Minisymposium 5: Secondary Metabolism

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Abs # M0501: Identifying and Characterizing Rice Terpene Synthase Genes Involved in Insect Defense Using An Integrated Functional Genomic Approach

Presenter:	Yuan, Joshua S       Contact Presenter
Authors	Yuan, Joshua S (A)   Adamczyk, John  (B)   Gwinn, Kimberly D (C)   Chen, Feng  (A)
Affiliations:	(A): Department of Plant Sciences, University of Tennessee, 2431 Joe Johnson Drive, Knoxville, TN 37996 (B): USDA-ARS, Southern Insect Management Research Unit, Stoneville, MS 38776 (C): Department of Entomology and Plant Pathology, University of Tennessee, 2431 Joe Johnson Drive, Knoxville, TN 37996

Terpenoids are the most prevalent and diverse class of plant secondary metabolites involved in a variety of biological and ecological functions. The rice genome contains 48 TPS-like sequences, some of which have been characterized to be diterpene synthase. The biochemical and biological functions of the majority of the rice TPS genes remain unknown. In this project, we employ an integrated functional genomic approach that combines bioinformatics, expression profiling, metabolic profiling and biochemistry to systemically identify and characterize the rice TPS genes involved in plant defense against insect herbivores. Using rice fall armyworm (Spodoptera frugiperda) as an insect model, we first analyzed global gene expression changes of rice plants under herbivory using microarray, and identified nine herbivore-induced TPS genes. We then took a biochemical approach to determine the biochemical function of the herbivore-induced TPS genes. Here we report the biochemical activity for two genes, OsTPS3 and OsTPS42. OsTPS3 has activity with GPP to produce linalool. OsTPS42 is a sesquiterpene synthase. It uses FPP as substrate to produce multiple sesquiterpene with beta-caryophyllene the predominant. To verify the in vivo activity of OsTPS3 and OsTPS42, we analyzed volatile profile of rice plants infested with rice fall armyworms. Both linalool and beta-caryophyllene are significantly induced, indicating they are the products of OsTPS3 and OsTPS42, respectively. The herbivore-induced terpenoids may either function as toxins to directly ward off herbivores or act as volatile signals to attract the natural enemy of the herbivores. The identification of TPSs for the production of these herbivore-induced terpenoids provides good opportunities to address these questions.