致病疫霉RXLR效应蛋白相关研究进展

由致病疫霉(Phytophthora infestans(Mont.)de Bary)引起的晚疫病是马铃薯生产中最具毁灭性的病害。为了成功入侵和在寄主植物中繁衍,致病疫霉会向寄主细胞分泌一类RXLR效应蛋白以干扰植物免疫系统。自2005年克隆第一个晚疫病菌RXLR类无毒基因AVR3a以来,国内外学者从RXLR效应蛋白的结构、功能,以及与寄主靶标作用机理等多个方面展开了大量研究。随着高通量测序技术与效应子组学技术的发展,RXLR效应蛋白抑制植物免疫分子机制也取得了显著进展。RXLR效应蛋白的研究有助于揭示致病疫霉与马铃薯互作分子机制,并进一步为马铃薯抗病育种工作提供新思路。主要概述了致病疫霉RXLR效应蛋白的相关研究进展,重点介绍了致病疫霉AVR基因的克隆、定位、变异及功能等方面的最新进展,同时对未来值得关注的研究方向进行了探讨。     

福建省部分地区马铃薯致病疫霉群体遗传多样性分析

致病疫霉(Phytophthora infestans)引起的晚疫病是马铃薯的一种毁灭性病害。有效控制马铃薯晚疫病需要明确致病疫霉的群体遗传结构特征。采用8对SSR引物对采自福建省福州、长乐、漳州2010年分离的95株马铃薯致病疫霉进行遗传多样性分析。结果共检测出21个等位基因和26个基因型。三个地点致病疫霉菌群体间的平均遗传分化系数FST为0.22,在8个位点中有5个位点的等位基因频率分布差异显著。三个群体的观测纯合度小于期望纯合度,观测杂合度大于期望杂合度,以无性生殖为主。结果表明福建群体的遗传多样性高,群体间的存在较高的遗传分化度。     

马铃薯晚疫病研究

马铃薯晚疫病是由疫霉(Phytophthora spp.)引起的严重的真菌病.马铃薯晚疫菌因导致马铃薯茎叶死亡和块茎腐烂而成为马铃薯疫灾中危害最大的病原菌,目前关于马铃薯晚疫病的研究方兴未艾.通过对马铃薯晚疫病的描述和菌的分离,分析了马铃薯的抗病机制以及基因工程方面研究进展,并提出建议,以便在育种方面参考.     

基于高通量测序的福建北部马铃薯晚疫病株根际土壤细菌群落分析

[背景]马铃薯晚疫病是一种由致病疫霉[Phytophthora infestans(Mont.)de Bary]引起的毁灭性病害,当环境条件适宜时,残留在土壤中的病原菌会侵染马铃薯植株导致病害的发生.[目的]明确健康马铃薯植株与发病植株的根际土壤细菌结构与多样性.[方法]采集马铃薯晚疫病发病地的健康植株根际土壤(M2J...     

美发现抗马铃薯晚疫病基因

Resource 2003年10卷9期4页报道：已知马铃薯晚疫病是由疫霉(Phytophthora spp．)引起的严重的真菌病。目前美国商业种植的全部马铃薯品种均高度易感马铃薯晚疫病。为了防治这种病害,最近美国威斯康星大学麦迪逊分校的植物病理学教授和美国农业部农业研究署的研究员John Helgeson及其同事已利用基因工程,将从墨西哥野生马铃薯(Solanum bulaocastanum)基因组中分离出来的抗马铃薯晚疫病的单基因,转移于栽培马铃薯。结果证实,这些转基因马铃薯可成功地抵抗多种疫霉的感染。     

一个马铃薯种质资源圃致病疫霉群体的分析

由致病疫霉Phytophthora infestans引起的晚疫病是马铃薯生产上最严重的病害之一,认识其群体结构特征,可为晚疫病防控策略的制定以及抗病品种的合理布局提供指导。对2009年采自宁夏一个种植有93个品种(品系)的马铃薯种质资源圃的致病疫霉进行了交配型、致病型和线粒体DNA单倍型分析,结果表明,116个致病疫霉菌株中存在A1、A2和自育型3种交配型,发生频率分别为24.1%、57.8%和18.1%,A2交配型为优势类型;对其中43个菌株的致病型进行测试,检测到两种致病类型:1.2.3.4.5.6.7.8.9.10.11和3.4.10,发生频率分别为95.3%和4.7%,可克服所有11个抗病基因的1.2.3.4.5.6.7.8.9.10.11类型占绝对优势;对62个菌株的线粒体DNA单倍型进行分析,检测到Ia和IIa两种类型,发生频率分别为74.2%和25.8%。综合表型和基因型数据分析发现,该马铃薯种质资源圃中致病疫霉群体致病型单一,但致病型毒力因子高度复合;线粒体DNA分析表明,该马铃薯种质资源圃引入了遗传背景较为复杂的致病疫霉"新"群体。     

