Hiroshi Maeda, PhD

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Contents

Contact Information

  • Purdue University
  • 625 Agriculture Mall Dr., Horticulture Build., West Lafayette, IN 47907 U.S.A.
  • Phone: +1-765-496-6268, Email: hmaeda@purdue.edu

Professional Experience

Education

  • 2006 PhD, Michigan State University, Cell and Molecular Biology Program and DOE-Plant Research Laboratory, Dean DellaPenna Laboratory
  • 2001 MS, Osaka University, Biotechnology, Dr. Akio Kobayashi Laboratory
  • 1999 BS, Osaka University, Biotechnology, Dr. Akio Kobayashi Laboratory

Research Interests

  • As sessile organisms, plants produce a tremendous array of organic compounds using CO2, underground nutrients, and sunlight energy to survive in challenging ecological niches. This plant chemical diversity is achieved by the diversification of plant metabolic pathways far beyond central metabolism. Although extensive efforts are currently being made to understand these plant-specific metabolic pathways, we still have a limited knowledge of how plants allocate available carbon, fixed by photosynthesis, to a variety of downstream metabolic pathways. This fundamental knowledge gap also creates a bottleneck in effective plant breeding and metabolic engineering for the improved production of targeted metabolites. To address this issue, my research focuses on understanding the biosynthetic pathways and regulatory mechanisms of plant primary metabolism, specifically the shikimate and phenylalanine pathways, which direct 30% of photosynthetically fixed carbon to the production of plant phenolic compounds including lignin.
2011 Gordon Research Seminar on Plant Metabolic Engineering
2011 Gordon Research Seminar on Plant Metabolic Engineering

Current/Past Research Projects

  • Phenylalanine Biosynthesis and Its Regulation in Plants (2007 to present, Dudareva Lab)
Fig.1 Plant phenylalanine biosynthesis
Fig.1 Plant phenylalanine biosynthesis

Phenylalanine is an essential aromatic amino acid in human diets but also a precursor of numerous plant-derived phenolic compounds, which play crucial roles in plant growth, development, and environmental responses. Despite its importance in both plant and human physiology and metabolism, our knowledge of phenylalanine biosynthesis and its regulation in plants remains fragmented. My research combined functional genomic, bioinformatic, and biochemical approaches to identify prephenate aminotransferase (PPA-AT) and arogenate dehydratase (ADT), which are involved in the final two steps of phenylalanine biosynthesis [1,2](Fig. 1). These discoveries completed the identification of genes encoding enzymes for phenylalanine biosynthesis in plants. RNAi suppression of the ADT gene in petunia flowers, which produce high levels of phenylalanine and phenylalanine-derived volatiles, provided the first genetic evidence that, unlike in most microorganisms, phenylalanine biosynthesis in plants predominantly operates via the arogenate pathway [2]. Moreover, through isotope labeling studies and by developing LC/MS-based detection methods for trace pathway intermediates (i.e., prephenate, arogenate), we discovered the presence of a novel negative regulation of the flux through the shikimate pathway leading to phenylalanine biosynthesis [2](Fig. 1).

  • Tocopherol (vitamin E) Biosynthesis and Functions in Photosynthetic Organisms (2001 to 2007, DellaPenna Lab)
Fig. 2 Aniline blue callose staining of the vte2 mutant
Fig. 2 Aniline blue callose staining of the vte2 mutant

Tocopherols are the major class of lipid soluble antioxidants that are collectively known as vitamin E and essential nutrients in human diets. These antioxidants are produced only in photosynthetic organisms, including all plants and algae, and most cyanobacteria. However, the biosynthetic pathway and the functions of tocopherols were not fully understood in these organisms. I was initially involved in a map-based cloning of tocopherol biosynthetic enzyme, 2-methyl-6-phytyl benzoquinol (MPBQ) methyltransferease, which uncovered the convergent evolution of the methyltransferase in plants and cyanobacteria [11]. My research then focused on elucidation of tocopherol functions in photosynthetic organisms using vitamin e-deficient (vte) mutants of Arabidopsis thaliana and Synechocystis sp. PCC6803, a model photosynthetic eukaryote and prokaryote, respectively. Detailed analyses of their physiological, biochemical, and cellular responses defined a novel cell-type specific function of tocopherols in source-to-sink carbohydrate transport via phloem parenchyma transfer cells [8](Fig. 2). Detailed lipid profiling analyses and the identification of second site mutations suppressing the mutant phenotype further uncovered that plastid-synthesized tocopherols modulate polyunsaturated fatty acids in extra-plastidic membranes [3,5].

