NLR及其在植物抗病中的调控作用

为适应丰富多变的生存环境,植物逐渐进化出一套复杂的免疫系统来抵抗病原菌的侵染。核苷酸结合的富含亮氨酸重复蛋白(NLR)作为植物体内普遍存在的一类抗性(R)蛋白,对植物的抗病性具有重要调控作用。该文综述了NLR蛋白结构、信号转导以及对植物抗病的调控作用近几年的研究进展。     

植物NLR基因的表达调控及应用策略

含有一个核酸结合位点以及富含亮氨酸重复序列(nucleotide-binding leucine rich repeats,NLR)类抗性基因在植物免疫中发挥重要作用。该文综述了近年来植物NLR基因的结构和功能特点,在转录、转录后、翻译水平的表达调控,植物NLR基因在增强作物抗性中的应用策略方面的研究进展。植物NLR基因表达调控的研究有助于揭示其分子作用机制,增加对NLR基因信号传导过程的了解;植物NLR基因应用策略的研究在开发抗性作物新品种中有较强的应用价值。     

钙结合蛋白对花粉生长发育调控研究进展

植物钙结合蛋白存在于花粉管中,通过直接或间接结合Ca~(2+),定位膜结构,形成Ca~(2+)信号通道,发生信号转导,对花粉发育及花粉管的生长起到调控作用。目前已明确以钙调蛋白(CAM)、钙依赖型蛋白激酶(CDPK)、类钙调蛋白(CML)、类钙调素B类蛋白(CBL)和激酶蛋白(CIPK)为主的植物钙结合蛋白在调控花粉发育及花粉管生长方面的重要作用。该文主要对近年来国内外已经明确的各类钙结合蛋白家族以及家族成员间不同的作用机理的研究进展进行综述,并举例阐述了钙结合蛋白家族中各类成员对花粉管特定的作用方式及调控作用,最后对今后相关领域的研究前景进行了展望。     

响应植物逆境胁迫的线粒体蛋白研究进展

线粒体是真核细胞的重要细胞器,在植物生长发育以及植物对逆境胁迫的响应方面起着重要的作用。除了线粒体呼吸系统蛋白如线粒体电子传递链(mETC)复合物、交替氧化酶(AOX)和解偶联蛋白(UCP),越来越多的线粒体蛋白如PPR、线粒体热激蛋白(HSC)、一氧化氮合酶相关蛋白(NOA)等被报道参与植物对逆境胁迫的调控过程。本文依次综述了参与植物逆境胁迫的呼吸系统蛋白、PPR蛋白、谷胱甘肽和谷氨酸蛋白酶类蛋白、分子伴侣相关蛋白等线粒体蛋白,并阐述了线粒体蛋白参与的胁迫种类及其分子调控的初步机制,为进一步揭示线粒体蛋白调控植物逆境胁迫的分子机制提供参考。     

开启防御之门: 植物抗病小体

NLR蛋白是存在于植物和动物中的一个免疫受体大家族, 具有核苷酸结合域并富含亮氨酸重复序列。植物NLR通过识别病原菌特异效应子开启免疫信号转导。第1个植物NLR抗性蛋白于25年前克隆, 但其激活机制仍不清楚, 至今仍未获得一个完整的NLR蛋白结构。最近, 柴继杰、周俭民和王宏伟实验室合作解析了第一个植物完整NLR ZAR1激活前后的结构, 研究成果以两篇论文形式发表在“科学”杂志上, 填补了NLR介导的免疫信号转导研究领域的空白。该文简要总结了相关研究进展, 讨论了NLR免疫信号转导研究领域尚需解决的问题。     

开启防御之门:植物抗病小体

NLR蛋白是存在于植物和动物中的一个免疫受体大家族,具有核苷酸结合域并富含亮氨酸重复序列。植物NLR通过识别病原菌特异效应子开启免疫信号转导。第1个植物NLR抗性蛋白于25年前克隆,但其激活机制仍不清楚,至今仍未获得一个完整的NLR蛋白结构。最近,柴继杰、周俭民和王宏伟实验室合作解析了第一个植物完整NLR ZAR1激活前后的结构,研究成果以两篇论文形式发表在"科学"杂志上,填补了NLR介导的免疫信号转导研究领域的空白。该文简要总结了相关研究进展,讨论了NLR免疫信号转导研究领域尚需解决的问题。     

