Michael A. Grusak, Ph.D.
Professor of Pediatrics, Baylor College of Medicine
Plant Physiologist, Agricultural Research Service
Understanding Plant Nutrient Transport to Improve Food Crop Nutritional Quality and Assess Phytonutrient Bioavailability
I am involved in both plant physiology and human nutrition studies. The plant physiology research concerns the long-distance translocation of organic and inorganic nutrients within the phloem and/or xylem system of plants, as well as the short-distance transport of mineral ions across various cellular and organellar membranes. Of major interest is whole-plant micronutrient nutrition (primarily iron and zinc) and the interrelationship of shoot and root factors that homeostatically regulate root micronutrient acquisition and the eventual deposition of micronutrient metals in edible plant parts (e.g., seeds). The long-term goals are to characterize the dynamics of nutrient flow within plants to determine the biophysical/molecular signals that regulate source-to-sink nutrient partitioning and to use these data to develop strategies for enhancing the nutritional quality of plant foods. Methodologies utilized include stable-isotope labeling and whole-plant partitioning analysis, membrane flux analysis using radioisotopes and/or electrophysiology, and molecular techniques to identify and characterize genes and gene products relevant to metal transport and metal homeostasis.
The human nutrition research involves the development of hydroponic and gaseous plant labeling equipment to generate stable isotopically labeled plant foods and bioproducts for human consumption. The labeled foods are used to address questions about the absorption and utilization of specific nutrients. The current emphasis of this research is on the bioavailability of iron, zinc, and amino acids from seed sources, or calcium, selenium, carotenoids, and phylloquinone (vitamin K) from various vegetable sources.
Waters BM, Uauy C, Dubcovsky J, Grusak MA. Wheat (Triticum aestivum) NAM proteins regulate the translocation of iron, zinc, and nitrogen compounds from vegetative tissues to grain. J Exp Bot 60:4263-4274, 2009.
Sperotto RA, Ricachenevsky FK, Duarte GL, Boff T, Lopes KL, Sperb ER, Grusak MA, Fett JP. Identification of up-regulated genes in flag leaves during rice grain filling and characterization of OsNAC5, a new ABA-dependent transcription factor. Planta 230:985-1002, 2009.
Klein MA, Grusak MA. Identification of nutrient and physical seed trait QTLs in the model legume, Lotus japonicus. Genome 52:677-691, 2009.
Sankaran RP, Huguet T, Grusak MA. Identification of QTL affecting seed mineral concentrations and content in the model legume Medicago truncatula. Theor Appl Gen 119:241-253, 2009.
Fu X, Peterson JW, Hdeib M, Booth SL, Grusak MA, Lichtenstein AH, Dolnikowski GG. Measurement of deuterium-labeled phylloquinone in plasma by high-performance liquid chromatography/mass spectrometry. Anal Chem 81:5421-5425, 2009.
Tang G, Qin J, Dolnikowski GG. Russell RM, Grusak MA. Golden Rice is an effective source of vitamin A. Am J Clin Nutr 89:1776-1783, 2009.
Blair MW, Astudillo C, Grusak MA, Graham R, Beebe SE. Inheritance of seed iron and zinc concentrations in common bean (Phaseolus vulgaris L.). Mol Breeding 23:197-207, 2009.
Grusak MA. Nutritional and health-beneficial quality. In: Erskine W, Muehlbauer F, Sarker A, Sharma B, eds., The Lentil: Botany, Production, and Uses, CABI, pp. 368-390, 2009.
Vasconcelos MW, Li GW, Lubkowitz MA, Grusak MA. Characterization of the PT clade of oligopeptide transporters in rice. Plant Genome 1:77-88, 2008.
Waters BL, Grusak MA. Quantitative trait locus mapping for seed mineral concentrations in two Arabidopsis thaliana recombinant inbred populations. New Phytol 179:1033-1047, 2008.
Grusak MA. Genetic diversity for seed mineral composition in the wild legume Teramnus labialis. Plant Foods Human Nutr 63:105-109, 2008.
Wang J, Wang Y, Wang Z, Li L, Qin J, Lai W, Fu Y, Suter PM, Russell RM, Grusak MA, Tang G, Yin S. Vitamin A equivalence of spirulina β-carotene in Chinese adults as assessed by using a stable-isotope reference method. Am J Clin Nutr 87:1730-1737, 2008.
Waters BL, Grusak MA. Whole-plant mineral partitioning throughout the life cycle in Arabidopsis thaliana ecotypes Columbia, Landsberg erecta, Cape Verde Islands, and the mutant line ysl1ysl3. New Phytol 177:389-405, 2008.
O'Rourke JA, Charlson DV, Gonzalez DO, Vodkin LO, Graham MA, Cianzio SR, Grusak MA, Shoemaker RC. Microarray analysis of iron deficiency chlorosis in near-isogenic soybean lines. Biomed Central (BMC) Genomics 8:476, 2007.
Farnham MW, Hale AJ, Grusak MA, Finley JW. Genotypic and environmental effects on selenium concentration of broccoli heads grown without supplemental selenium fertilizer. Plant Breeding 126:195-200, 2007.
Vasconcelos M, Eckert H, Arahana V, Graef G, Grusak MA, Clemente T. Molecular and phenotypic characterization of transgenic soybean expressing the Arabidopsis ferric chelate reductase gene, FRO2. Planta 224:1116-1128, 2006.
Grusak MA. Golden Rice gets a boost from maize. Nat Biotechnol 23:429-30, 2005. Wang HL, Grusak MA. Structure and development of Medicago truncatula pod wall and seed coat. Ann Bot 95:737-747, 2005.
Pomper KW, Grusak MA . Calcium uptake and whole-plant water use influence pod calcium concentration in snap bean plants. J Amer Soc Hort Sci 129:890-895, 2004.
Grusak MA, Rogers RB, Yousef G, Erdman Jr JW, Lila MA. An enclosed-chamber labeling system for the safe 14C-enrichment of phytochemicals in plant cell suspension cultures. In vitro Cell Develop Biol-Plant 40:80-85, 2004.
Lopéz-Millán AF, Ellis DR, Grusak MA. Identification and characterization of several new members of the ZIP family of metal ion transporters in Medicago truncatula. Plant Mol Biol 54:583-596, 2004.
Erkkila AT, Lichtenstein AH, Dolnikowski GG, Grusak MA, Jalbert SM, Aquino KA, Peterson JW, Booth SL. Plasma transport of vitamin K in men using deuterium-labeled collard greens. Metabolism 53:215-221, 2004. Wang TL,
Domoney C, Hedley CL, Casey R, Grusak MA. Can we improve the nutritional quality of legume seeds? Plant Physiol 131:886-891, 2003.
Grusak MA. Phytochemicals in plants: genomics-assisted plant improvement for nutritional and health benefits. Curr Opinion Biotechnol 13:508-511, 2002.
Grusak MA, DellaPenna D. Improving the nutrient composition of plants to enhance human nutrition and health. Annu Rev Plant Physiol Plant Mol Biol 50:133-161, 1999.