PLANT PHYSIOLOGY , Vol 111, Issue 1 93-100, Copyright © 1996 by American Society of Plant Biologists

WHOLE PLANT, ENVIRONMENTAL, AND STRESS PHYSIOLOGY

Direct Measurement of 59Fe-Labeled Fe2+ Influx in Roots of Pea Using a Chelator Buffer System to Control Free Fe2+ in Solution

T. C. Fox, J. E. Shaff, M. A. Grusak, W. A. Norvell, Y. Chen, R. L. Chaney and L. V. Kochian
United States Plant Soil and Nutrition Laboratory, United States Department of Agriculture-Agricultural Research Service (USDA-ARS), Cornell University, Ithaca, New York 14853 (T.C.F., J.E.S., W.A.N., L.V.K.)

Fe2+ transport in plants has been difficult to quantify because of the inability to control Fe2+ activity in aerated solutions and non-specific binding of Fe to cell walls. In this study, a Fe(II)-3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine-4[prime]4"-disulfonic acid buffer system was used to control free Fe2+ in uptake solutions. Additionally, desorption methodologies were developed to adequately remove nonspecifically bound Fe from the root apoplasm. This enabled us to quantify unidirectional Fe2+ influx via radiotracer (59Fe) uptake in roots of pea (Pisum sativum cv Sparkle) and its single gene mutant brz, an Fe hyperaccumulator. Fe influx into roots was dramatically inhibited by low temperature, indicating that the measured Fe accumulation in these roots was due to true influx across the plasma membrane rather than nonspecific binding to the root apoplasm. Both Fe2+ influx and Fe translocation to the shoots were stimulated by Fe deficiency in Sparkle. Additionally, brz, a mutant that constitutively exhibits high ferric reductase activity, exhibited higher Fe2+ influx rates than +Fe-grown Sparkle. These results suggest that either Fe deficiency triggers the induction of the Fe2+ transporter or that the enhanced ferric reductase activity somehow stimulates the activity of the existing Fe2+ transport protein.

This article has been cited by other articles:

				H. Wu, L. Li, J. Du, Y. Yuan, X. Cheng, and H.-Q. Ling Molecular and Biochemical Characterization of the Fe(III) Chelate Reductase Gene Family in Arabidopsis thaliana Plant Cell Physiol., September 1, 2005; 46(9): 1505 - 1514. [Abstract] [Full Text] [PDF]

				G. Vert, N. Grotz, F. Dedaldechamp, F. Gaymard, M. L. Guerinot, J.-F. Briat, and C. Curie IRT1, an Arabidopsis Transporter Essential for Iron Uptake from the Soil and for Plant Growth PLANT CELL, June 1, 2002; 14(6): 1223 - 1233. [Abstract] [Full Text] [PDF]

				S. Thomine, R. Wang, J. M. Ward, N. M. Crawford, and J. I. Schroeder Cadmium and iron transport by members of a plant metal transporter family in Arabidopsis with homology to Nramp genes PNAS, April 25, 2000; 97(9): 4991 - 4996. [Abstract] [Full Text] [PDF]

				W. Schmidt, J. Tittel, and A. Schikora Role of Hormones in the Induction of Iron Deficiency Responses in Arabidopsis Roots Plant Physiology, April 1, 2000; 122(4): 1109 - 1118. [Abstract] [Full Text]

				C. K. Cohen, T. C. Fox, D. F. Garvin, and L. V. Kochian The Role of Iron-Deficiency Stress Responses in Stimulating Heavy-Metal Transport in Plants Plant Physiology, March 1, 1998; 116(3): 1063 - 1072. [Abstract] [Full Text]