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《The Plant Cell》:解析水稻天然免疫作用机制 
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发布时间:2012-8-31 10:22:13

日前,《The Plant Cell》在线发表了中山大学生命科学学院的最新研究成果。这篇题为“Lysin Motif-Containing Proteins LYP4 and LYP6 Play Dual Roles in Peptidoglycan and Chitin Perception in Rice Innate Immunity”论文表明,研究人员发现了两个水稻同源赖氨酸结构域蛋白:LYP4 和LYP6能感应细菌肽聚糖PGN结构,以及真菌几丁质结构,作为模式识别受体PRRs,在水稻天然免疫调控中扮演重要作用的模式识别受体,并解析了这两个受体的作用机制。这项研究证明了LYP4 和LYP6在水稻天然免疫调控中的关键作用,指出了这两种蛋白能作为PGN和几丁质的混杂模式识别受体,从而为进一步探讨植物天然免疫提供了宝贵的资料。

植物的天然免疫是植物免疫系统的重要组成部分,植物能通过细胞表面免疫受体和胞内免疫受体感受来源于病原微生物的分子,激活天然免疫,抵御病原物的侵染。这些存在于植物细胞膜上的受体能通过识别病原体上的一些共有的、保守的分子基序(也即病原相关分子模式),引发先天免疫反应。

研究人员通过活细胞成像和microsomal fractionation,找到了这些蛋白在水稻细胞中的细胞膜定位,并且发现当细胞接触到细菌病原体,或者不同的微生物相关分子模式(microbe-associated molecular patterns ,MAMPs)时,能快速诱导编码这两个蛋白的基因转录。

除此之外,研究人员还发现体外LYP4 和LYP6能选择性结合在肽聚糖和几丁质上,而不能结合脂多糖,因此沉默这两个基因之一,会特异性造成水稻中PGN-,或者几丁质-诱导的防御应答,比如活性氧的生成,防御基因的激活,胼胝质沉积等,从而无法抵抗水稻白叶枯病菌,以及真菌稻瘟病菌的侵袭,但并不会影响到LPS相关的应答。

有趣的是,研究人员发现用过量的PGN进行预处理,会造成水稻细胞对几丁质,而不是鞭毛碱化应答的大幅度下降,相反几丁质的预处理,则会引起细胞对PGN应答灵敏度降低,这说明PGN和几丁质在水稻中有重叠的感应元件。

论文摘要:

Plant innate immunity relies on successful detection of microbe-associated molecular patterns (MAMPs) of invading microbes via pattern recognition receptors (PRRs) at the plant cell surface. Here, we report two homologous rice (Oryza sativa) lysin motif–containing proteins, LYP4 and LYP6, as dual functional PRRs sensing bacterial peptidoglycan (PGN) and fungal chitin. Live cell imaging and microsomal fractionation consistently revealed the plasma membrane localization of these proteins in rice cells. Transcription of these two genes could be induced rapidly upon exposure to bacterial pathogens or diverse MAMPs. Both proteins selectively bound PGN and chitin but not lipopolysaccharide (LPS) in vitro. Accordingly, silencing of either LYP specifically impaired PGN- or chitin- but not LPS-induced defense responses in rice, including reactive oxygen species generation, defense gene activation, and callose deposition, leading to compromised resistance against bacterial pathogen Xanthomonas oryzae and fungal pathogen Magnaporthe oryzae. Interestingly, pretreatment with excess PGN dramatically attenuated the alkalinization response of rice cells to chitin but not to flagellin; vice versa, pretreatment with chitin attenuated the response to PGN, suggesting that PGN and chitin engage overlapping perception components in rice. Collectively, our data support the notion that LYP4 and LYP6 are promiscuous PRRs for PGN and chitin in rice innate immunity.

详细信息:

http://www.cnrri.cn/zjww/Detail.aspx?id=20022635

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