TOWARDS UNDERSTANDING DIRIGENT PROTEIN FUNCTION
Seneviratne, Herana Kamal
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Plants produce a dazzling collection of chemical compounds with great structural and functional diversity that are known as specialized metabolites which have important roles in plant defense responses. Most significantly, these chemical entities serve as rich and important source of biologically active pharmaceuticals. Although much has been known about the immense importance of these specialized metabolites, little is known about how they are produced in plants. The evolution of the biochemistry of vascular plants depend extensively upon unique phenoxy radical-radical coupling reactions to produce different chemical compounds. In this regard, a group of proteins called dirigent proteins (DPs) control the stereoselectivities of above-mentioned coupling processes to engender a class of specialized metabolites known as lignans. In particular, lignans represent a large class of plant specialized metabolites which exhibit a broad range of physiological functions and potential medicinally important therapeutic properties. Even though there are many dirigent homologs in the plant kingdom, we do not know the precise functions of these homologous proteins. This dissertation describes the elucidation of the biochemical function of a dirigent homolog, i.e. PsDRR206 and localization of phytoalexin pathway in pea (Pisum sativum) pods using high-resolution mass spectrometry techniques. From the studies described herein, the metabolite associated with PsDRR206 gene was identified as pinoresinol monoglucoside. Additionally, the localization of selected phytoalexins including pinoresinol monoglucoside as well as (+)-pisatin was determined as the endocarp epidermal cell layer of pea pod tissue. The results from these studies provide new insights for plant biochemistry research through gaining the knowledge of important biological processes occurring in nature.