Dipartimento di Biologia, Istituto di Biofisica del CNR (IBF) - Sezione di Milano, Università degli Studi di Milano, Via Celoria 26, 20133 Milano, Italy.
Physiol Plant. 2011 Jun;142(2):144-56. doi: 10.1111/j.1399-3054.2011.01455.x. Epub 2011 Mar 9.
The phytotoxin fusicoccin (FC) was found to induce an increase in apoplastic H₂O₂ content in Arabidopsis thaliana cells, apparently linked to the presence of an as yet unidentified catalase inhibitor detectable even in the external medium of FC-treated cells. This study, aimed to further characterize the inhibitor's features, shows that (1) FC-induced H₂O₂ accumulation increases as a function of FC concentration and correlates to the amount of inhibitor released at apoplastic level. The pattern of H+ efflux, conversely, does not fit with that of these two parameters, suggesting that neither the production nor the release of the catalase inhibitor is linked to the main role of FC in activating the plasma membrane (PM) H+-ATPase; (2) treatment with 10 µM erythrosine B (EB) early and totally inhibits net H+ and K+ fluxes across the PM, indicative of the H+ pump activity; nevertheless, also in these conditions a huge FC-induced H₂O₂ accumulation occurs, confirming that this effect is not related to the FC-induced PM H+-ATPase activation; (3) the inhibitor's release increases with time in all conditions tested and is markedly affected by extracellular pH (a higher pH value being associated to a larger efflux), in agreement with a weak acid release; and (4) the inhibitor can be almost completely recovered in a CH₂C₂-soluble fraction extracted from the incubation medium by sequential acid-base partitioning which contains nearly all of the organic acids released. These final results strongly suggest that the metabolite responsible for the FC-induced catalase inhibition belongs to the organic acid class.
植物毒素 fusicoccin (FC) 被发现能诱导拟南芥细胞中外质 H₂O₂ 含量增加，显然与一种尚未鉴定的过氧化氢酶抑制剂的存在有关，这种抑制剂甚至在 FC 处理细胞的外质中也能检测到。本研究旨在进一步表征该抑制剂的特征，结果表明：（1）FC 诱导的 H₂O₂ 积累随 FC 浓度的增加而增加，与在质外体水平释放的抑制剂量相关。相反，H+外排的模式与这两个参数不匹配，表明该抑制剂的产生和释放都与 FC 激活质膜 (PM) H+-ATPase 的主要作用无关；（2）用 10 µM 血根碱 B (EB) 早期和完全抑制 PM 上的净 H+和 K+跨膜通量，表明 H+泵的活性；然而，即使在这些条件下，也会发生巨大的 FC 诱导的 H₂O₂ 积累，证实这一效应与 FC 诱导的 PM H+-ATPase 激活无关；（3）在所有测试的条件下，抑制剂的释放随时间增加，并且受细胞外 pH 的显著影响（较高的 pH 值与较大的外排相关），与弱酸性释放一致；（4）抑制剂可以通过顺序酸碱分配从孵育介质中用 CH₂C₂ 可溶部分几乎完全回收，该部分含有几乎所有释放的有机酸。这些最终结果强烈表明，导致 FC 诱导的过氧化氢酶抑制的代谢物属于有机酸类。
