Lateral gene transfer and the evolution of photosynthesis in eukaryotes

Abstract

Photosynthetic eukaryotes comprise the most visible and massive fraction of the biosphere. They have contributed to shaping land, oceans, and atmosphere during the last 2 billion years and their influence dominates every aspect of the existence of the rest of living beings, humans included. The introduction of photosynthesis into the eukaryotic domain and subsequent spread through various lineages by an endosymbiotic process are well-established facts, but the details implicated in allowing and driving the process remain under scrutiny. Relocation of genes from the intracellular symbiont into the host genome is critical to the origin of organelles by endosymbiosis, and an increasingly large body of evidence indicates that acquisition of genes from external sources can influence the organelle function to a large extent. In this chapter, we discuss the roles of gene transfer on the origins, evolution, and function of photosynthetic organelles in a wide range of eukaryotic organisms. A comprehensive review of recent studies devoted to elucidating the mechanisms involved in the migration of genes from endosymbiont to host nucleus is presented. In addition, we also mention the current controversies and recognize the difficulties faced by investigators working on this fascinating field. Finally, we identify several promising research questions that are likely to shed new light on our understanding of how gene flux has and does impact the evolution of photosynthetic eukaryotes.