman, Arthur (Arthur R.)
Associated with Stanford University, Department of Biology


Genre Theses
Genre Text

Bibliographic information

Statement of responsibility Claire Venard.
Note Submitted to the Department of Biology.
Thesis Thesis Ph.D. Stanford University 2021.

Access conditions

© 2021 by Claire Marie Venard

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