Full text
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| Author(s): |
Paulo Gonzalez Hofstatter
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Instituto de Biociências (IBIOC/SB) |
| Defense date: | 2019-08-14 |
| Examining board members: |
Daniel José Galafasse Lahr;
Sergio Russo Matioli;
Enrique Lara Pandi
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| Advisor: | Daniel José Galafasse Lahr |
| Abstract | |
Sex is an inherent part of eukaryotic life. Far from the common sense, sex can be defined as plasmogamy (cell fusion) eventually followed by meiosis. Both processes are fundamental to any sexual life cycle and require a specific machinery. Several components of this machinery have been already identified and remain highly conserved among the most distantly related eukaryotic lineages, performing basically the same functions in all groups. This meiosis toolkit may be used as an indication of sexual processes, even when such processes have not been observed yet. Even though the ancestor of all eukaryotes is assumed to be sexual, some eukaryotic groups are normally treated as asexuals by many authors in the literature based on the lack of observable sexual cycles in culture. Among these \'asexuals\' are the amoebae belonging to Amoebozoa, a major eukaryotic supergroup. Several lineages of Amoebozoa are considered asexual, but some well studied genera inside this supergroup were demonstrated to be fully sexual, i.e., Trichosphaerium, Physarum, Dictyostelium. Some other genera exhibit indirect evidence for sexual processes and may be sexual as well. The occurrence of sexual organisms inside Amoebozoa points to a sexual ancestor for the whole supergroup, otherwise sex would have to evolve again in Amoebozoa, not exactly a parsimonious view. We collected molecular data from several amoebozoan lineages with representatives of most of its known diversity and searched for an expanded meiosis toolkit, adding the plasmogamy machinery to it. As a result, we were able to find every component of this machinery in basically all amoebozoan groups. These results support not only the occurrence of sexual processes in all Amoebozoa, but also a probable high level of conservation for mains sexual processes. Additionally, we performed similar analyses for all known eukaryotic diversity with similar results, except for a few isolated groups. Deep reconstructions also provided evidence for a new evolutionary history for the mismatch-repair system in eukaryotes, a DNA repair mechanism that is part of the meiotic machinery. All results point to an archaeal origin for the meiotic machinery and for a widespread presence of sexual processes in basically all eukaryotes (AU) | |
| FAPESP's process: | 15/06306-0 - Evolution of meiosis and sex in Amoebozoa |
| Grantee: | Paulo Gonzalez Hofstatter |
| Support Opportunities: | Scholarships in Brazil - Doctorate |