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Uptake kinetics of iron‐phytosiderophores in two maize genotypes differing in iron efficiency
Author(s) -
Wirén Nicolaus,
Marschner Horst,
Römheld Volker
Publication year - 1995
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1995.tb05107.x
Subject(s) - kinetics , mutant , zea mays , chemistry , chelation , dry weight , enzyme kinetics , biochemistry , biophysics , biology , botany , enzyme , gene , agronomy , inorganic chemistry , physics , quantum mechanics , active site
Iron inefficiency in the maize ( Zea mays L.) mutant ysl is caused by a defect in the uptake system for Fe‐phytosiderophores. To characterize this defect further, the uptake kinetics of Fe‐phytosiderophores in ysl was compared to the Fe‐efficient maize cultivar Alice. Short‐term uptake of 59 Fe‐labeled Fe‐deoxymugineic acid (Fe‐DMA) was measured over a concentration range of 0.03 to 300 μM. Iron uptake in Fe‐deficient plants followed Michaelis‐Menten kinetics up to about 30 μM and was linear at higher concentrations, indicating two kinetically distinct components in the uptake of Fe‐phytosiderophores. The saturable component had similar K m (∼ 10 μM) in both genotypes. In contrast. V max was 5.5 μmol Fe‐DMA g −1 dry weight [30 min] −1 in Alice, but only 0.6 μmol Fe‐DMA g −1 dry weight [30 min] −1 in ysl . Uptake experiments with double‐labeled 59 Fe‐[ 14 C]DMA suggest that in both cultivars Fe‐DMA was taken up by the roots as the intact chelate. The results indicate the existence of a high‐affinity and a low‐affinity uptake system mediating Fe‐phytosiderophore transport across the root plasma membrane in maize. Apparently, the mutation responsible for Fe inefficiency in ysl affected high‐affected uptake and led to a decrease in activity and/or number of Fe‐phytosiderophore transporters.