Yamakawa H, Kamada H, Satoh M, Ohashi Y
Institute of Biological Sciences, University of Tsukuba, Tsukuba, Ibaraki 305, Japan (H.Y., H.K.).
Plant Physiol. 1998 Dec;118(4):1213-22. doi: 10.1104/pp.118.4.1213.
Intercellular spaces are often the first sites invaded by pathogens. In the spaces of tobacco mosaic virus (TMV)-infected and necrotic lesion-forming tobacco (Nicotiana tabacum L.) leaves, we found that an inducer for acidic pathogenesis-related (PR) proteins was accumulated. The induction activity was recovered in gel-filtrated fractions of low molecular mass with a basic nature, into which authentic spermine (Spm) was eluted. We quantified polyamines in the intercellular spaces of the necrotic lesion-forming leaves and found 20-fold higher levels of free Spm than in healthy leaves. Among several polyamines tested, exogenously supplied Spm induced acidic PR-1 gene expression. Immunoblot analysis showed that Spm treatment increased not only acidic PR-1 but also acidic PR-2, PR-3, and PR-5 protein accumulation. Treatment of healthy tobacco leaves with salicylic acid (SA) caused no significant increase in the level of endogenous Spm, and Spm did not increase the level of endogenous SA, suggesting that induction of acidic PR proteins by Spm is independent of SA. The size of TMV-induced local lesions was reduced by Spm treatment. These results indicate that Spm accumulates outside of cells after lesion formation and induces both acidic PR proteins and resistance against TMV via a SA-independent signaling pathway.
细胞间隙常常是病原体入侵的首个位点。在感染烟草花叶病毒（TMV）并形成坏死病斑的烟草（Nicotiana tabacum L.）叶片的细胞间隙中，我们发现一种酸性病程相关（PR）蛋白的诱导剂得以积累。诱导活性在具有碱性性质的低分子量凝胶过滤组分中得以恢复， authentic精胺（Spm）被洗脱到该组分中。我们对形成坏死病斑的叶片的细胞间隙中的多胺进行了定量分析，发现游离Spm的水平比健康叶片中高出20倍。在测试的几种多胺中，外源供应的Spm诱导了酸性PR-1基因的表达。免疫印迹分析表明，Spm处理不仅增加了酸性PR-1的积累，还增加了酸性PR-2、PR-3和PR-5蛋白的积累。用水杨酸（SA）处理健康烟草叶片不会导致内源性Spm水平显著增加，并且Spm也不会增加内源性SA的水平，这表明Spm对酸性PR蛋白的诱导独立于SA。Spm处理减小了TMV诱导的局部病斑的大小。这些结果表明，Spm在病斑形成后在细胞外积累，并通过一条不依赖SA的信号通路诱导酸性PR蛋白和对TMV的抗性。
