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Direct Measurement of 59Fe-Labeled Fe2+ Influx in Roots of Pea Using a Chelator Buffer System to Control Free Fe2+ in
T. C. Fox1, J. E. Shaff, M. A. Grusak
1United 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.).
Plant Physiology
|May 1, 1996
Summary
Quantifying iron (Fe2+) transport in plants was challenging. This study developed new methods to accurately measure Fe2+ uptake in pea roots, revealing how iron deficiency and a specific mutant affect iron absorption.
Area of Science:
- Plant Physiology
- Biochemistry
- Molecular Biology
Background:
- Quantifying Fe2+ transport in plants is difficult due to challenges in controlling Fe2+ activity in aerated solutions and non-specific Fe binding to cell walls.
- Accurate measurement of Fe2+ influx is crucial for understanding plant iron nutrition and developing strategies to improve crop yields.
Purpose of the Study:
- To develop and apply novel methodologies for precisely quantifying unidirectional Fe2+ influx in plant roots.
- To investigate the influence of iron deficiency and a specific genetic mutation (brz) on Fe2+ uptake and translocation in pea (Pisum sativum).
Main Methods:
- Utilized a Fe(II)-3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine-4[prime]4"-disulfonic acid buffer system to control free Fe2+ activity in uptake solutions.
- Developed desorption methodologies to remove non-specifically bound Fe from the root apoplasm.
- Employed radiotracer (59Fe) uptake assays in pea roots and its 'brz' mutant to quantify Fe2+ influx, with low-temperature inhibition confirming true influx.
Main Results:
- Fe2+ influx into pea roots was significantly inhibited by low temperatures, confirming measurements reflected true plasma membrane transport.
- Fe deficiency stimulated both Fe2+ influx and translocation to the shoots in 'Sparkle' pea plants.
- The 'brz' mutant, exhibiting high ferric reductase activity, showed higher Fe2+ influx rates compared to iron-sufficient 'Sparkle' plants.
Conclusions:
- The study successfully quantified Fe2+ influx in plant roots using advanced buffer and desorption techniques.
- Results suggest that iron deficiency may induce Fe2+ transporter expression or enhance transporter activity.
- Enhanced ferric reductase activity in the 'brz' mutant appears to stimulate Fe2+ transport, highlighting the interplay between reduction and uptake mechanisms.