Exploring the Universal Drivers of Glycosome Evolution in Kinetoplastea

Abstract

Subcellular compartmentalization is a defining feature of eukaryotic cells, an organizational complexity that traces back to the earliest common ancestor of all present-day eukaryotes. Understanding various organelles’ origins and early evolutionary stages remains a significant challenge. Organellar proteomes are shaped by controlled pathways that guide cytosol-produced proteins to their designated subcellular locales. The specific routing of these proteins can differ across varying physiological states, cell types, and evolutionary lineages. In eukaryotes, evolutionary retargeting—the process where the subcellular destination of a protein changes through evolutionary time—has been widespread and can involve any combination of organelles, complicating efforts to trace back and reconstruct the evolutionary history of organelles. This dissertation investigates the evolution of glycosomes, peroxisome-related organelles in kinetoplastids and diplonemids. Chapter 1 introduces the key concepts of kinetoplastids, glycosomes, and the test organisms used throughout the dissertation. Chapter 2 conducts an in-silico comparison of proteomic data from available organisms and transcriptomic data from other kinetoplastids, using glycosomal targeting sequences. Chapters 3 and 4 explore the factors driving protein compartmentalization within glycosomes, examining the effects of glucose and nutrient replenishment in Chapter 3, and hypoxia in Chapter 4. Chapter 5 presents a detailed study of PIP39, a glycosomally localized protein phosphatase in Leptomonas seymouri, highlighting its role in the oxidative stress response. The dissertation concludes with a summary of the major findings, a discussion of the limitations, and future research directions. This work significantly advances our understanding of metabolic pathway compartmentalization and elucidates specific molecular mechanisms that sustain enzymatic pathways within glycosomes. Furthermore, it establishes the glycosome as a uniquely defined and pedagogically useful system to demonstrate how selection influences the interplay between existing organizational structures and environmental stimuli, fostering adaptive evolution.