Research Interests

Plants are sessile organisms inherently displaying diverse arrays of metabolisms. Thousands of plant species have enormous potentials for the discoveries of novel pharma- and agro-chemicals. Many plant metabolic end-products today are not the results of random combinatorial chemical reactions but the results of many millions of years of functional selections that have in turn enabled plants to survive and flourish. For this reason, plant metabolites often exhibit biological functions. One class of secondary metabolite, called isoprenoids, is known to have many bio-activities. For examples, some conifer trees can synthesize a sesquiterpenoid called juvabione which perturbs normal insect development by mimicking juvenile hormone and thereby protecting trees from insect pests. Maize uses a sesquiterpenoid, caryophyllene, to call host-friendly nematodes which can kill pathogenic larvae, a major root-infecting agent in maize. From the human-health perspectives, some examples of plant-derived pharmaceuticals and nutraceuticals are diterpenoid taxol (anti-cancer drug from yew tree), tetraterpenoid lycopene (anti-oxidant from tomato), and sesquiterpenoid artemisinin (anti-malarial drug from sweet wormwood).
Basic rules of language that plant cells employ to communicate with surrounding physical and biological environments and between different cell-types and organelles have yet to be deciphered. Many of the fundamental principles dictating the carbon-flow of plant secondary metabolisms remain unknown. For example, we do not understand 1) the full spectrum of biosynthetic genes and enzymes responsible for the formation of complex biomolecules in plants, 2) how specific sets of genes are turned on and off in response to environmental signals and developmental cues, 3) how the efficient carbon-flow can be achieved in some specialized cell-types such as trichomes and laticifers in plants, 4) what structural motives of several supergene families (e.g., terpene synthase, methyl transferase, and cytochrome P450s) provide substrate specificities, and what we can learn from these natural enzymes for the rational design of novel enzymes, 5) what the ecophysiological roles of the plant secondary metabolites are.
The primary goal of my research is to understand the fundamental principles governing the biosynthesis and regulation of plant metabolisms. The secondary goal is to translate the knowledge obtained from the basic research to the agro- and pharma-sectors for desirable plant traits. Due to the rapid development in plant biology in recent years, it is routine to isolate genes for novel bio-catalysts by genomics approach, to accurately express those genes in targeted tissue-types by use of specific promoter, and to eliminate unwanted metabolic pathways by mutant screening or reverse genetics. Protein engineering by modeling or by in vitro evolution also helps design rational strategies for metabolic engineering. We are currently focusing on the study of a specific branch of plant secondary pathways called isoprenoid metabolism in the Compositae family, which constitutes >10% of all flowering plant species. My laboratory is taking full advantages of the multi-disciplinary approaches such as plant genomics, plant reverse genetics, cell biology, microbial metabolic engineering, and transcriptomics tools as well as classical biochemistry and genetics.

Courses Taught

Graduate Students

Selected publications

• Ikezawa, N., Göpfert, J.C., Nguyen, D.T., Kim, S.U., Paul E. O’Maille, Spring O., and Ro, D.K. Lettuce costunolide synthase (CYP71BL2) and its homolog (CYP71BL1) from sunflower catalyze distinct regio- and stereo-selective hydroxylations in sesquiterpene lactone metabolism. (2011) J. Biol. Chem. 286:21601-21611
• Barriuso, J., Nguyen, D.T., Li, J., Roberts, J., MacNevin, G., Chaytor, J. L., Marcus, S., Vederas, J., Ro, D.K. Double Oxidation of the Cyclic Nonaketide Dihydromonacolin L to Monacolin J by a Single Cytochrome P450 Monooxygenase, LovA. (2011) J. Am. Chem. Soc. 133: 8078-8081
• Nguyen DT, Göpfert JC, Ikezawa N, Macnevin G, Kathiresan M, Conrad J, Spring O, Ro DK. 2010. Biochemical conservation and evolution of germacrene A oxidase in Asteraceae. . J Biol Chem. 2010, 285:16588-98.
• Göpfert, J.C., MacNevin, G., Ro, D.K. and Spring O. (2009) Identification, functional characterization and developmental regulation of sesquiterpene synthases from sunflower capitate glandular trichomes. BMC Plant Biology. 9:86
• Ro DK, Ouellet M, Paradise EM, Burd H, Eng D, Paddon CJ, Newman JD, Keasling JD. Induction of multiple pleiotropic drug resistance genes in yeast engineered to produce an increased level of anti-malarial drug precursor, artemisinic acid. (2008) BMC Biotechnol. 8:83
• Chang, M.C.Y., Eachus, R.A., Trieu, W., Ro, D.K. and Keasling J.D. (2007) Engineering Escherichia coli for production of functionalized terpenoids using plant P450s. Nature Chemical Biology. 3: 274-277.
  
