This thesis describes the stepwise evolution of a functional seed peptide called Sunflower Trypsin Inhibitor-1 (SFTI-1). SFTI-1 originates within the coding sequence of the seed albumin PawS1 and uses the same processing enzyme, asparanginyl endopeptidase for maturation (Mylne, et al., 2011). This enzyme has evolved to cleave a tail peptide from precursors and couple to a transpeptidation reaction to make macrocyclic peptides (Bernath-Levin, et al., 2015). Using de novo transcriptomics (Jayasena, et al., 2014) I traced the evolution of PawS1. The progenitor of PawS1 is a normal albumin which was interrupted by a genetic insertion ̴45 million years ago to create the ancestral PawS-Like (PawL1) genes (Elliott, et al., 2014) that encode Cys-less macrocycles. PawL1 further evolved to yield bicyclic peptides and acquire a biological function. The seed storage role of PawS1 in sunflower is little, explaining how PawS1 had the freedom to evolve buried peptides (Jayasena, et al., 2016).
|Qualification||Doctor of Philosophy|
|Award date||13 Jul 2016|
|Publication status||Unpublished - 2015|