Office: Biology 444
Phone: (970) 491-6614
Education
- Ph.D., UC Berkeley
About
Although plants are photoautotrophic organisms, they are composed of many heterotrophic tissue systems, such as roots, flowers, seeds, and developing leaves, that depend on carbon and nitrogen import for growth and development. In general, sucrose and amino acids are transported to the heterotrophic cells from mature leaves. This process is known as assimilate partitioning and it is a fundamental activity that allows plants to function as multicellular organisms. My laboratory provided the first biochemical and molecular descriptions of several plant sugar and amino acid transport systems that are key contributors to resource allocation within cells and between organs. We initially described these transporters using an in vitro biochemical assay that allowed us to define the transport properties and bioenergetics of these important carriers. To identify the genes encoding the plant's sugar and amino transporters, we used functional complementation of yeast transport mutants with plant cDNA expression libraries (PNAS 90:7441-7445). The yeast system is very useful because it allows us measure key transport properties and protein structure/function relationships when plant transport proteins expressed in yeast cells (PNAS 95:9025-9030). The unifying theme of our research today is understanding how plants regulate resource allocation between "source and sink" tissues. To tackle this complex question, we are using genetic and biochemical strategies to identify the signal transduction pathways that regulate assimilate partitioning. We discovered a unique sucrose-mediated signal transduction pathway that regulates the expression and protein abundance of the sucrose transporter that is responsible for phloem loading (PNAS 95:4784-4788; PNAS 99:10876-10880). We also discovered that multiple nitrogen-metabolites regulate amino acid transporter gene expression, and have now focused on understanding nitrate as a signal molecule that regulates unique patterns of plant gene expression. That research led to the discovery of a novel protein that appears to regulate cell wall structure (Plant Phys 152: 904-917, 2010). In a complementary biofuels research project, we are using genetic and genomic tools in rice as a model plant to identify genes that control primary productivity (biomass per m2). As part of that work, we discoved a unique transcription factor, that when exressed out of its normal context, increases yield by 3-fold! We're currently focused on understanding the underlying molecular mechanism.
Publications
- Field-based high throughput phenotyping rapidly identifies genomic regions controlling yield components in rice. Scientific Reports, 2017.
- Intronic Sequence Regulates Sugar-Dependent Expression of Arabidopsis thaliana Production of Anthocyanin Pigment-1/MYB75 PLOS ONE, 6, 2016.
- Cell Wall Composition and Bioenergy Potential of Rice Straw Tissues Are Influenced by Environment, Tissue Type, and Genotype BioEnergy Research, 2015.
- Transgenic approaches to altering carbon and nitrogen partitioning in whole plants: assessing the potential to improve crop yields and nutritional quality FRONTIERS IN PLANT SCIENCE, 2015.
- Plant phylogenetics and molecular genetics in the new era of genomics: commentary on the first special issue of the Turkish Journal of Botany. Turk. J. Bot. , 2014.
- Transport proteins in plant growth and development.Sugarcane: Physiology, Biochemistry and Functional Biology Wiley Publishing, 2013.
- Dissecting the Role of CHITINASE-LIKE1 in Nitrate-Dependent Changes in Root Architecture PLANT PHYSIOLOGY, 3, 2011.
- Carbohydrate Export from the Leaf: A Highly Regulated Process and Target to Enhance Photosynthesis and Productivity PLANT PHYSIOLOGY, 1, 2011.
- Genetic variation in biomass traits among 20 diverse rice varieties. Plant physiology, 1, 2011.
- Theoretical Maximum Algal Oil Production BIOENERGY RESEARCH, 2, SI, 2010.
- Chitinase-Like Protein CTL1 Plays a Role in Altering Root System Architecture in Response to Multiple Environmental Conditions PLANT PHYSIOLOGY, 2, 2010.
- Overlook agricultural research at our peril PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 38, 2009.
- Salicylic Acid Transport in Ricinus communis Involves a pH-Dependent Carrier System in Addition to Diffusion PLANT PHYSIOLOGY, 4, 2009.
