University of Graz, Institute of Plant Sciences, Schubertstrasse 51, 8010 Graz, Austria.
Mol Plant Microbe Interact. 2010 Nov;23(11):1448-59. doi: 10.1094/MPMI-05-10-0117.
Sulfur-induced resistance, also known as sulfur-enhanced defense (SIR/SED) was investigated in Nicotiana tabacum cv. Samsun nn during compatible interaction with Tobacco mosaic virus (TMV) in correlation with glutathione metabolism. To evaluate the influence of sulfur nutritional status on virus infection, tobacco plants were treated with nutrient solutions containing either sufficient sulfate (+S) or no sulfate (-S). Sufficient sulfate supply resulted in a suppressed and delayed symptom development and diminished virus accumulation over a period of 14 days after inoculation as compared with -S conditions. Expression of the defense marker gene PR-1a was markedly upregulated in sulfate-treated plants during the first day after TMV inoculation. The occurrence of SIR/SED correlated with a higher level of activity of sulfate assimilation, cysteine, and glutathione metabolism in plants treated with sulfate. Additionally, two key genes involved in cysteine and glutathione biosynthesis (encoding adenosine 5'-phosphosulfate reductase and γ-glutamylcysteine synthetase, respectively) were upregulated within the first day after TMV inoculation under +S conditions. Sulfate withdrawal from the soil was accelerated at the beginning of the infection, whereas it declined in the long term, leading to an accumulation of sulfur in the soil of plants grown with sulfate. This observation could be correlated with a decrease in sulfur contents in TMV-infected leaves in the long term. In summary, this is the first study that demonstrates a link between the activation of cysteine and glutathione metabolism and the induction of SIR/SED during a compatible plant-virus interaction in tobacco plants, indicating a general mechanism behind SIR/SED.
硫诱导抗性，也称为硫增强防御（SIR/SED），在与烟草花叶病毒（TMV）相容的相互作用中，在与谷胱甘肽代谢相关的情况下，在 Nicotiana tabacum cv. Samsun nn 中进行了研究。为了评估硫营养状况对病毒感染的影响，用含有足够硫酸盐（+S）或无硫酸盐（-S）的营养液处理烟草植物。与 -S 条件相比，充足的硫酸盐供应导致接种后 14 天内症状发展受到抑制和延迟，病毒积累减少。与 TMV 接种后第一天相比，硫酸盐处理的植物中防御标记基因 PR-1a 的表达明显上调。SIR/SED 的发生与硫酸盐处理植物中亚硫酸盐同化、半胱氨酸和谷胱甘肽代谢活性的提高相关。此外，在 +S 条件下，与半胱氨酸和谷胱甘肽生物合成相关的两个关键基因（分别编码腺苷 5'-磷酸硫酸还原酶和γ-谷氨酰半胱氨酸合酶）在 TMV 接种后的第一天就被上调。感染开始时，土壤中的硫酸盐被加速提取，而长期来看则下降，导致在硫酸盐处理的植物土壤中积累了硫。这一观察结果可能与长期感染 TMV 的叶片中硫含量的减少有关。总之，这是首次研究表明，在烟草植物中，半胱氨酸和谷胱甘肽代谢的激活与相容性植物-病毒相互作用中 SIR/SED 的诱导之间存在联系，表明 SIR/SED 背后存在一种普遍机制。
