Peptidoglycan from Fermentation By-Product Triggers Defense Responses in Grapevine

Plants are constantly under attack from a variety of microorganisms, and rely on a series of complex detection and response systems to protect themselves from infection. Here, we found that a by-product of glutamate fermentation triggered defense responses in grapevine, increasing the expression of defense response genes in cultured cells, foliar chitinase activity, and resistance to infection by downy mildew in leaf explants. To identify the molecule that triggered this innate immunity, we fractionated and purified candidates extracted from Corynebacterium glutamicum, a bacterium used in the production of amino acids by fermentation. Using hydrolysis by lysozyme, a silkworm larva plasma detection system, and gel filtration analysis, we identified peptidoglycan as inducing the defense responses. Peptidoglycans of Escherichia coli, Bacillus subtilis, and Staphylococcus aureus also generated similar defensive responses.

植物始终处于各类微生物的侵袭威胁之下，依赖一套复杂的感知与防御响应系统抵御侵染。本研究发现，谷氨酸发酵的副产物可诱导葡萄产生防御响应，具体体现为提升培养细胞中防御响应基因的表达量、叶片几丁质酶活性，以及叶外植体对霜霉病侵染的抗性。为鉴定触发该先天免疫的活性分子，我们对从谷氨酸棒杆菌（Corynebacterium glutamicum，一种发酵法生产氨基酸的常用细菌）中提取的候选组分进行分级分离与纯化。通过溶菌酶（lysozyme）水解实验、家蚕幼虫血浆检测体系及凝胶过滤分析，我们鉴定出肽聚糖（peptidoglycan）可诱导此类防御响应。大肠杆菌（Escherichia coli）、枯草芽孢杆菌（Bacillus subtilis）与金黄色葡萄球菌（Staphylococcus aureus）的肽聚糖同样可引发相似的防御反应。