致病疫霉在中国云南的马铃薯田间形成卵孢子*

由致病疫霉Phytophthora infestans (Mont.)de Bary引起的马铃薯和番茄晚疫病是世界性的作物病害,每年均造成巨大的经济损失和社会影响。致病疫霉是异宗配合的卵菌,有两个已知交配型A1和A2,两个相对交配型互作时可进行有性生殖产生卵孢子( Gallegly & Galindo,1958)。过去许多年一直认为致病疫霉在除墨西哥以外的国家中只存在A1交配型,通过产生孢子囊进行无性繁殖。近年来,由于致病疫霉新致病群体的产生以及全球范围的迁移和替代,A2交配型菌株先后在欧洲、美洲、亚洲和非洲的许多国家被发现。A1、A2两种交配型菌株的同时存在,增…     

尖孢镰刀菌全基因组测序及其致病相关基因分析

尖孢镰刀菌是导致三七根腐病的病原之一。本研究采用Illumina高通量测序技术对三七根腐病原菌(Fusarium oxysporum)的基因组扫描测序,并进行了基因组序列分析、基因功能注释和比较基因组学分析,从全基因组水平鉴定致病相关基因。扫描结果表明,基因组大小为48.12 Mb,G+C含量为51.5%,15 746个基因编码区(CDS),其中11 330个基因(71.95%)可以在COG数据库中得到其分类信息,编码有功能的蛋白6 022个。该序列已经提交GenBank数据库,登录号为SAMN09976373。进一步分析得到细胞壁降解相关基因45个,搜索数据库中F. oxysporum MAPK级联途径组分的基因序列,与酿酒酵母中MAPK级联途径进行比对并进行系统进化分析。研究结果对深入理解尖孢镰刀菌导致三七致病的分子机理,从而进一步有效控制病害的发生具有重要意义。     

马铃薯晚疫病防治的转基因策略

晚疫病是由致病疫霉菌(Phytophthora infestans)引起的病害,是限制马铃薯产业发展最严重的病害之一。采用传统育种和化学农药等方法防治马铃薯晚疫病虽然早有研究,但至今收效甚微。基因工程技术的兴起为防治马铃薯晚疫病提供了新的契机,并已取得了一定成效。但单基因抗性容易丧失、水平抗性应用难度大,要提高抗病基因的持久性,同时释放多个抗病基因,人为提高田间抗病基因的多态性是目前可选途径之一。对各种防治方法进行了综述,通过转基因技术创建抗病基因近等混合系是持久防治马铃薯晚疫病的首选可行方法,概述了其发展前景。     

中国部分地区马铃薯寄主上致病疫霉SSR基因型分析

利用两对SSR引物对两个基因座Pi4B和Pi4G进行了PCR扩增,测定了中国部分地区66个致病疫霉Phyophthora infestans(马铃薯晚疫病菌)菌株和2个参考菌株的SSR基因型,并对菌株的基因型进行了鉴定和命名.在被测定的66个致病疫霉菌株中,共产生了7种SSR基因型D-03,D-05,D-06,G-02,H-01,F-01和F-06,其中F-06为本研究新命名的基因型.F-01基因型菌株53个,占总菌株数目的80.3%,该基因型为中国致病疫霉的优势基因型.在对两个基因座Pi4B和Pi4G产生的等位基因统计分析发现基因座Pi4B产生的多样性比Pi4G高.对SSR数据揭示的河北、黑龙江和云南3个不同省份致病疫霉遗传多样性的比较发现,河北省和黑龙江省致病疫霉遗传多样性几乎相同,然而与云南省致病疫霉有较大的遗传差异.此外,发现致病疫霉SSR基因型与其对甲霜灵抗性无相关性.     