Publications

  1. Maeda H., Yoo H., and Dudareva N. (2011) Prephenate Aminotransferase Directs Plant Phenylalanine Biosynthesis via Arogenate. Nature Chem. Biol., DOI:10.1038/nchembio.485
  2. Maeda H., Shasany A.K., Schnepp J., Orlova1 I., Taguchi G., Cooper B.R., Rhodes D., Pichersky E. and Dudareva N. (2010) RNAi Suppression of Arogenate Dehydratase1 Reveals That Phenylalanine Is Synthesized Predominantly via the Arogenate Pathway in Petunia Petals. Plant Cell 22, 832-849 *Described as a Research Highlight in Nature Chemical Biology 6, 310
  3. Song W., Maeda H., and DellaPenna D. (2010) Mutations of the ER to plastid lipid transporters (TGD1, 2, 3 and 4) and the ER oleate desaturase (FAD2) suppress the low temperature-induced phenotype of Arabidopsis tocopherol deficient mutant vte2. Plant J. 62, 1004-1018
  4. Orlova I., Nagegowda D.A., Kish C.M., Gutensohn M., Maeda H., Varbanova M., Fridman E., Yamaguchi S., Hanada A., Kamiya Y., Krichevsky A., Citovsky V., Pichersky E., and Dudareva N. (2009) The Small Subunit Snapdragon Geranyl Diphosphate Synthase Modifies the Chain Length Specificity of Tobacco Geranylgeranyl Diphosphate Synthase in Planta. Plant Cell 21, 4002-4017
  5. Maeda H., Sage T.L., Isaac G.., Welti R., and DellaPenna D. (2008) Tocopherols Modulate Extra-Plastidic Polyunsaturated Fatty Acid Metabolism in Arabidopsis at Low Temperature. Plant Cell 20, 452-470 *Described in the Featured Article of the issue Plant Cell 20, 246
  6. Maeda H. and DellaPenna D. (2007) Tocopherol Functions in Photosynthetic Organisms. Curr. Opin. Plant Biol. 10, 260-265
  7. Maeda H., Song W., Sage T.L. and DellaPenna D. (2007) Tocopherols Play a Limited Role in Photoprotection but a Crucial Role in Chilling Adaptation in Arabidopsis Leaves. In Current Advances in the Biochemistry and Cell Biology of Plant Lipids, C. Benning and J. Ohlrogge, eds (Aardvark Global Publishing Company, LLC, Salt Lake City, UT), pp. 112-115 PDF download (4.5 MB)
  8. Maeda H., Song W., Sage T.L. and DellaPenna D. (2006) Tocopherols Play a Crucial Role in Low Temperature Adaptation and Phloem Loading in Arabidopsis. Plant Cell 18, 2710-2732 *Highlighted on the Cover of the issue.
  9. Sakuragi Y., Maeda H., DellaPenna D. and Bryant D.A. (2006) α-Tocopherol Plays a Role in Photosynthesis and Macronutrient Homeostasis of the Cyanobacterium Synechocystis sp. PCC 6803 That is Independent of its Antioxidant Function. Plant Physiol. 141, 508-521
  10. Maeda H., Sakuragi Y., Bryant D.A., and DellaPenna D. (2005) Tocopherols Protect Synechocystis sp. Strain PCC 6803 from Lipid Peroxidation. Plant Physiol. 138, 1422-1435
  11. Cheng Z., Sattler S., Maeda H., Sakuragi Y., Bryant D.A., and DellaPenna D. (2003) Highly Divergent Methyltransferases Catalyze a Conserved Reaction in Tocopherol and Plastoquinone Synthesis in Cyanobacteria and Photosynthetic Eukaryotes. Plant Cell 15, 2343-2356
  12. Okazawa A., Maeda H., Fukusaki E., Katakura Y., and Kobayashi A. (2000) In Vitro Selection of Hematoporphyrin Binding DNA Aptamers. Bioorg. Med. Chem. Lett. 10, 2653-2656
  13. Fukusaki E., Kato T., Maeda H., Kawazoe N., Ito Y., Okazawa A., Kajiyama S. and Kobayashi A. (2000) DNA Aptamers that Bind to Chitin. Bioorg. Med. Chem. Lett. 10, 423-425

Awards and Fellowships

  • Fellowships
    • 2008-2010, Postdoctoral Fellowship for Research Abroad from Japan Society for the Promotion of Science (JSPS)
    • 2006, Dissertation Completion Fellowship from MSU College of Natural Science
    • 2006, Travel grant for attending the annual meeting of the American Society of Plant Biologists (ASPB)
    • 2001-2003, Graduate Research Assistantship from DOE-Plant Research Laboratory (PRL)
  • Awards
    • 2011, Eric E. Conn Young Investigator Award of the American Society of Plant Biologists
    • 2009, Best poster award at the 2009 Gordon Research Conference on Plant Metabolic Engineering
    • 2006, Anton Lang Memorial Graduate Student Award of DOE-Plant Research Laboratory
    • 2006, Best oral presentation award at MSU Plant Science Graduate Student Symposium
    • 2000, Poster prize at 78th national meeting of the Chemical Society of Japan

Professional Activities

  • 2011, Chair of the 2011 Gordon Research Seminar on Plant Metabolic Engineering
  • 2011-present, Review Editor of Frontiers in Plant Physiology
  • 2006-present, Reviewer for Plant Physiology, Plant Cell and Physiology, Planta, Journal of Experimental Botany, Molecular Plant, New Phytologist, Plant Biology, Plant Cell Reports
  • 2004-present, Co-reviewer for The Plant Cell, Plant Physiology, Plant Journal
  • 2008-2010, Initiating and organizing the Plant Biology Student/Postdoc Seminar Series at Purdue University
  • 2009, A member of organizing committee for Purdue Horticulture Departmental Retreat
  • 2004-2005, Seminar committee at DOE-Plant Research Laboratory, Michigan State University
  • 2003-2004, Personal affair committee at MSU DOE-Plant Research Laboratory, Michigan State University

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