Dell'Orto M, Santi S, De Nisi P, Cesco S, Varanini Z, Zocchi G, Pinton R
Dipartimento di Produzione Vegetale, University of Milan, Italy.
J Exp Bot. 2000 Apr;51(345):695-701.
One of the mechanisms through which some strategy I plants respond to Fe-deficiency is an enhanced acidification of the rhizosphere due to proton extrusion. It was previously demonstrated that under Fe-deficiency, a strong increase in the H(+)-ATPase activity of plasma membrane (PM) vesicles isolated from cucumber roots occurred. This result was confirmed in the present work and supported by measurement of ATP-dependent proton pumping in inside-out plasma membrane vesicles. There was also an attempt to clarify the regulatory mechanism(s) which lead to the activation of the H(+)-ATPase under Fe-deficiency conditions. Plasma membrane proteins from Fe-deficient roots submitted to immunoblotting using polyclonal antibodies showed an increased level in the 100 kDa polypeptide. When the plasma membrane proteins were treated with trypsin a 90 kDa band appeared. This effect was accompanied by an increase in the enzyme activity, both in the Fe-deficient and in the Fe-sufficient extracts. These results suggest that the increase in the plasma membrane H(+)-ATPase activity seen under Fe-deficiency is due, at least in part, to an increased steady-state level of the 100 kDa polypeptide.
一些策略I植物对缺铁作出反应的机制之一是由于质子外排导致根际酸化增强。先前已证明,在缺铁条件下,从黄瓜根部分离的质膜(PM)囊泡的H(+)-ATPase活性大幅增加。本研究证实了这一结果,并通过对内外翻转质膜囊泡中ATP依赖性质子泵的测量得到支持。同时也尝试阐明在缺铁条件下导致H(+)-ATPase激活的调控机制。使用多克隆抗体对缺铁根的质膜蛋白进行免疫印迹分析,结果显示100 kDa多肽的水平增加。当质膜蛋白用胰蛋白酶处理时,出现了一条90 kDa的条带。在缺铁和铁充足的提取物中,这种效应都伴随着酶活性的增加。这些结果表明,缺铁条件下质膜H(+)-ATPase活性的增加至少部分归因于100 kDa多肽稳态水平的提高。