Galiana E, Bonnet P, Conrod S, Keller H, Panabières F, Ponchet M, Poupet A, Ricci P
Station de Botanique et de Pathologie Végétale, Institute National de la Recherche Agronomique, Antibes, France.
Plant Physiol. 1997 Dec;115(4):1557-67. doi: 10.1104/pp.115.4.1557.
The hypersensitive response and systemic acquired resistance (SAR) can be induced in tobacco (Nicotiana tabacum L.) plants by cryptogein, an elicitin secreted by Phytophthora cryptogea. Stem application of cryptogein leads to the establishment of acquired resistance to subsequent leaf infection with Phytophthora parasitica var nicotianae, the agent of the tobacco black shank disease. We have studied early events that occur after the infection and show here that a tobacco gene encoding the extracellular S-like RNase NE is expressed in response to inoculation with the pathogenic fungus. Upon induction of SAR with cryptogein, the accumulation of NE transcripts coincided with a rapid induction of RNase activity and with the increase in the activity of at least two different extracellular RNases. Moreover, exogenous application of RNase activity in the extracellular space of leaves led to a reduction of the fungus development by up to 90%, independently of any cryptogein treatment and in the absence of apparent necrosis. These results indicate that the up-regulation of apoplastic RNase activity after inoculation could contribute to the control of fungal invasion in plants induced to SAR with cryptogein.
隐地蛋白（一种由隐地疫霉分泌的激发子）可诱导烟草（Nicotiana tabacum L.）植株产生过敏反应和系统获得性抗性（SAR）。在烟草茎部施用隐地蛋白可使其对烟草黑胫病病原菌烟草寄生疫霉随后的叶片感染建立起获得性抗性。我们研究了感染后早期发生的事件，并在此表明，一个编码细胞外S类核糖核酸酶NE的烟草基因在接种致病真菌后表达。在用隐地蛋白诱导SAR时，NE转录本的积累与核糖核酸酶活性的快速诱导以及至少两种不同细胞外核糖核酸酶活性的增加同时发生。此外，在叶片的细胞外空间外源施加核糖核酸酶活性可使真菌生长减少多达90%，这与任何隐地蛋白处理无关且不存在明显坏死现象。这些结果表明，接种后质外体核糖核酸酶活性的上调可能有助于控制用隐地蛋白诱导产生SAR的植物中的真菌入侵。
