Characterization of iron uptake by iron-efficient and iron-inefficient soybeans in cell suspension culture

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Abstract
Cell suspension cultures of Fe‐efficient Hawkeye (HA) and Fe‐inefficient Pl‐54619–5–1 (PI) soybeans [Glycine max (L.) Merrill] respond differently to Fe‐stress and take up different quantities of Fe, but reflect differences observed at the whole plant level. Short‐term Fe uptake experiments showed that HA‐soybean cells respond to Fe‐stress by increasing their ability for Fe uptake. Pi‐soybean cells have a significantly decreased ability for Fe uptake when Fe‐stressed. Kinetic studies indicated that HA‐soybean cells had greater Km and Vmax values for Fe uptake than PI‐soybean cells. The data indicate that HA‐soybean cells have an inducible Fe transport system that is stimulated under conditions of Fe‐stress. It appears that when Fe‐stressed, HA‐soybean cells may increase the number of Fe reducing and/or Fe transporting sites, thus increasing their ability for Fe uptake. Iron is taken up as the reduced ferrous (Fe2+) form by a system showing a high specificity for Fel as indicated by competing cation studies. Dinitrophenol did not inhibit short‐term Fe uptake, while malonic acid decreased Fe uptake in both cell lines. This indicates that NADH may be involved in the Fe reduction and/or Fe transport process, perhaps as an electron source for ferric (Fe3+) iron reduction.

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