Alternative Title

On the hunt for silicon transporter homologs

Publication Date

2019

Document Type

Honors Project

Degree Name

Bachelor of Arts

Department

Biological Sciences

Advisors

Laura A. Katz

Keywords

Testate amoebae, Arcellinida, Silicon transporter, Genome content, Biosililcification, Lsi2, Single-cell transcirptomics, Genomics, Transmembrane protein, Homology, Bioinformatics

Abstract

The Arcellinida are an understudied clade of unicellular amoebae, characterised by their single-chambered shells and their use of extensions of their cytoplasm, pseudopodia, for locomotion. The shells of the Arcellinida are self-secreted and display a significant diversity in composition, morphology, and size. Two classes of Arcellinid testate amoebae build glass-like silica shells of great complexity, adorned with meticulously constructed geometrical silica structures that they synthesise de novo in their cytoplasm. To think a mere speck of cytoplasm, void of limbs or brain and universally considered among the simplest of life forms, the architect of microscopic structures of remarkable beauty, begs the question if a single cell can be intelligent as it appears capable of navigating its micro-landscape with a sense of purposeful intentionality. Furthermore, the mechanisms that drive shell-building in the Arcellinida are not known. The generalized pathway for forming biological silica structures starts with the uptake of silica from the surrounding aquatic environment, the subsequent transportation of it into the cytoplasm, and finally the concentration of it in the Golgi complex. The transport of extracellular silica across the plasma membrane requires silicon-interacting transmembrane proteins, silicon ransporters, which have an ancient origin. In this study, I focus on uncovering the molecular mechanisms that drive the transport of silica from the extracellular environment and into the cytoplasm. I use a combination of molecular techniques and bioinformatic tools to examine the genome content of Lesquereusia spiralis and Quadrulella symmetrica , two Arcellinid testate amoebae with silica shells, to determine candidate genes for silicon transport. The transcriptome (high throughput sequence; HTS) data suggests that the Arcellinida have genes that are homologous to silicon transporters identified in other lineages. Moreover, this is the first study of its kind, which both examines the molecular machinery that allows Arcellinid testate amoebae to build silica shells and proposes candidate genes for silicon transport, the function that may allow for this ability. In addition, the Arcellinida can teach us about the molecular evolution of silicon transport, which is of great importance both in light of the development of models for silicon biotechnology and because of the crucial role the Arcellinida play in the global biogeochemical cycling of silicon.

Rights

©2019 Emma Gabrielle Östlund-Sholars. Access limited to the Smith College community and other researchers while on campus. Smith College community members also may access from off-campus using a Smith College log-in. Other off-campus researchers may request a copy through Interlibrary Loan for personal use.

Language

English

Comments

89 pages : color illustrations. Includes bibliographical references (pages 67,-70, 86-88)

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