植物胚胎发育MicroRNA研究进展

MicroRNA(miRNA)为长度约22 nt的不编码蛋白的单链新型调控小分子RNA,对植物生长发育和抵抗胁迫等过程具有重要的调控作用。在阐述植物发育中miRNA作用的基础上,进一步介绍植物胚胎发育miRNA的研究进展。     

异三聚体G蛋白在植物非生物胁迫应答中的作用

异三聚体G蛋白(Heterotrimeric GTP-binding proteins)是真核生物中一类重要的信号传导分子,由Gα、Gβ和Gγ3个亚基组成。异三聚体G蛋白不仅参与了植物的生长发育调控,而且还在多种非生物胁迫应答中起着重要的调控作用。本文着重介绍异三聚体G蛋白在植物非生物胁迫应答中的作用及可能的调控机制,并结合当前研究现状对未来研究方向提出展望,以期为今后深入研究异三聚体G蛋白在植物非生物胁迫应答中的调控机制提供参考。     

赤霉素信号转导及其调控植物生长发育的研究进展

赤霉素(Gibberellins或gibberellic acid,GA)是植物生长发育所必需的植物激素之一,调控植物生长发育的多个过程。近年来随着植物分子生物学和功能基因组学的发展,有关GA信号转导途径及其调控植物生长发育的研究取得了一系列的进展。综述了GA信号转导途径的关键组分,包括GA受体GIBBERELLIN INSENSITIVE DWARF1(GID1)蛋白、F-box蛋白(拟南芥中的SLEEPY1[SLY1]和水稻中的GIBBERELLIN INSENSITIVE DWARF2[GID2])及DELLA蛋白,阐述了GA去除DELLA蛋白阻遏作用的分子模型,同时探讨DELLA蛋白通过其互作蛋白整合其它激素及环境信号调控植物生长发育的作用机理。     

异三聚体G蛋白调控植物生长发育功能研究进展北大核心CSCD

异三聚体GTP结合蛋白(G蛋白)是介导真核生物生长发育及逆境响应的关键信号传导组分。动物和植物异三聚体G蛋白由α、β、γ三个亚基组成。近来研究表明,尽管G蛋白核心组分和基本的生化性质在动物和植物中保守,但植物G蛋白表现出新的调控模式。由于G蛋白参与调控植物种子产量、器官大小、生物和非生物胁迫、氮素利用效率等一系列重要的农艺性状,因此对于G蛋白的研究已经成为植物学领域的研究热点。该文对近年来国内外有关植物异三聚体G蛋白的基本组成及结构、动植物G蛋白的作用模式以及G蛋白在植物生长发育过程中的调控作用和植物在逆境胁迫(干旱、温度和盐)响应中的功能等方面的研究进展进行综述,为今后开展植物G蛋白的相关研究提供参考以及为利用G蛋白改良农作物提供理论基础。     

Nucleotide-binding leucine-rich repeat network underlies nonhost resistance of pepper against the Irish potato famine pathogen Phytophthora infestans

