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ARS Home » Northeast Area » Ithaca, New York » Robert W. Holley Center for Agriculture & Health » Research » Publications at this Location » Publication #35662
Title: IRON REQUIREMENT FOR AND EFFECTS OF PROMOTERS AND INHIBITORS OF ETHYLENE ACTION ON STIMULATION OF FE(III)-CHELATE REDUCTASE IN ROOTS OF STRATEGY I SPECIES

Author
item ROMERA FRANCISCO - UNIV. CORDOBA, SPAIN
item Welch, Ross
item Norvell, Wendell
item Schaefer, Stephen

Submitted to: Biometals
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary: Globally, iron deficiency is the most prevalent nutrient deficiency among humans with over 2 billion people affected in both developing and developed nations. Iron deficiency is also prevalent in many agriculturally important crops in the United States and in other countries. However, the mechanisms controlling iron uptake and translocation in food crops are poorly understood. More basic information is required on these mechanisms before new food crops can be developed that accumulate more iron in their edible portions as well as crops that have the capacity to grow normally on soils with low iron availability status. Using mutant genotypes of pea and tomato, we established that over expression of iron-chelate root reductase activity was related to ethylene action. Possibly, these mutants are defective in their ability to regulate root-ethylene production. Additionally, we showed that the phytometallophore iron complex, iron (II)-nicotianamine, was not the repressor of the gene responsible for root-iron(III)-chelate reductase induction. The possibility remains that nicotianamine may affect iron(III)-chelate reductase activity by influencing ethylene biosynthesis. An improved understanding of the regulation of iron uptake will contribute to alleviation of iron deficiency in plants and, possibly, to increasing the iron content of the edible portions of food crops. This, in turn, could help to lower the incidence of iron deficiency in people.

Technical Abstract: Recently, ethylene was reported to be involved in the regulation of Fe(III)-chelate reducing capacity by cucumber (Cucumis sativus L.) roots (Romera and Alcantara, 1993, 1994). Here, we studied the effect of two ethylene inhibitors, AOA (aminooxyacetic acid) and cobalt (Co), on the Fe(III) reducing capacity in roots of mutant genotypes [E107 pea [Pisum sativum L. (brz, brz)] and chloronerva tomato (Lycopersicon esulentum L.] that exhibit high rates of Fe(III)-chelate reduction and excessive Fe accumulation. The ethylene inhibitors, AOA and Co, markedly inhibited Fe(III)-chelate reducing capcity in roots of both genotypes. Over- expression of root Fe(III) reductase activity by both mutants appears to be related to ethylene. Possibly, both mutants are genetically defective in their ability to regulate root-ethylene production. The large inhibitory effect of both ethylene inhibitors on Fe(III)-chelate reducing capacity in roots of the mutant tomato genotype, chloronerva, disputes the contention that the nicotianamine-Fe(II) complex is the repressor of the gene responsible for Fe(III)-chelate reductase activity, as previously suggested by others (Scholz et al., 1988). However, since nicotianamine shares the same biosynthetic precursor as ethylene, i.e. SAM (S-adenosyl methionine), nicotianamine may affect Fe(III)-chelate reductase activity in dicot and non-grass monocot roots by influencing ethylene biosynthesis.