Abstract 1322 Exploring the Diversity of Diterpene Synthases in Rice

Cultivated rice (Oryza sativa) is a staple food crop and a model cereal plant, providing nearly 30% of the world's consumed calories. It produces a great number of secondary metabolites, particularly labdane-related diterpenoids, which serve as a chemical defense system for the grain to protect itself from external threats. These compounds serve various functions in defense against microbial pathogens. Labdane-related diterpenoids are initially formed by Class II and Class I diterpene synthases, termed copalyl diphosphate synthases (CPSs) and kaurene synthase-like (KSLs), and their products then modified by cytochromes P450 (CYPs). In our research, we found significant variation in the biochemical activity of orthologous KSLs between different cultivars of rice. The variation leads to alternative pathways in different rice cultivars, with subsequent difference in natural product production. We explore the differences and relationships between functionally distinct orthologous KSLs and the effect on rice's arsenal of natural products and their ability to defend against threats. Additionally, we look to find single nucleotide switches to alter functions of these closely related KSLs, allowing genetic engineering for rice to produce alternative phytoalexins, potentially enabling increased protection from various threats. Thanks for Grants from the USDA (2020-67013-32557) to R.J.P.