植物病原真菌过氧化物酶体的发生机制及功能

过氧化物酶体（peroxisome,P）是真核细胞中普遍存在的细胞器,参与多种重要的代谢过程。P的产生、增殖及降解是细胞器发生机理研究的重要部分。到目前已知的P发生相关基因有30多个,但其机制仍不完全清楚。作为一种多细胞真核生物,丝状真菌在P发生机制的研究中有重要价值。近年来,随着基因组序列的应用和真菌生物技术的进展,丝状真菌中P功能及发生机制的研究取得了较大进展。同时,作为丝状真菌真菌中的重要类群,植物病原真菌P在致病过程中的作用也引起关注。本文对P发生机制、在丝状真菌中的研究概况,以及与植物病原真菌致病性的关系进行了 综述。     

灰葡萄孢菌过氧化物酶体及细胞核的荧光蛋白标记

[目的]对灰葡萄孢菌(Botrytis cinerea)的细胞核和过氧化物酶体进行荧光蛋白标记,为研究其生长发育和侵染过程中细胞结构和细胞器动态提供基础.[方法]以绿色荧光蛋白(GFP)和红色荧光蛋白(DsRED、mCherry)为报告基因,利用根癌农杆菌介导转化(Agrobacterium tumefaciens m...     

酵母过氧化物酶体的形成机制

过氧化物酶体是细胞中一种重要的细胞器.过氧化物酶体在细胞功能的发挥和人体健康方面有着重要作用.目前,以酵母过氧化物酶体为模型,研究过氧化物酶体的形成机制是研究热点.从过氧化物酶体起源、生成方式介绍最新研究进展,总结在酵母细胞中参与过氧化物酶体形成的必需基因(pex),及其编码Peroxin蛋白在过氧化物酶体形成过程中的...     

过氧化物酶体功能异常与阿尔茨海默病

过氧化物酶体是一种广泛存在于真核细胞内的异质性细胞器,具有多种酶活性,主要功能是参与脂肪酸氧化、磷脂合成和氧化应激平衡的调节等过程。研究发现,过氧化物酶体功能异常引起的脑组织中极长链脂肪酸聚集、植烷酸贮积、二十二碳六烯酸(docosahexaenoic acid,DHA)和缩醛磷脂减少等与阿尔茨海默病(Alzheimer’s disease,AD)的发生发展密切相关。尽管具体的机制尚不清楚,但目前认为,过氧化物酶体功能异常很可能是AD发生发展的始动因素之一。因此,就过氧化物酶体功能异常与AD之间关系的研究进展进行综述,有助于为AD的发病机制研究提供线索和依据。     

过氧化物酶体与病原真菌的致病性

过氧化物酶体(Peroxisome)是一类单层膜的细胞器,普遍存在于各种真核细胞中。过氧化物酶体是丰富的酶库,含有至少50种酶类,参与生物体的多种生理代谢过程,如乙醛酸循环、脂肪酸的β-氧化及活性氧的调节等。近年来,日益增多的研究表明过氧化物酶体和病原真菌的乙醛酸循环及脂肪酸的β-氧化功能的发挥密切相关,并影响病原真菌的致病性。总结过氧化物酶体中酶的种类和功能,评述过氧化物酶体与乙醛酸循环、脂肪酸β-氧化和病原真菌致病性的关系。     

过氧化物酶体增生激活型受体γ与AS

过氧化物酶体增生激活型受体γ（PPARγ）在组织中较为广泛地表达,主要是调节脂肪细胞分化、糖稳态,为噻唑烷二酮类抗糖尿病药物的生物学受体。PPARγ表达增强或激活可调节脂质代谢,抑制单核／巨噬细胞功能,减少细胞粘附分子和其他炎症介质的产生和释放,并抑制血管平滑肌产殖和迁移;可能改善某些动脉粥样硬化（atherosclerosis,AS)的危险因素,在AS的发生发展过程中具有重要意义。     

大鼠肝细胞过氧化物酶体的提取

:采用蔗糖密度梯度离心法 ( 950 0 0× g,2 h)提取大鼠肝细胞过氧化物酶体 ,所得过氧化物酶体形态完整 ,纯度与肝匀浆相比提高了 2 6倍 ,仅有少量 ( 0 .5%～ 0 .9%)的微粒体和线粒体污染 ,回收率为 1 2 %。为研究过氧化物酶体提供了有效的分离方法。此法还可将过氧化物酶体、微粒体、线粒体同时进行分离。     

