Fernandez-Pascual Mercedes, Lucas M Mercedes, de Felipe Maria Rosario, Boscá Lisardo, Hirt Heribert, Golvano Maria Pilar
Instituto de Recursos Naturales, Centro de Ciencias Medioambientales, Consejo Superior de Investigaciones Científicas, Serrano, 115 dpdo, E-28006 Madrid, Spain.
J Exp Bot. 2006;57(11):2735-42. doi: 10.1093/jxb/erl038. Epub 2006 Jul 25.
In plants, mitogen-activated protein kinases (MAPKs) are involved in signalling to hormones, cell cycle regulation, stresses, and plant defence responses. In this work, several MAPKs were detected by immunobloting in roots and nodules of Lupinus albus produced by inoculation with Bradyrhizobium sp. (Lupinus). In vitro kinase assays showed that inoculation of seedling roots with B. sp. (Lupinus) activates salt stress-inducible and stress-activated MAPKs after 5 min of incubation. By contrast, inoculation with dead B. sp. (Lupinus) or the heterologous bacteria Sinorhizobium meliloti did not induce salt stress-inducible and stress-activated MAPK activities. In vivo experiments showed that inoculation with B. sp. (Lupinus) induced the activation of MAPKs in roots. The maximal activation was in the region of the root tip with emerging hairs, which corresponds to the infection zone. The p38 MAPK inhibitors SB 202190 and SB 203580 blocked these kinase activities. Experiments with SB 202190 and the MAPKK inhibitor UO 126 altered the pattern of nodulation in the main root, decreasing the number and weight of nodules produced in the upper sites while increasing the nodule number in the younger lower root zone. These data suggest that MAPK inhibition blocks early events in the susceptible root zone to rhizobial infection, delaying nodulation, and support a role for MAPKs in the infection and nodulation of L. albus by B. sp. (Lupinus).
在植物中，丝裂原活化蛋白激酶（MAPKs）参与激素信号传导、细胞周期调控、应激反应及植物防御反应。在本研究中，通过免疫印迹法在接种慢生根瘤菌（羽扇豆）后产生的白羽扇豆的根和根瘤中检测到了几种MAPKs。体外激酶分析表明，用慢生根瘤菌（羽扇豆）接种幼苗根5分钟后可激活盐胁迫诱导型和胁迫激活型MAPKs。相比之下，接种死的慢生根瘤菌（羽扇豆）或异源细菌苜蓿中华根瘤菌不会诱导盐胁迫诱导型和胁迫激活型MAPK活性。体内实验表明，接种慢生根瘤菌（羽扇豆）可诱导根中MAPKs的激活。最大激活发生在有新毛出现的根尖区域，该区域对应于感染区。p38 MAPK抑制剂SB 202190和SB 203580可阻断这些激酶活性。用SB 202190和MAPKK抑制剂UO 126进行的实验改变了主根中的结瘤模式，减少了上部位点产生的根瘤数量和重量，同时增加了较年轻的下部根区的根瘤数量。这些数据表明，MAPK抑制可阻断易感根区对根瘤菌感染的早期事件，延迟结瘤，并支持MAPKs在慢生根瘤菌（羽扇豆）对白羽扇豆的感染和结瘤过程中发挥作用。
