Kamoun S, van West P, de Jong A J, de Groot K E, Vleeshouwers V G, Govers F
Department of Phytopathology, Wageningen Agricultural University, The Netherlands.
Mol Plant Microbe Interact. 1997 Jan;10(1):13-20. doi: 10.1094/MPMI.1997.10.1.13.
Most species of the genus Phytophthora produce 10-kDa extracellular protein elicitors, collectively termed elicitins. Elicitins induce hypersensitive response in a restricted number of plants, particularly in the genus Nicotiana within the Solanaceae family. A cDNA encoding INF1, the major secreted elicitin of Phytophthora infestans, a pathogen of solanaceous plants, was isolated and characterized. The expression of the corresponding inf1 gene during the disease cycle of P. infestans was analyzed. inf1 was shown to be expressed in mycelium grown in various culture media, whereas it was not expressed in sporangiospores, zoospores, cysts, and germinating cysts. In planta, during infection of potato, particularly during the biotrophic stage, expression of inf1 was down-regulated compared to in vitro. The highest levels of expression of inf1 were observed in in vitro grown mycelium and in late stages of infection when profuse sporulation and leaf necrosis occur. The potential role of INF1 as an elicitor in interactions between P. infestans and Solanum species was investigated. Nineteen lines, representing nine solanaceous species with various levels of resistance to P. infestans, were tested for response to an Escherichia coli expressed INF1. Within the genus Solanum, resistance to P. infestans did not appear to be mediated by a defense response elicited by INF1. However, INF1 recognition could be a component of nonhost resistance of tobacco to P. infestans.
疫霉属的大多数物种会产生10 kDa的细胞外蛋白激发子，统称为激发素。激发素能在有限数量的植物中诱导过敏反应，尤其是在茄科烟草属植物中。编码INF1（致病疫霉的主要分泌激发素，致病疫霉是茄科植物的一种病原体）的cDNA被分离并进行了表征。分析了致病疫霉在病害循环过程中相应inf1基因的表达情况。结果表明，inf1在多种培养基中生长的菌丝体中表达，而在游动孢子、游动孢子囊、包囊和萌发的包囊中不表达。在植物体内，在感染马铃薯的过程中，尤其是在活体营养阶段，与体外相比，inf1的表达下调。在体外生长的菌丝体以及感染后期大量产孢和叶片坏死时，观察到inf1的最高表达水平。研究了INF1作为激发素在致病疫霉与茄属物种相互作用中的潜在作用。测试了代表9种对致病疫霉具有不同抗性水平的茄科物种的19个品系对大肠杆菌表达的INF1的反应。在茄属植物中，对致病疫霉的抗性似乎不是由INF1引发的防御反应介导的。然而，INF1识别可能是烟草对致病疫霉非寄主抗性的一个组成部分。