- BAT1, a bidirectional amino acid transporter in Arabidopsis PLANTA, 5, 2009.
- Translational genomics for bioenergy production: There’s room for more than one model PLANT CELL, 10, 2007.
- Translational genomics for bioenergy production: there's room for more than one model. The Plant cell, 10, 2007.
- Expression and transcriptional regulation of amino acid transporters in plants AMINO ACIDS, 2, 2006.
- The bifunctional role of hexokinase in metabolism and glucose signaling PLANT CELL, 11, 2003.
- Protein phosphorylation plays a key role in sucrose-mediated transcriptional regulation of a phloem-specific proton-sucrose symporter PLANTA, 3, 2003.
- Sucrose-mediated transcriptional regulation of sucrose symporter activity in the phloem PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 16, 2002.
- ANT1, an aromatic and neutral amino acid transporter in Arabidopsis PLANT PHYSIOLOGY, 4, 2001.
- Nitrogen and carbon nutrient and metabolite signaling in plants PLANT PHYSIOLOGY, 1, 2001.
- Amino acid transporters in plants BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES, 1-2, 2000.
- Sucrose is a signal molecule in a new signal-transduction pathway that modulates sucrose transport activity and assimilate partitioning.AMERICAN SOCIETY OF SUGAR BEET TECHNOLOGISTS, PROCEEDINGS1999.
- Identification and characterization of plant transporters using heterologous expression systems JOURNAL OF EXPERIMENTAL BOTANY, SI, 1999.
- Sugar transporters in plant biology CURRENT OPINION IN PLANT BIOLOGY, 3, 1999.
- Sucrose is a signal molecule in assimilate partitioning (vol 95, 4784, 1998) PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 23, 1998.
- His-65 in the proton-sucrose symporter is an essential amino acid whose modification with site-directed mutagenesis increases transport activity PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 15, 1998.
- Sucrose is a signal molecule in assimilate partitioning PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 8, 1998.
- Plant feeding site selection on soybean by the facultatively phytophagous predator Orius insidiosus ENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, 2, 1998.
- LHT1, a lysine- and histidine-specific amino acid transporter in Arabidopsis PLANT PHYSIOLOGY, 3, 1997.
- Sec-independent protein translocation by the maize Hcf106 protein SCIENCE, 5342, 1997.
- Topology of NAT2, a prototypical example of a new family of amino acid transporters JOURNAL OF BIOLOGICAL CHEMISTRY, 48, 1997.
- Cloning and functional expression in oocytes of the sugar beet proton-sucrose symporter. PLANT PHYSIOLOGY, 3, S, 1997.
- Effect of chlorsulfuron on sucrose transport in leaf discs and plasma membrane vesicles isolated from sugar beet leaves. PLANT PHYSIOLOGY, 3, S, 1997.
- Membrane topology of a neutral amino acid transporter (NAT2/AAP1) from Arabidopsis thaliana. PLANT PHYSIOLOGY, 3, S, 1997.
- Site-directed mutagenesis of His71 in the proton-sucrose symporter. PLANT PHYSIOLOGY, 3, S, 1997.
- Molecular analysis of plant sugar and amino acid transporters JOURNAL OF EXPERIMENTAL BOTANY, SI, 1996.
- Cloning a lysine amino acid transporter PLANT PHYSIOLOGY, 2, S, 1996.
- Cloning the proton-sucrose symporter from sugar beet PLANT PHYSIOLOGY, 2, S, 1996.
- Molecular analysis of amino acid transporter structure and function PLANT PHYSIOLOGY, 2, S, 1996.
- Molecular cloning, immunochemical localization to the vacuole, and expression in transgenic yeast and tobacco of a putative sugar transporter from sugar beet PLANT PHYSIOLOGY, 2, 1996.
- Kinetics and specificity of a H+ amino acid transporter from Arabidopsis thaliana JOURNAL OF BIOLOGICAL CHEMISTRY, 4, 1996.
- Sucrose transporters in assimilate partitioning and plant growthSUCROSE METABOLISM, BIOCHEMISTRY, PHYSIOLOGY AND MOLECULAR BIOLOGY1995.