莲子草假隔链格孢SF 193菌株的复壮对其产孢量和致病性的影响

【背景】莲子草假隔链格孢是空心莲子草的重要生防菌,但长时间保存或继代培养会导致该菌株产孢量和致病性显著下降。【方法】通过对初始菌株回接、分离、纯化和鉴定相继获得复壮一代和二代菌株,分别在3、6、9d后对初始菌株、复壮一代和二代菌株进行产孢培养,比较其产孢量;同时比较分析了这3代菌株的液体发酵原液和1:10稀释液对空心莲子草的防除效果。【结果】获得了10株复壮一代和10株复壮二代菌株,20株菌对空心莲子草均有致病作用,且产生的分生孢子形态特征与初始菌株一致。与初始菌株相比,复壮菌株的产孢量显著提高且达到最大产孢量的时间显著短于初始菌株。其中,复壮二代菌株的孢子量是初始菌株的4.8倍,其次为复壮一代菌株,产孢量是初始菌株的4.1倍;复壮菌株达到最大产孢量的时间为3d,初始菌株为6d。复壮菌株一代和二代的原液对空心莲子草的致病性分别比初始菌株提高了4.65%和9.82%,1:10稀释液的致病性分别提高了25.79%和16.55%。【结论与意义】对长期保存或继代培养的空心莲子草生防菌复壮可显著提高其产孢量和致病性,对维持生防菌遗传性状的稳定性和提高对空心莲子草的防效具有重要意义。     

过氧化物酶体的稳态维持机制与膜接触位点

过氧化物酶体是保守存在于真核生物中的一种细胞器,参与多种生化代谢过程,包括脂肪酸β氧化反应、活性氧的产生和降解等。过氧化物酶体在生物发生和应对环境胁迫过程中,通过数量和时空分布的规律性动态变化,实现质量控制,以维持其生化代谢的稳态,从而保持机体的正常生命活动。同时,作为真核细胞的代谢枢纽,过氧化物酶体功能的正常发挥与稳态维持需要与其他细胞器相互协作。过氧化物酶体膜接触位点在过氧化物酶体与各细胞器相互连接和交流中发挥着重要作用。近年来,过氧化物酶体稳态维持机制和膜接触位点的组成和功能成为国内外相关研究的热点,本文对相关研究的进展进行了综述。     

锰过氧化物酶的结构与功能

综述了木素降解的关键酶之一锰过氧化物酶的三维分子结构和催化反应性能,综合概述了通过定点诱变等方法对锰过氧化物酶的结构和功能的研究进展。     

Microbial Transformation of 14‐Anhydrodigoxigenin by Alternaria alternata

The microbial transformation of 14‐anhydrodigoxigenin ( 1 ) by Alternaria alternata CGMCC 3.577 led to the production of seven new metabolites, 2 – 8 . Their structures were determined by extensive spectroscopic (CD, IR, 1D‐ and 2D‐NMR, and HR‐ESI‐MS) data analyses. The reactions in the bioprocess exhibited diversity, including specific oxidation, hydroxylation, reduction, epoxidation, and dehydration. In addition, a hypothetical biocatalytic pathway is proposed.     

Genomic features and evolution of the conditionally dispensable chromosome in the tangerine pathotype of Alternaria alternata

The tangerine pathotype of the ascomycete fungus Alternaria alternata is the causal agent of citrus brown spot, which can result in significant losses of both yield and marketability for tangerines worldwide. A conditionally dispensable chromosome (CDC), which harbours the host-selective ACT toxin gene cluster, is required for tangerine pathogenicity of A. alternata. To understand the genetic makeup and evolution of the tangerine pathotype CDC, we isolated and sequenced the CDCs of the A. alternata Z7 strain and analysed the function and evolution of their genes. The A. alternata Z7 strain has two CDCs (~1.1 and ~0.8 Mb, respectively), and the longer Z7 CDC contains all but one contig of the shorter one. Z7 CDCs contain 254 predicted protein-coding genes, which are enriched in functional categories associated with ‘metabolic process’ (55 genes, P = 0.037). Relatively few of the CDC genes can be classified as carbohydrate-active enzymes (CAZymes) (4) and transporters (19) and none as kinases. Evolutionary analysis of the 254 CDC proteins showed that their evolutionary conservation tends to be restricted within the genus Alternaria and that the CDC genes evolve faster than genes in the essential chromosomes, likely due to fewer selective constraints. Interestingly, phylogenetic analysis suggested that four of the 25 genes responsible for the ACT toxin production were likely transferred from Colletotrichum (Sordariomycetes). Functional experiments showed that two of them are essential for the virulence of the tangerine pathotype of A. alternata. These results provide new insights into the function and evolution of CDC genes in Alternaria.     

链格孢菌毒素对紫茎泽兰的致病机理

以叶圆片法分析链格孢菌[Alternaria alternata(Fr.)Keissler]毒素对紫茎泽兰（Eupatorium adenophorum Spreng.)叶组织细胞膜透性、过氧化物酶（POD）、抗坏血酸过氧化物酶（APX）和过氧化氢酶（CAT）活性以及丙二醛（MDA）含量的影响,结果表明,链格孢菌毒素使紫茎泽兰叶组织细胞膜透性上升,Na^ 和K^ 渗漏量增加,膜脂过氧化加强,MDA含量上升;链格孢菌毒素处理的紫茎泽兰叶片中POD、APX和CAT的活性均较对照降低。     

Interactions of Apple and the Alternaria alternata Apple Pathotype

Apple is one of the most cultivated tree fruits worldwide, and is susceptible to many diseases. Understanding the interactions between the host and pathogen is critical in implementing disease management strategies and developing resistant cultivars. This review provides an update on the interactions of apple with Alternaria alternata apple pathotype, which causes Alternaria blotch, with a brief history about the discovery of the disease and pathogen and its damage and epidemiology. The focus of the review is placed on the physiological and genetic response of the host to pathogen infection, including resistance and susceptibility, and the molecular markers associated with them. Of the response of the pathogen to the host, the emphasis is placed on the role of the selective toxins on pathogenicity and their genetic controls and regulations. The review ends with a perspective on future directions in the research on the apple-A. alternata pathosystem in the era of genomics and post genomics, particularly on how to identify candidate genes from both host and pathogen for potential genetic engineering for disease resistant cultivars.     

