Plants acquire iron from soil by two specific mechanisms: i) reduction of Fe3+ to Fe2+, a reaction catalyzed by a transmembrane reductase activity, followed by Fe2+ uptake; ii) release of Fe3+-chelating compounds -phytosiderophores- which are taken up by roots in the ferrated form. The first mechanism is typical for dicots, while the second is used by gramineous species. Both mechanisms are induced by iron starvation. ys1 and ys3 maize mutants display an iron chlorosis in field or in hydroponic culture in the presence of ferric chelates (Fe-EDTA), but both mutants turn green if supplied with Fe2+. Greening takes also place when the mutants are grown in a culture tube together with wt plants in a solution with Fe-EDTA. For ys1 (but not for ys3), even cultivation in an exhausted nutrient solution in which a wt plant had been previously grown induces greening. wt plants produce a diffusible factor restoring iron uptake capability in the mutants; in the case of ys1, this factor is likely to be the phytosiderophore. Iron starvation induces in roots of wt an increase of in vito Fe3+-reductase activity as well as changes in the microsomal protein pattern; both mutants behave as starved wt even when grown in the presence of Fe3+-EDTA. Ferric-chelate-reductase zymograms of root microsoinal proteins electrofocused on polyacrylamide gels reveal the presence of several isozymes one of which, with an apparent pi of 6.4, is predominant in plasma membrane enriched fractions. In segregating progenies from Ys1/ys1 and Ys3/ys3 plants, normal and mutant seedlings show a similar IEF pattern; however the pi 6.4 isozyme present in the Ys1 background is missing in Ys3 and it is replaced by an isozyme with a pI of about 7.3. It could be that the two isoforms represent alleles of a gene encoding the ferric-reductase.
The yellow stripe 1 and 3 of maize: nutritional and biochemical studies
BRACALE, MARCELLA;
1994-01-01
Abstract
Plants acquire iron from soil by two specific mechanisms: i) reduction of Fe3+ to Fe2+, a reaction catalyzed by a transmembrane reductase activity, followed by Fe2+ uptake; ii) release of Fe3+-chelating compounds -phytosiderophores- which are taken up by roots in the ferrated form. The first mechanism is typical for dicots, while the second is used by gramineous species. Both mechanisms are induced by iron starvation. ys1 and ys3 maize mutants display an iron chlorosis in field or in hydroponic culture in the presence of ferric chelates (Fe-EDTA), but both mutants turn green if supplied with Fe2+. Greening takes also place when the mutants are grown in a culture tube together with wt plants in a solution with Fe-EDTA. For ys1 (but not for ys3), even cultivation in an exhausted nutrient solution in which a wt plant had been previously grown induces greening. wt plants produce a diffusible factor restoring iron uptake capability in the mutants; in the case of ys1, this factor is likely to be the phytosiderophore. Iron starvation induces in roots of wt an increase of in vito Fe3+-reductase activity as well as changes in the microsomal protein pattern; both mutants behave as starved wt even when grown in the presence of Fe3+-EDTA. Ferric-chelate-reductase zymograms of root microsoinal proteins electrofocused on polyacrylamide gels reveal the presence of several isozymes one of which, with an apparent pi of 6.4, is predominant in plasma membrane enriched fractions. In segregating progenies from Ys1/ys1 and Ys3/ys3 plants, normal and mutant seedlings show a similar IEF pattern; however the pi 6.4 isozyme present in the Ys1 background is missing in Ys3 and it is replaced by an isozyme with a pI of about 7.3. It could be that the two isoforms represent alleles of a gene encoding the ferric-reductase.
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