• Shiba, Y. Paradiase, E.M., Kirby, J., Ro, D.K., Keasling, J.D. (2007) Engineering of the pyruvate dehydrogenase bypass in Saccharomyces cerevisiae for high-level production of isoprenoids. Metabolic Engineering. 9: 160-168
  
• Ro, D.K., Paradise, E.M., Ouellet, M., Fisher, K.J., Newman, K.L., Ndungu, J.M., Chang, M.C.Y., Ham, T.S., Eachus, R.A., Ho, K.A., Shiba, Y., Sarpong, R., Keasling, J.D. (2006) Production of the anti-malarial drug precursor artemisinic acid in engineered yeast. Nature. 440: 940-943
  
• Ro, D.K. and Bohlmann, J. (2006) Diterpene resin acid biosynthesis in loblolly pine (Pinus taeda): Functional characterization of abietadiene/levopimaradiene synthase (PtTPS-LAS) cDNA and subcellular targeting of PtTPS-LAS and abietadienol/abietadienal oxidase (PtAO, CYP720B1). Phytochemistry. 67: 1572-1578
  
• Ro, D.K., Ehlting, J., Keeling, C.I., Lin, R., Mattheus, N, and Bohlmann, J. (2006) Microarray expression profiling and functional characterization of AtTPS genes: Duplicated Arabidopsis thaliana sesquiterpene synthase genes At4g13280 and At4g13300 encode root-specific and wound-inducible (Z)-<gamma>-bisabolene synthases. Arch. Biochem. Biophysics. 448: 104-116
  
• Ro, D.K., Arimura, G.I., Lau, S, Piers, E., and Bohlmann, J. (2005) Loblolly pine abietadienol/abietadienal oxidase PtAO (CYP720B1) is a multi-functional, multi-substrate cytochrome P450 monooxygenase. Proc. Nat. Acad. Sci. USA. 102: 8060-8065
  
• Chen, F., Ro, D.K., Petri, J., Gershenzon, J., Bohlmann, J., Pichersky, E., and Tholl, D. (2004) Characterization of a root-specific arabidopsis terpene synthase responsible for the formation of the volatile monoterpene 1,8-cineole. Plant Physiology. 135: 1956-1966
  
• Ro, D.K., and Douglas, C.J. (2004) Reconstitution of the entry point of plant phenylpropanoid metabolism in yeast (Saccharomyces cerevisiae): Implications for control of metabolic flux into the phenylpropanoid pathway. J. Biol. Chem. 279: 2600-2607
  
• Ro, D.K., Ehlting, J., and Douglas, C.J. (2002) Cloning, functional expression, and subcellular localization of multiple NADPH-cytochrome P450 reductases from hybrid poplar. Plant Physiology. 130: 1837-1851
  
• Ro, D.K., Mah, N., Ellis, B.E., and Douglas, C.J. (2001) Functional characterization and subcellular localization of poplar (Populus trichocarpa x Populus deltoides) cinnamate 4-hydroxylase. Plant Physiology. 126: 317-329