1 Institute for Biology and Biotechnology of Plants, University of Münster, Schlossplatz 8, 48143 Münster, Germany; and.
2 Institute for Physical Chemistry, University of Münster, Corrensstraße 30, 48149 Münster, Germany.
Mol Plant Microbe Interact. 2018 Nov;31(11):1145-1153. doi: 10.1094/MPMI-04-18-0098-R. Epub 2018 Sep 5.
Chitin, a linear polymer of N-acetyl-d-glucosamine, and chitosans, fully or partially deacetylated derivatives of chitin, are known to elicit defense reactions in higher plants. We compared the ability of chitin and chitosan oligomers and polymers (chitin oligomers with degree of polymerization [DP] 3 to 8; chitosan oligomers with degree of acetylation [DA] 0 to 35% and DP 3 to 15; chitosan polymers with DA 1 to 60% and DP approximately 1,300) to elicit an oxidative burst indicative of induced defense reactions in Arabidopsis thaliana seedlings. Fully deacetylated chitosans were not able to trigger a response; elicitor activity increased with increasing DA of chitosan polymers. Partially acetylated chitosan oligomers required a minimum DP of 6 and at least four N-acetyl groups to trigger a response. Invariably, elicitation of an oxidative burst required the presence of the chitin receptor AtCERK1. Our results as well as previously published studies on chitin and chitosan perception in plants are best explained by a new general model of LysM-containing receptor complexes in which two partners form a long but off-set chitin-binding groove and are, thus, dimerized by one chitin or chitosan molecule, sharing a central GlcNAc unit with which both LysM domains interact. To verify this model and to distinguish it from earlier models, we assayed elicitor and inhibitor activities of selected partially acetylated chitosan oligomers with fully defined structures. In contrast to the initial 'continuous groove', the original 'sandwich', or the current 'sliding mode' models for the chitin/chitosan receptor, the here-proposed 'slipped sandwich' model-which builds on these earlier models and represents a consensus combination of these-is in agreement with all experimental observations.
几丁质是一种 N-乙酰-d-葡萄糖胺的线性聚合物，壳聚糖是几丁质的完全或部分脱乙酰化衍生物，已知它们能引起高等植物的防御反应。我们比较了几丁质和壳聚糖低聚物和聚合物（聚合度[DP]为 3 到 8 的几丁质低聚物；乙酰化度[DA]为 0 到 35%和 DP 为 3 到 15 的壳聚糖低聚物；DA 为 1 到 60%和 DP 约为 1300 的壳聚糖聚合物）引发拟南芥幼苗氧化爆发的能力，表明诱导防御反应。完全脱乙酰壳聚糖不能引发反应；壳聚糖聚合物的 DA 增加，其激发活性增加。部分乙酰化壳聚糖低聚物需要 DP 至少为 6，至少有四个 N-乙酰基才能引发反应。不变的是，氧化爆发的激发需要几丁质受体 AtCERK1 的存在。我们的结果以及以前关于植物中几丁质和壳聚糖感知的研究最好用一种新的含 LysM 的受体复合物的一般模型来解释，其中两个伴侣形成一个长但偏移的几丁质结合槽，因此由一个几丁质或壳聚糖分子二聚化，共享一个中央 GlcNAc 单元，两个 LysM 结构域与之相互作用。为了验证这个模型，并将其与早期模型区分开来，我们用具有完全定义结构的选定部分乙酰化壳聚糖低聚物测定了诱导剂和抑制剂的活性。与最初的“连续槽”、原始的“三明治”或当前的“滑动模式”几丁质/壳聚糖受体模型相比，这里提出的“滑动三明治”模型——基于这些早期模型，是这些模型的共识组合——与所有实验观察结果一致。
