Title

Expression and Characterization of Gene Duplicates in Bacterial Endosymbiont Speciation

Presentation Type

Presentation

Abstract

The goal of my project is to investigate the process of genome reduction following speciation. We hypothesize that an apparently functional gene of an endosymbiont bacteria is in fact an incipient pseudogene. The long lifespan of cicadas has provided a unique opportunity to study the effects of genome reduction in endosymbiont bacteria. In the cicada Tettigades undata (TETUND), the endosymbiont Candidatus Hodgkinia lineage has split into two discrete genomic lineages, each isolated to distinct Hodgkinia cells. These two new genomes are smaller and have both lost genes compared with the single-genome ancestral Hodgkinia present in Τettigades ulnaria (TETULN). Interestingly, gene loss in metabolic contributions of the TETUND Hodgkinia, such as the synthesis of histidine, show interpathway complementation so that the ancestral genes encoded in Hodgkinia TETULN are retained on at least one of the new Hodgkinia TETUND genomes. As a result, the host cicada now relies on two species of Hodgkinia with a combined genome nearly twice the size of their single genome ancestor. Given the large number of pseudogenized genes in different states of degradation that Dr. John McCutcheon’s lab has observed in the TETUND genomes, some apparently functional genes may be incipient pseudogenes that have not yet acquired an inactivating substitution. To test this idea, I have cloned one of the histidine genes (HisB) for each the two TETUND lineages and the ancestral TETULN into the genome of E. Coli. I then induced expression of HisB in E. Coli and performed assays on the HisB proteins to determine if any are nonfunctional. This will provide evidence that this genomic reduction is following a pattern of interpathway complementation.

Category

Physical Sciences

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Apr 17th, 3:20 PM Apr 17th, 3:40 PM

Expression and Characterization of Gene Duplicates in Bacterial Endosymbiont Speciation

UC 330

The goal of my project is to investigate the process of genome reduction following speciation. We hypothesize that an apparently functional gene of an endosymbiont bacteria is in fact an incipient pseudogene. The long lifespan of cicadas has provided a unique opportunity to study the effects of genome reduction in endosymbiont bacteria. In the cicada Tettigades undata (TETUND), the endosymbiont Candidatus Hodgkinia lineage has split into two discrete genomic lineages, each isolated to distinct Hodgkinia cells. These two new genomes are smaller and have both lost genes compared with the single-genome ancestral Hodgkinia present in Τettigades ulnaria (TETULN). Interestingly, gene loss in metabolic contributions of the TETUND Hodgkinia, such as the synthesis of histidine, show interpathway complementation so that the ancestral genes encoded in Hodgkinia TETULN are retained on at least one of the new Hodgkinia TETUND genomes. As a result, the host cicada now relies on two species of Hodgkinia with a combined genome nearly twice the size of their single genome ancestor. Given the large number of pseudogenized genes in different states of degradation that Dr. John McCutcheon’s lab has observed in the TETUND genomes, some apparently functional genes may be incipient pseudogenes that have not yet acquired an inactivating substitution. To test this idea, I have cloned one of the histidine genes (HisB) for each the two TETUND lineages and the ancestral TETULN into the genome of E. Coli. I then induced expression of HisB in E. Coli and performed assays on the HisB proteins to determine if any are nonfunctional. This will provide evidence that this genomic reduction is following a pattern of interpathway complementation.