Iwate Biotechnology Research Center, Narita 22-174-4, Kitakami, Iwate 024-0003, Japan.
Mol Plant Pathol. 2003 Sep 1;4(5):383-91. doi: 10.1046/j.1364-3703.2003.00186.x.
SUMMARY Mitogen-activated protein kinases (MAPKs) play pivotal roles in the signal transduction pathway of plant defence responses against pathogens. A search for MAPK-interacting proteins revealed an interaction between a Nicotiana benthamiana MAPK, SIPK (NbSIPK) and cytosolic Hsp90 (NbHsp90c-1) in yeast two-hybrid assay. To study the function of Hsp90 in disease resistance, we silenced NbHsp90c-1 in N. benthamiana by virus-induced gene silencing (VIGS) with Potato virus X (PVX). NbHsp90c-1 silenced plants exhibited: (1) a stunted phenotype, (2) no hypersensitive response (HR) development after infiltration with the Phytophthora infestans protein INF1 and a non-host pathogen Pseudomonas cichorii that normally triggers HR in N. benthamiana, (3) compromised non-host resistance to P. cichorii, and (4) consistently reduced transcription levels of PR (pathogenesis related) protein genes. Similar phenotypes were observed also for plants in which a cytosolic Hsp70 (NbHsp70c-1), a gene for another class of molecular chaperon, was silenced. Hsp90 was isolated as a MAPK-interacting protein in yeast two-hybrid assay, therefore we tested the effect of NbHsp90c-1 silencing as well as NbHsp70c-1 silencing on the HR development caused by infiltration of a hyperactive potato MAPKK (StMEK1(DD)). No difference in the timing or extent of HR was found among NbHsp90c-1 silenced, NbHsp70c-1 silenced and control plants. This result indicates that observed impairment of INF1- and P. cichorii-mediated HR development in NbHsp90c-1 silenced and NbHsp70c-1 silenced plants was not caused by the abrogation in MAPK function downstream of active MAPKK that leads to HR. These findings suggest essential roles of Hsp90 and Hsp70 in plant defence signal transduction pathway upstream or independent of the MAPK cascade.
摘要 丝裂原活化蛋白激酶（MAPKs）在植物对病原体防御反应的信号转导途径中发挥关键作用。在寻找 MAPK 相互作用蛋白的过程中，在酵母双杂交实验中发现了拟南芥 MAPK、SIPK（NbSIPK）和细胞质 Hsp90（NbHsp90c-1）之间的相互作用。为了研究 Hsp90 在抗病性中的功能，我们通过病毒诱导的基因沉默（VIGS）用马铃薯病毒 X（PVX）沉默了 N. benthamiana 中的 NbHsp90c-1。NbHsp90c-1 沉默的植物表现出：（1）矮小的表型，（2）在渗透用 Phytophthora infestans 蛋白 INF1 和非宿主病原体 Pseudomonas cichorii 后不发育过敏反应（HR），而正常情况下，HR 会在 N. benthamiana 中触发，（3）非宿主对 P. cichorii 的抗性受损，（4）PR（发病相关）蛋白基因的转录水平一致降低。在用另一种分子伴侣类的细胞质 Hsp70（NbHsp70c-1）沉默基因的植物中也观察到类似的表型。Hsp90 在酵母双杂交实验中被鉴定为 MAPK 相互作用蛋白，因此我们测试了 NbHsp90c-1 沉默以及 NbHsp70c-1 沉默对渗透超活性马铃薯 MAPKK（StMEK1（DD））引起的 HR 发展的影响。在 NbHsp90c-1 沉默、NbHsp70c-1 沉默和对照植物之间，没有发现 HR 发展的时间或程度有差异。这一结果表明，在 NbHsp90c-1 沉默和 NbHsp70c-1 沉默植物中，观察到的 INF1 和 P. cichorii 介导的 HR 发展受损不是由于导致 HR 的活性 MAPKK 下游的 MAPK 功能丧失所致。这些发现表明 Hsp90 和 Hsp70 在植物防御信号转导途径中发挥重要作用，该途径位于 MAPK 级联的上游或独立于 MAPK 级联。
