Crowley D E, Reid C P, Szaniszlo P J
Department of Forestry, IFAS, University of Florida, Gainesville, Florida 32611.
Plant Physiol. 1988 Jul;87(3):680-5. doi: 10.1104/pp.87.3.680.
Iron uptake by oat (Avena sativa cv Victory) was examined under hydroponic chemical conditions that required direct utilization of microbial siderophores for iron transport. Measurements of iron uptake rates by excised roots from the hydroxamate siderophores, ferrichrome, ferrichrome A, coprogen, ferrioxamine B (FOB), and rhodotorulic acid (RA) showed all five of the siderophores supplied iron, but that FOB and RA were preferentially utilized. FOB-mediated iron uptake increased four-fold when roots were preconditioned to iron stress and involved an active, iron-stress induced transport system that was inhibited by 5 millimolar sodium azide or 0.5 millimolar dinitrophenol. Kinetic studies indicated partial saturation with an apparent K(m) of 5 micromolar when FOB was supplied at 0.1 to 50 micromolar concentrations. Whole plant experiments confirmed that 5 micromolar FOB was sufficient for plant growth. Siderophore-mediated iron transport was inhibited by Cr-ferrichrome, an analog of ferrated siderophore. Our results confirm the existence of a microbial siderophore iron transport system in oat which functions within the physiological concentrations produced and used by soil microorganisms.
在水培化学条件下研究了燕麦（燕麦品种Victory）对铁的吸收情况，该条件要求直接利用微生物铁载体进行铁运输。对来自异羟肟酸铁载体、高铁色素、高铁色素A、粪生绿素、铁胺B（FOB）和蔷薇霉素（RA）的离体根的铁吸收速率测量表明，所提供的所有五种铁载体都能提供铁，但FOB和RA被优先利用。当根预先适应铁胁迫时，FOB介导的铁吸收增加了四倍，并且涉及一个活跃的、铁胁迫诱导的运输系统，该系统被5毫摩尔叠氮化钠或0.5毫摩尔二硝基苯酚抑制。动力学研究表明，当以0.1至50微摩尔浓度提供FOB时，其表现出部分饱和，表观K（m）为5微摩尔。整株植物实验证实，5微摩尔FOB足以满足植物生长。铁载体介导的铁运输受到铁化铁载体类似物铬-高铁色素的抑制。我们的结果证实了燕麦中存在一种微生物铁载体铁运输系统，该系统在土壤微生物产生和使用的生理浓度范围内发挥作用。
