Hormones induce an Fe-deficiency-like root epidermal cell pattern in the Fe-inefficient tomato mutantfer

Abstract

The tomato mutantfer (Lycopersion esculentum L. T3238fer) displayed a chlorotic phenotype at normal external Fe levels. Root cells of the mutant are incompetent to take up iron in adequate amounts and are incapable to induce any of the known responses to Fe deficiency stress. We report here that the ethylene precursor 1-aminocyclopropane-l-carboxylic acid and the auxin analog 2,4-dichlorophenoxyacetic acid induce the formation of extra root hairs and transfer cells in the epidermis, thus mimicking the root-morphological Fe stress responses. In contrast, the physiological reactions involved in iron acquisition are not affected by the hormone treatment. These results indicate that ethylene is essential for transducing environmental signals into adaptive changes in root morphology. The data further suggest that the mutation does not affect necessary steps in the differentiation processes of epidermal cells. TheFER gene appears to control sensing of iron levels and/or the regulation of mechanisms involved in iron uptake.