Nonhost resistance (NHR) is a robust plant immune response against non-adapted pathogens. A number of nucleotide-binding leucine-rich repeat (NLR) proteins that recognize non-adapted pathogens have been identified, although the underlying molecular mechanisms driving robustness of NHR are still unknown. Here, we screened 57 effectors of the potato late blight pathogen Phytophthora infestans in nonhost pepper (Capsicum annuum) to identify avirulence effector candidates. Selected effectors were tested against 436 genome-wide cloned pepper NLRs, and we identified multiple functional NLRs that recognize P. infestans effectors and confer disease resistance in the Nicotiana benthamiana as a surrogate system. The identified NLRs were homologous to known NLRs derived from wild potatoes that recognize P. infestans effectors such as Avr2, Avrblb1, Avrblb2, and Avrvnt1. The identified CaRpi-blb2 is a homologue of Rpi-blb2, recognizes Avrblb2 family effectors, exhibits feature of lineage-specifically evolved gene in microsynteny and phylogenetic analyses, and requires pepper-specific NRC (NLR required for cell death)-type helper NLR for proper function. Moreover, CaRpi-blb2–mediated hypersensitive response and blight resistance were more tolerant to suppression by the PITG_15 278 than those mediated by Rpi-blb2. Combined results indicate that pepper has stacked multiple NLRs recognizing effectors of non-adapted P. infestans, and these NLRs could be more tolerant to pathogen-mediated immune suppression than NLRs derived from the host plants. Our study suggests that NLRs derived from nonhost plants have potential as untapped resources to develop crops with durable resistance against fast-evolving pathogens by stacking the network of nonhost NLRs into susceptible host plants.     

植物NLR免疫受体的识别、免疫激活与信号调控

高等植物进化出大量膜表面和胞内免疫受体以感知各种病原信号,抵御病原物入侵。其中,细胞表面的模式识别受体感知模式分子后激活基础免疫反应,核苷酸结合和富亮氨酸重复蛋白(NLRs)则通过感知病原微生物分泌的效应蛋白激活特异免疫反应,导致超敏反应与细胞死亡。该文主要综述了NLRs对效应蛋白的识别、植物免疫激活及下游信号调控的最新研究进展。     

Role of pathogen's effectors in understanding host-pathogen interaction

Pathogens can pose challenges to plant growth and development at various stages of their life cycle. Two interconnected defense strategies prevent the growth of pathogens in plants, i.e., molecular patterns triggered immunity (PTI) and pathogenic effector-triggered immunity (ETI) that often provides resistance when PTI no longer functions as a result of pathogenic effectors. Plants may trigger an ETI defense response by directly or indirectly detecting pathogen effectors via their resistance proteins. A typical resistance protein is a nucleotide-binding receptor with leucine-rich sequences (NLRs) that undergo structural changes as they recognize their effectors and form associations with other NLRs. As a result of dimerization or oligomerization, downstream components activate “helper” NLRs, resulting in a response to ETI. It was thought that ETI is highly dependent on PTI. However, recent studies have found that ETI and PTI have symbiotic crosstalk, and both work together to create a robust system of plant defense. In this article, we have summarized the recent advances in understanding the plant's early immune response, its components, and how they cooperate in innate defense mechanisms. Moreover, we have provided the current perspective on engineering strategies for crop protection based on up-to-date knowledge.     

A novel allele of the Arabidopsis thaliana MACPF protein CAD1 results in deregulated immune signaling

Immune recognition in plants is governed by two major classes of receptors: pattern recognition receptors (PRRs) and nucleotide-binding leucine-rich repeat receptors (NLRs). Located at the cell surface, PRRs bind extracellular ligands originating from microbes (indicative of “non-self”) or damaged plant cells (indicative of “infected-self”), and trigger signaling cascades to protect against infection. Located intracellularly, NLRs sense pathogen-induced physiological changes and trigger localized cell death and systemic resistance. Immune responses are under tight regulation in order to maintain homeostasis and promote plant health. In a forward-genetic screen to identify regulators of PRR-mediated immune signaling, we identified a novel allele of the membrane-attack complex and perforin (MACPF)-motif containing protein CONSTITUTIVE ACTIVE DEFENSE 1 (CAD1) resulting from a missense mutation in a conserved N-terminal cysteine. We show that cad1-5 mutants display deregulated immune signaling and symptoms of autoimmunity dependent on the lipase-like protein ENHANCED DISEASE SUSCEPTIBILITY 1 (EDS1), suggesting that CAD1 integrity is monitored by the plant immune system. We further demonstrate that CAD1 localizes to both the cytosol and plasma membrane using confocal microscopy and subcellular fractionation. Our results offer new insights into immune homeostasis and provide tools to further decipher the intriguing role of MACPF proteins in plants.     