- SURFACTANT-INCREASED GLYPHOSATE UPTAKE INTO PLASMA-MEMBRANE VESICLES ISOLATED FROM COMMON LAMBSQUARTERS LEAVES PLANT PHYSIOLOGY, 4, 1994.
- INHIBITORS OF THE PROTON-SUCROSE SYMPORT ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS, 2, 1993.
- PROTON-COUPLED SUGAR AND AMINO-ACID TRANSPORTERS IN PLANTS ANNUAL REVIEW OF PLANT PHYSIOLOGY AND PLANT MOLECULAR BIOLOGY, 1993.
- CLONING A PLANT AMINO-ACID TRANSPORTER BY FUNCTIONAL COMPLEMENTATION OF A YEAST AMINO-ACID-TRANSPORT MUTANT PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 16, 1993.
- THE PROTON-SUCROSE SYMPORT PHOTOSYNTHESIS RESEARCH, 3, 1992.
- STRUCTURAL DETERMINANTS IN SUBSTRATE RECOGNITION BY PROTON AMINO-ACID SYMPORTS IN PLASMA-MEMBRANE VESICLES ISOLATED FROM SUGAR-BEET LEAVES ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS, 2, 1992.
- DELTA-PH-DEPENDENT AMINO-ACID-TRANSPORT INTO PLASMA-MEMBRANE VESICLES ISOLATED FROM SUGAR-BEET (BETA-VULGARIS L) LEAVES .2. EVIDENCE FOR MULTIPLE ALIPHATIC, NEUTRAL AMINO-ACID SYMPORTS PLANT PHYSIOLOGY, 4, 1991.
- DELTA-PH-DEPENDENT AMINO-ACID-TRANSPORT INTO PLASMA-MEMBRANE VESICLES ISOLATED FROM SUGAR-BEET LEAVES .1. EVIDENCE FOR CARRIER-MEDIATED, ELECTROGENIC FLUX THROUGH MULTIPLE TRANSPORT-SYSTEMS PLANT PHYSIOLOGY, 1, 1990.
- ELECTROGENICITY, PH-DEPENDENCE, AND STOICHIOMETRY OF THE PROTON-SUCROSE SYMPORT PLANT PHYSIOLOGY, 4, 1990.
- PROTON-COUPLED SUCROSE TRANSPORT IN PLASMALEMMA VESICLES ISOLATED FROM SUGAR-BEET (BETA-VULGARIS L CV GREAT WESTERN) LEAVES PLANT PHYSIOLOGY, 4, 1989.
- AMINO-ACID TRANSPORT INTO MEMBRANE-VESICLES ISOLATED FROM ZUCCHINI - EVIDENCE OF A PROTON-AMINO ACID SYMPORT IN THE PLASMALEMMA PLANT PHYSIOLOGY, 2, 1988.
- OATS TOLERANT OF PSEUDOMONAS-SYRINGAE PV TABACI CONTAIN TABTOXININE-BETA-LACTAM-INSENSITIVE LEAF GLUTAMINE SYNTHETASES PLANT PHYSIOLOGY, 2, 1988.
- TABTOXININE-BETA-LACTAM TRANSPORT INTO CULTURED CORN CELLS - UPTAKE VIA AN AMINO-ACID TRANSPORT-SYSTEM PLANT PHYSIOLOGY, 3, 1987.
- INVIVO INACTIVATION OF GLUTAMINE-SYNTHETASE BY TABTOXININE-BETA-LACTAM IN ZEA-MAYS SUSPENSION-CULTURE CELLS PHYSIOLOGICAL AND MOLECULAR PLANT PATHOLOGY, 2, 1987.
- POTASSIUM-TRANSPORT IN SUSPENSION-CULTURE CELLS AND PROTOPLASTS OF CARROT PLANT PHYSIOLOGY, 4, 1986.
- CALCIUM-TRANSPORT IN TONOPLAST AND ENDOPLASMIC-RETICULUM VESICLES ISOLATED FROM CULTURED CARROT CELLS PLANT PHYSIOLOGY, 2, 1986.