植物PTI天然免疫信号转导研究进展

病害是危害农业生产的重要因素之一,植物对于病原菌的抗性依赖于植物的天然免疫(plant innate immunity)系统。因此,对于植物天然免疫的研究将为农作物抗病育种提供重要理论基础。植物天然免疫系统包含彼此相互关联的两个层面,即PTI(PAMP-triggered immunity)和ETI(effector-triggered immunity)。近年来,国内外对于PTI的研究取得了一系列重要进展。PTI是由病原物相关分子模式PAMP(pathogen-associated molecular pattern)所诱发的植物免疫反应。PAMP被位于植物细胞表面的受体识别后,将免疫信号通过胞质类受体激酶BIK1(Botrytis-induced kinase 1)、MAPK级联、CDPK(calcium-dependent protein kinase)等向下游传递,诱导活性氧的爆发、气孔的关闭、免疫基因的表达等,从而抑制病原微生物的生长。免疫信号在传递过程中会在多个层次上被精细调控,以保证合适的反应强度和持续时间。本文从植物免疫受体FLS2及其他免疫受体的发现、免疫信号转导组分的发现以及其生物学功能、参与天然免疫的转录因子、植物免疫反应的负调控及植物天然免疫在抗病育种中的应用等方面综述了近年来植物PTI天然免疫的分子机理和信号转导方面的研究进展。并对该领域的发展提出展望,我们认为农作物天然免疫信号转导和作物与致病真菌互作系统的研究将会是未来研究的重点和主要方向,天然免疫的重要理论与基因编辑技术的结合,必将使作物抗病育种迎来新时代。     

望春玉兰扦插育苗试验初报

本文首次报道了望春玉兰扦插育苗试验结果。试验结果表明,选用幼龄植株上的春季营养枝作插条,用自配的生根粉(NIBP)800mg/L溶液速蘸后,插于塑料棚内细沙基质上。保持棚内气温20～25℃,空气相对湿度80%～90%,40～60h后检查,其插条生根率>93%,且根系发达,为快繁和推广辛夷优良品种,提供了科学依据和技术措施。关健词:望春玉兰;扦插育苗;插条生根率     

几丁质触发植物免疫的研究现状与展望

真菌病害是植物病害中最为严重的一种,世界上70%—80%的植物病害都是由真菌引起。几丁质是病原真菌细胞壁的重要组成成分,是一种典型的病原相关分子模式（pathogen-associated molecular pattern,PAMP）。当植物受到病原真菌入侵,位于细胞膜上的模式识别受体（pattern recognition receptor,PRR）能够直接与几丁质及其寡糖相互作用并触发植物的免疫反应。近几年,随着植物几丁质受体的成功鉴定,其与几丁质的相互作用机制以及几丁质触发植物免疫的分子机理被广泛研究,并取得了许多重要进展。为了较全面、系统地反应几丁质触发免疫研究的历史沿革、研究现状和发展趋势,笔者就植物对几丁质的识别机制、信号转导以及病原真菌对几丁质触发的免疫反应的抑制机制这3方面进行了综述,并对未来研究的发展方向进行了探讨。     

Toll样受体9介导的免疫激活研究进展

在细菌和DNA病毒的基因组中广泛存在着以非甲基化的胞嘧啶—鸟嘌呤核苷酸为核心的CpG基序。作为一种病原相关的分子模式（pathogen-associated molecular pattern, PAMP）,含有CpG基序的寡聚脱氧核苷酸（CpG oligodeoxynucleotides,CpG ODN）能激活包括B淋巴细胞和类浆细胞在内的多种免疫细胞,并诱导产生以Th1型细胞免疫反应为主的免疫应答。CpG ODN在哺乳动物细胞中的受体是Toll样受体（Toll-like receptors, TLRs）家族中的Toll样受体 9（TLR9）。TLR9所介导的免疫激活作用在某些传染病的预防、新型疫苗佐剂的开发及过敏性疾病和癌症的治疗中有着巨大的应用前景。     

Nonhost resistance: Self-inflicted DNA damage by fungal DNase accumulation is a major factor in terminating fungal growth in the pea-Fusarium solani f.sp. phaseoli interaction

Pea endocarp tissue generates a total nonhost resistance response against inappropriate pathogens such as the bean pathogen, Fusarium solani f. sp. phaseoli (Fsph) within 6 h. An array of plant components induced include: Pisatin (a phytoalexin), defensins, PR genes and hydrolytic enzymes in the non-host resistance response. This nonhost resistance response is similar but swifter than the responses induced by the compatible true pathogen, F. solani f. sp. pisi (Fspi). It was previously noted that a DNase released by both fungi is involved in induction of these resistance responses within pea endocarp tissue. This report demonstrates the cytological damage that occurs within nuclear DNA of both compatible and incompatible fungi when in contact with pea endocarp tissue and in the presence of DNase activity. The severity of damage to the bean pathogen exceeds that of the pea pathogen and requires only 2 h of contact with the pea tissue to develop. This accumulation of DNA damage is proposed to be the ultimate termination factor in this and other non-host resistance reactions. An updated DNase signaling scheme of the nonhost resistance of pea is presented.     

Simple Bioassay for PAMP-Triggered Immunity in Rice Seedlings Based on Lateral Root Growth Inhibition

Pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) is an essential layer of plant disease resistance. Robust bioassays for PTI are pre-required to dissect its molecular mechanism. In this study, we established that lateral root growth inhibition as a simple and robust measurement of PTI in rice seedlings. Specifically, flg22, a well-characterized PAMP from bacterial flagellin, was used to induce PTI in rice seedlings. While flg22 treatment induced PR gene expression and mitogen-activated protein kinase activation in the roots of rice seedlings to support the PTI triggered, this treatment substantially repressed lateral root growth, but it did not alter primary root growth. Moreover, treatments with chitin (i.e., a fungal PAMP) and oligogalacturonides (i.e., classical damage-associated molecular pattern) clearly inhibited the lateral root growth, although a priming step involving ulvan was required for the chitin treatment. The bioassay developed was applicable to various rice cultivars and wild species. Thus, lateral root growth inhibition represents a simple and reliable assay for studying PTI in rice plants.