Nucleotide‐binding resistance gene signatures in sugar beet,insights from a new reference genome

Nucleotide‐binding (NB‐ARC), leucine‐rich‐repeat genes (NLRs) account for 60.8% of resistance (R) genes molecularly characterized from plants. NLRs exist as large gene families prone to tandem duplication and transposition, with high sequence diversity among crops and their wild relatives. This diversity can be a source of new disease resistance, but difficulty in distinguishing specific sequences from homologous gene family members hinders characterization of resistance for improving crop varieties. Current genome sequencing and assembly technologies, especially those using long‐read sequencing, are improving resolution of repeat‐rich genomic regions and clarifying locations of duplicated genes, such as NLRs. Using the conserved NB‐ARC domain as a model, 231 tentative NB‐ARC loci were identified in a highly contiguous genome assembly of sugar beet, revealing diverged and truncated NB‐ARC signatures as well as full‐length sequences. The NB‐ARC‐associated proteins contained NLR resistance gene domains, including TIR, CC and LRR, as well as other integrated domains. Phylogenetic relationships of partial and complete domains were determined, and patterns of physical clustering in the genome were evaluated. Comparison of sugar beet NB‐ARC domains to validated R‐genes from monocots and eudicots suggested extensive Beta vulgaris‐specific subfamily expansions. The NLR landscape in the rhizomania resistance conferring Rz region of Chromosome 3 was characterized, identifying 26 NLR‐like sequences spanning 20 MB. This work presents the first detailed view of NLR family composition in a member of the Caryophyllales, builds a foundation for additional disease resistance work in B. vulgaris, and demonstrates an additional nucleic‐acid‐based method for NLR prediction in non‐model plant species.     

Molecular insights into the biochemical functions and signalling mechanisms of plant NLRs

Plant intracellular immune receptors known as NLR (nucleotide-binding leucine-rich repeat) proteins confer immunity and cause cell death. Plant NLR proteins that directly or indirectly recognize pathogen effector proteins to initiate immune signalling are regarded as sensor NLRs. Some NLR protein families function downstream of sensor NLRs to transduce immune signalling and are known as helper NLRs. Recent breakthrough studies on plant NLR protein structures and biochemical functions greatly advanced our understanding of NLR biology. Comprehensive and detailed knowledge on NLR biology requires future efforts to solve more NLR protein structures and investigate the signalling events between sensor and helper NLRs, and downstream of helper NLRs.     

The proteasome regulator PTRE1 contributes to the turnover of SNC1 immune receptor

Plants have evolved a sophisticated immune system in order to recognize and respond to microbes in their environments. Nucleotide-binding leucine-rich repeat (NLR) proteins detect the presence of specific effector molecules delivered into host cells by pathogens and activate strong defence responses. However, as excessive accumulation of NLRs can result in inappropriate immune responses, their abundance must be tightly regulated. Targeted degradation of NLRs through the ubiquitin proteasome pathway is an important mechanism to limit NLR accumulation. Mutations that perturb NLR degradation can cause autoimmune phenotypes. In this study, we show that the proteasome regulator PTRE1 also contributes to NLR degradation. ptre1 mutant plants exhibit increased defence marker gene expression and enhanced disease resistance against virulent pathogens. The stability of the NLR, SUPPRESSOR OF npr1-1 CONSTITUTIVE 1 (SNC1) is also increased in the ptre1 mutant. Although the mouse homologue of PTRE1 was reported to interact with a Cell Division Control protein 48 (CDC48) homologue in vitro (Clemen et al., 2015), we only observed interaction between PTRE1 and AtCDC48A in a split luciferase assay, but not in co-immunoprecipitation. In addition, a related Arabidopsis protein PTRE1h shares partial redundancy with PTRE1. Together, PTRE1 acts as a negative regulator of plant immunity partly by facilitating the degradation of immune receptors such as SNC1.