LLGs, CrRLK1Ls, and Plant Reproduction: An Evolutionary Perspective on Reproductive Signaling in Angiosperms

Abstract

Gene family evolution, often driven by duplication events, presents opportunities for organisms to undergo diverse evolutionary paths, acquiring various functions and traits. The model plant, Arabidopsis thaliana, has a crucial signaling complex involving three gene families—LLG, CrRLK1L, and RALF—that plays a systemic role in regulating growth, development, and reproduction. Despite extensive research on the molecular functions of this complex in A. thaliana, gaps persist in understanding its evolutionary history and conservation across other plant species. This dissertation addresses these gaps by exploring the evolution and conservation of the LLG-CrRLK1L-RALF tripartite complex across angiosperms. The results in the three chapters detail the evolutionary dynamics and functional conservation of these family members with an emphasis on their roles in reproduction. The first chapter explores the evolution of the LLG family, revealing lineage-specific events contributing to their diversity in angiosperms. Regulatory subfunctionalization is identified as a key factor in the retention of A. thaliana LLGs, with expression analyses suggesting a conserved ancestral role in pollen tube growth across angiosperms. The second chapter focuses on the CrRLK1L family, providing a comprehensive evolutionary perspective by characterizing clades, identifying motifs, and revealing a conserved role in pollen tube growth. The third chapter investigates the functional conservation of this system in pollen tube growth within eudicots using the CrRLK1L, BUPS. Taken together, the three chapters contribute to a holistic understanding of the evolutionary history and functional conservation of crucial gene families involved in plant reproductive processes.