How horizontal gene transfer occurs from the time scale of molecular events to the evolution

Junichi Obokata

Graduate School of Life and Environmental Sciences, Kyoto Prefectural University

Functional gene transfers between the organisms or organelles have greatly contributed to the evolutionary innovation and diversification. However, we still have little knowledge about the molecular basis of these phenomena. How do the transferred gene sequences become transcriptionally active and functional in the alien genome environment? In this talk, I try to illustrate how HGT/EGT occurs from the time scale of molecular events to the evolutionary outcome, based on the studies of our research group, with special emphasis on two topics.

The first topic concerns the mechanism by which newly translocated gene sequences acquire transcriptional competence in the eukaryotic nuclear genome. To address this question, we attempted to simulate this process by the massive gene-trapping experiments using plant cultured cells and introduced promoter-less marker genes. Bioinformatic analysis of their transcription profiles suggests that the chromatin remodeling concomitant with the gene insertion event should be the key step to cause the de novo transcription of the marker sequences. The second topic is how HGT and EGT occur and cause genome shuffling in the early process of endosymbiotic evolution, which insight was derived from the genome analysis of a thecate amoeba containing a unique photosynthetic organelle distinct from chloroplasts. The analysis data suggest that the HGT/EGT as well as the genome shuffling between the symbiont and host should proceed far faster than we previously thought, implying some unexpected factor may be involved in causing this rapid shuffling. Based on the introduction of these topics, we would like to discuss about how HGT/EGT occurs, as well as the essential properties of the eukaryotic genome which enabling HGT/EGT.