Exploring Ancient Plant Metabolism: Resurrection and Characterization of a Sabath Methyltransferase from the 475-Million-Year-Old Land Plant Ancestor

Date of Award


Degree Name

Master of Science


Biological Sciences

First Advisor

Dr. Todd Barkman

Second Advisor

Dr. Yan Lu

Third Advisor

Dr. Jian Yao


Molecular evolution, SABATH methyltransferase, ancestral reconstruction, plant metabolism, phylogenetic analysis

Access Setting

Masters Thesis-Abstract Only

Restricted to Campus until



One of the fundamental goals of evolutionary biology is understanding how protein function and structure have evolved over time to produce the diversity of life observed in the present day. Widely regarded as one of the drivers of this diversity is the occurrence of gene duplication events. The SABATH family of methyltransferases are critical to many components of plant specialized metabolism and have developed diverse substrate preferences and activities through several gene duplication events. Prior phylogenies demonstrating the evolutionary history of this family have been generated using small datasets; however, this risks the exclusion of sequences from underrepresented groups of land plant lineages. By generating the largest, most comprehensive phylogeny of the SABATH methyltransferases to date, this study explored the evolutionary history of this family. In doing so, it was determined that the first land plants that emerged ca. 475mya likely only possessed one SABATH gene. Using a powerful tool known as ancestral sequence reconstruction (ASR), this ancestral gene was resurrected and functionally characterized. The putative SABATH ancestor was revealed to have promiscuous catalytic activity, providing evidence that although the first land plants were likely more genetically limited than their descendants, they were capable of achieving metabolic complexity.

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