Pex14/17, a filamentous fungus‐specific peroxin,is required for the import of peroxisomal matrix proteins and full virulence of Magnaporthe oryzae

Peroxisomes are ubiquitous organelles in eukaryotic cells that fulfil a variety of biochemical functions. The biogenesis of peroxisomes requires a variety of proteins, named peroxins, which are encoded by PEX genes. Pex14/17 is a putative recently identified peroxin, specifically present in filamentous fungal species. Its function in peroxisomal biogenesis is still obscure and its roles in fungal pathogenicity have not yet been documented. Here, we demonstrate the contributions of Pex14/17 in the rice blast fungus Magnaporthe oryzae (Mopex14/17) to peroxisomal biogenesis and fungal pathogenicity by targeting gene replacement strategies. Mopex14/17 has properties of both Pex14 and Pex17 with regard to its protein sequence. Mopex14/17 is distributed at the peroxisomal membrane and is essential for efficient peroxisomal targeting of proteins containing peroxisomal targeting signal 1. MoPEX19 deletion leads to the cytoplasmic distribution of Mopex14/17, indicating that the peroxisomal import of Pex14/17 is dependent on Pex19. The knockout mutants of MoPEX14/17 show reduced fatty acid utilization, reactive oxygen species (ROS) degradation and cell wall integrity. Moreover, Δmopex14/17 mutants show delayed conidial generation and appressorial formation, and a reduction in appressorial turgor accumulation and penetration ability in host plants. These defects result in a significant reduction in the virulence of the mutant. These data indicate that MoPEX14/17 plays a crucial role in peroxisome biogenesis and contributes to fungal development and pathogenicity.     

A cAMP‐Dependent Protein Kinase Gene,aapk1, Is Required for Mycelia Growth,Toxicity and Pathogenicity of Alternaria alternata on Tobacco

The fungus Alternaria alternata is a common spot‐producing plant pathogen. During the past decade, tobacco brown spot disease caused by this fungus has became prevalent in China and lead to significant losses. To better understand the molecular pathogenesis of this fungus, the aapk1 gene encoding a cAMP‐dependent protein kinase catalytic subunit was cloned, sequenced and characterized. The aapk1 deletion mutants were identified from hygromycin‐resistant transformants by PCR strategy and confirmed by Southern blot analysis and RT‐PCR. The aapk1 deletion mutant exhibited reduced vegetative growth and was less toxic than the wild‐type strain sd1. Deletion of aapk1 also delayed disease development on detached tobacco leaves. Thus, we propose that the cAMP signalling pathway is involved in mycelia growth and pathogenic phenotype of Alternaria alternata.     

链格孢菌毒素合成相关基因研究进展

链格孢属真菌(Alternaria Nees)是世界上分布最广泛的真菌之一,可产生9种寄主选择性毒素(host-selective toxins,HST)。根据寄主不同,将链格孢属的7个生理小种称为链格孢菌(Alternaria alternata)的7种致病型。每种致病型产生的HST都是低分子质量的次级代谢产物,只对敏感品种有毒,对抗性品种无毒。参与HST生物合成的基因都是多拷贝的,这些共同表达的基因组成基因簇。各致病型的基因簇位于一条小于2.0Mb的conditionally dispensable(CD)染色体上,CD染色体的不稳定性不影响菌丝的生长和孢子的萌发,但与菌株的致病力有关。从链格孢菌6种致病型得到毒素合成基因,日本梨致病型、草莓致病型、橘致病型有共同的EDA结构域,这3种致病型有很多EDA生物合成需要的同源基因。HST的分子遗传学研究为链格孢菌不同致病型的演化提供了新的见解。     

柠檬醛熏蒸对互隔交链孢生长及其产毒的抑制作用

互隔交链孢是一种重要的能产生交链孢酚（AOH）等真菌毒素的植物病原菌。精油是重要的抑制病原菌侵染的挥发性植物提取物,其活性组分包括柠檬醛等。本研究表明柠檬醛可高效地抑制互隔交链孢的生长和AOH毒素的产生。柠檬醛熏蒸能够引起互隔交链孢菌丝断裂影响其延伸,而对其分生孢子结构的影响不明显。柠檬醛能够引起互隔交链孢活性氧生成的紊乱,这可能是导致AOH显著下降的原因之一。由于柠檬醛能高效抑制互隔交链孢生长和产毒,因此其可作为传统熏蒸剂的潜在替代品,以防控互隔交链孢引起的病害以及毒素污染。柠檬醛抑制互隔交链孢生长产毒的研究为其开发与应用奠定了良好的基础。