1 Agricultural Biotechnology Research Center, Academia Sinica, Taipei 11529, Taiwan; and.
2 Department of Plant Pathology and Microbiology, National Taiwan University, Taipei 10617, Taiwan.
Mol Plant Microbe Interact. 2018 Dec;31(12):1257-1270. doi: 10.1094/MPMI-01-18-0012-R. Epub 2018 Oct 3.
Plant viruses cause devastating diseases in plants, yet no effective viricide is available for agricultural application. We screened cultured filtrates derived from various soil microorganisms cultured in vegetable broth that enhanced plant viral resistance. A cultured filtrate, designated F8 culture filtrate, derived from a fungus belonging to the genus Trichosporon, induced strong resistance to various viruses on different plants. Our inoculation assay found the infection rate of Tobacco mosaic virus (TMV)-inoculated Nicotiana benthamiana with F8 culture filtrate pretreatment may decrease to 0%, whereas salicylic acid (SA)-pretreated N. benthamiana attenuated TMV-caused symptoms but remained 100% infected. Tracking Tobacco mosaic virus tagged with green fluorescence protein in plants revealed pretreatment with F8 culture filtrate affected the initial establishment of the virus infection. From F8 culture filtrate, we identified a previously unknown polysaccharide composed of D-mannose, D-galactose, and D-glucose in the ratio 1.0:1.2:10.0 with a α-D-1,4-glucan linkage to be responsible for the induction of plant resistance against viruses through priming of SA-governed immune-responsive genes. Notably, F8 culture filtrate only triggered local defense but was much more effective than conventional SA-mediated systematic acquired resistance. Our finding revealed that microbial cultured metabolites provided a rich source for identification of potent elicitors in plant defense.
植物病毒会导致植物发生严重病害，但目前仍没有有效的植物病毒抑制剂应用于农业。我们筛选了在蔬菜肉汤中培养的各种土壤微生物的培养液，发现其中一些能够增强植物的抗病毒能力。一种来自 Trichosporon 属真菌的培养液（命名为 F8 培养液）能够诱导不同植物对多种病毒产生强烈的抗性。我们的接种实验发现，用 F8 培养液预处理后再接种烟草花叶病毒（TMV），可使感染 Nicotiana benthamiana 的病毒载量降低至 0%，而用水杨酸（SA）预处理的 N. benthamiana 则能减轻 TMV 引起的症状，但仍有 100%的植株被感染。通过在植物中追踪标记有绿色荧光蛋白的烟草花叶病毒，我们发现 F8 培养液预处理会影响病毒感染的初始建立。从 F8 培养液中，我们鉴定出一种以前未知的多糖，其由 D-甘露糖、D-半乳糖和 D-葡萄糖组成，摩尔比为 1.0:1.2:10.0，以α-D-1,4-糖苷键连接，能够通过激活 SA 调控的免疫应答基因来诱导植物抗病毒。值得注意的是，F8 培养液仅触发局部防御，但比传统的 SA 介导的系统性获得抗性更有效。我们的研究结果表明，微生物培养代谢产物为鉴定植物防御中的有效激发子提供了丰富的来源。
