Characterization of mugineic-acid-Fe transporter in Fe-deficient barley roots using the multi-compartment transport box method

Summary We have investigated the mugineicacid-Fe transport activity of Fe-deficient barley roots, using the multi-compartment transport box system. The roots maintained Fe transport activity for 20 h after excision. The following results were obtained. (1) In Fe-deficient roots, mugineic acid addition enhanced the transport of Fe by 32.2 times over that of the control (with FeC1₃ addition). (2) The mugineic-acid-⁵⁵Fe transport activity of Fe-deficient roots was 18.4-fold higher than that of the Fe-sufficient roots. (3) The mugineic-acid-⁵⁵Fe transport activity was decreased (7.13% based on the control) by treatment with 5 M carbonylcyanidem-chlorophenyl hydrazone (CCCP). Pretreatment with 0.1 mM dicyclohexyl carbodiimide (DCCD) lowered the transport activity (10.7% based on the control) and 1 mMN-ethylmaleimide (NEM) pretreatment reduced the transport activity to a value equivalent to 2.41% of that in the control. It is concluded that mugineicacid-Fe transporter is induced in its activity and/or amount by Fe-deficiency treatment and has an SH residue at its active site, and that the transporter needs the proton motive force produced by ATPase. We detected three polypeptides (14, 28 and 40 kDa) in the root plasma membrane that were induced under Fe-deficiency treatment.Abbreviations p-APMSF (p-amidinophenyl)methanesulfonyl fluoride hydrochloride - CCCP carbonylcyanide m-chlorophenylhydrazone - DCCD dicyclohexylcabodiimide - DMSO dimethyl sulfoxide - MA mugineic acid - NEM N-ethylmaleimide