Poster: Integrated Plant Biology
Abs #
79: Decreased resistance to environmental stress correlates with a wall defect in a Chlamydomonas monoica zygospore mutant
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Presenter: |
Daniel, Patricia L., pld3@dana.ucc.nau.edu |
Authors | Daniel, Patricia L. (A) VanWinkle-Swift, Karen P (A) | | Affiliations: |
(A): Northern Arizona University
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The Chlamydomonas zygospore, produced as the end product of sexual reproduction, is remarkably resistant to abiotic stress and can serve as a useful model for identifying modes of resistance. In the homothallic species, C. monoica , recessive mutations affecting zygospore resistance will be expressed in the phenotype when "self-mating" occurs within clonal populations. Thus we have been able to identify many mutant strains carrying zygospore-specific mutations. Using fluorodeoxyuridine mutagenesis, we have obtained a mutant strain, D19, showing increased sensitivity to chloroform vapors, a treatment that is used routinely to kill vegetative cells and select for wildtype zygospores. The D19 strain also shows a marked increase in sensitivity to the lethal effects of ultraviolet radiation. Wildtype zygospores are protected by a massive, structurally complex secondary zygospore wall. The zygospore wall, which exhibits blue autofluorescence and contains a sporopollenin-like component, is resistant to degradation in boiling sulfuric acid/acetic anhydride (acetolysis). When viewed by fluorescence microscopy, D19 zygospores show greatly reduced autofluorescence. Furthermore, little residue and no intact walls are recovered after acetolysis of D19 zygospores. Scanning and transmission electron microscopy reveal abnormalities in surface architecture and discontinuities in the surface layer of the zygospore wall although a massive inner wall layer is still present. Crosses involving the D19 strain produce chloroform-resistant zygospores; thus the D19 mutation is recessive. In fifty tetrads analyzed, chloroform sensitivity, UV sensitivity, and reduced zygospore autofluorescence co-segregate, indicating that each results from the same Mendelian gene mutation.
