The sulfated laminarin triggers a stress transcriptome before priming the SA- and ROSdependent defenses during grapevine's induced resistance against Plasmopara viticola

Cultivated grapevine (Vitis vinifera) is susceptible to many pathogens which cause significant losses to viticulture worldwide. Chemical control is available, but agro-ecological concerns have raised interest in alternative methods, especially in elicitation of plant immunity by bio-molecules such as Pathogen Associated Molecular Patterns (PAMPs). We have demonstrated that the beta-glucan laminarin (Lam) and its sulfated derivative (PS3) induce a PAMP-triggered immunity in grapevine against downy mildew (Plasmopara viticola). However, if Lam elicits classical grapevine defenses, PS3 triggered grapevine resistance via a poorly understood priming phenomenon. The aim of this study was to discover the mechanism of the PS3-induced resistance. On uninfected grapevine, we first investigated defense signaling and performed microarray experiments to identify early events and genes directly triggered by PS3. Our results showed that PS3 i) was unable to elicit ROS and NO production, cytosolic Ca2+ variations, MAPK activation but triggered a long lasting plasma membrane depolarization in grapevine cells ii) up-regulated a stress-responsive transcriptome close to the one induced by Lam but only partly overlapping the ones triggered by salicylate (SA) or jasmonate (JA). Finally, in response to P. viticola infection, PS3 specifically primed the SA- and ROS-dependent defense pathways leading to grapevine triggered immunity against this biotroph. Keywords: cell death, induced resistance, oomycete, priming, reactive oxygen species, salicylate, sulfated laminarin, transcriptomics, Vitis vinifera. 6 samples (Adj, PS3, Lam, ctrl, SA, JA) were analized with 3 biological replicates each, Adj and ctrl samples are reference samples

栽培葡萄（Vitis vinifera）易受多种病原菌侵染，给全球葡萄种植业造成了严重的经济损失。化学防治虽可实施，但农业生态层面的顾虑引发了人们对替代防治手段的关注，尤其是利用病原相关分子模式（Pathogen Associated Molecular Patterns, PAMPs）这类生物分子激发植物免疫。本团队此前已证实，β-葡聚糖昆布多糖（laminarin, Lam）及其硫酸化衍生物PS3，可诱导葡萄产生针对葡萄霜霉病（Plasmopara viticola）的PAMPs触发免疫（PAMP-triggered immunity）。与之不同的是，昆布多糖仅能激发葡萄产生经典防御反应，而PS3则通过一种尚不明确的启动（priming）现象介导葡萄抗病性。本研究旨在阐明PS3诱导抗病性的具体分子机制。

我们首先在未受侵染的葡萄植株中开展防御信号通路研究，并进行微阵列（microarray）实验，以筛选PS3直接触发的早期事件与相关功能基因。研究结果显示：其一，PS3无法诱导活性氧（reactive oxygen species, ROS）与一氧化氮（NO）的产生、胞质钙离子（Ca²+）浓度波动以及丝裂原活化蛋白激酶（mitogen-activated protein kinase, MAPK）的激活，但可在葡萄细胞中引发持久的质膜去极化；其二，PS3上调的胁迫响应转录组与昆布多糖诱导的转录组较为接近，但仅与水杨酸（salicylate, SA）或茉莉酸（jasmonate, JA）介导的转录组存在部分重叠。

最终，在遭遇葡萄霜霉菌侵染时，PS3可特异性启动SA与ROS依赖的防御通路，从而赋予葡萄针对该活体营养型病原菌的触发免疫。

关键词：细胞死亡、诱导抗病性、卵菌、启动（priming）、活性氧、水杨酸、硫酸化昆布多糖、转录组学、栽培葡萄（Vitis vinifera）。

本研究共对6组样本（Adj、PS3、Lam、ctrl、SA、JA）进行检测，每组均设置3次生物学重复，其中Adj与ctrl为参照样本。