Effector genomics accelerates discovery and functional profiling of potato disease resistance and phytophthora infestans avirulence genes

Potato is the world's fourth largest food crop yet it continues to endure late blight, a devastating disease caused by the Irish famine pathogen Phytophthora infestans. Breeding broad-spectrum disease resistance (R) genes into potato (Solanum tuberosum) is the best strategy for genetically managing late blight but current approaches are slow and inefficient. We used a repertoire of effector genes predicted computationally from the P. infestans genome to accelerate the identification, functional characterization, and cloning of potentially broad-spectrum R genes. An initial set of 54 effectors containing a signal peptide and a RXLR motif was profiled for activation of innate immunity (avirulence or Avr activity) on wild Solanum species and tentative Avr candidates were identified. The RXLR effector family IpiO induced hypersensitive responses (HR) in S. stoloniferum, S. papita and the more distantly related S. bulbocastanum, the source of the R gene Rpi-blb1. Genetic studies with S. stoloniferum showed cosegregation of resistance to P. infestans and response to IpiO. Transient co-expression of IpiO with Rpi-blb1 in a heterologous Nicotiana benthamiana system identified IpiO as Avr-blb1. A candidate gene approach led to the rapid cloning of S. stoloniferum Rpi-sto1 and S. papita Rpi-pta1, which are functionally equivalent to Rpi-blb1. Our findings indicate that effector genomics enables discovery and functional profiling of late blight R genes and Avr genes at an unprecedented rate and promises to accelerate the engineering of late blight resistant potato varieties.     

Computational and comparative analyses of 150 full-length cDNA sequences from the oomycete plant pathogen Phytophthora infestans

Phytophthora infestans is a devastating phytopathogenic oomycete that causes late blight on tomato and potato. Recent genome sequencing efforts of P. infestans and other Phytophthora species are generating vast amounts of sequence data providing opportunities to unlock the complex nature of pathogenesis. However, accurate annotation of Phytophthora genomes will be a significant challenge. Most of the information about gene structure in these species was gathered from a handful of genes resulting in significant limitations for development of ab initio gene-calling programs. In this study, we collected a total of 150 bioinformatically determined near full-length cDNA (FLcDNA) sequences of P. infestans that were predicted to contain full open reading frame sequences. We performed detailed computational analyses of these FLcDNA sequences to obtain a snapshot of P. infestans gene structure, gauge the degree of sequence conservation between P. infestans genes and those of Phytophthora sojae and Phytophthora ramorum, and identify patterns of gene conservation between P. infestans and various eukaryotes, particularly fungi, for which genome-wide translated protein sequences are available. These analyses helped us to define the structural characteristics of P. infestans genes using a validated data set. We also determined the degree of sequence conservation within the genus Phytophthora and identified a set of fast evolving genes. Finally, we identified a set of genes that are shared between Phytophthora and fungal phytopathogens but absent in animal fungal pathogens. These results confirm that plant pathogenic oomycetes and fungi share virulence components, and suggest that eukaryotic microbial pathogens that share similar lifestyles also share a similar set of genes independently of their phylogenetic relatedness.     

Pathogen virulence of Phytophthora infestans: from gene to functional genomics

The oomycete, Phytophthora infestans, is one of the most important plant pathogens worldwide. Much of the pathogenic success of P. infestans, the potato late blight agent, relies on its ability to generate large amounts of sporangia from mycelia, which release zoospores that encyst and form infection structures. Until recently, little was known about the molecular basis of oomycete pathogenicity by the avirulence molecules that are perceived by host defenses. To understand the molecular mechanisms interplay in the pathogen and host interactions, knowledge of the genome structure was most important, which is available now after genome sequencing. The mechanism of biotrophic interaction between potato and P. infestans could be determined by understanding the effector biology of the pathogen, which is until now poorly understood. The recent availability of oomycete genome will help in understanding of the signal transduction pathways followed by apoplastic and cytoplasmic effectors for translocation into host cell. Finally based on genomics, novel strategies could be developed for effective management of the crop losses due to the late blight disease.     

Development of PCR primers from internal transcribed spacer region 2 for detection of Phytophthora species infecting potatoes.

We developed PCR primers and assay methods to detect and differentiate three Phytophthora species which infect potatoes and cause late blight (Phytophthora infestans) and pink rot (P. erythroseptica and P. nicotianae) diseases. Primers based on sequence analysis of internal transcribed spacer region 2 of ribosomal DNA produced PCR products of 456 bp (P. infestans), 136 bp (P. erythroseptica), and 455 bp (P. nicotianae) and were used to detect the pathogens in potato leaf (P. infestans) and tuber (P. infestans, P. erythroseptica, and P. nicotianae) tissue with a sensitivity of 1 to 10 pg of DNA. Leaf and tuber tissue were processed for PCR by a rapid NaOH method as well as a method based on the use of commercially available ion-exchange columns of P. infestans primers and the rapid NaOH extraction method were used to detect late blight in artificially and naturally infected tubers of potato cultivar Red LaSoda. In sampling studies, P. infestans was detected by PCR from artificially infected tubers at 4 days postinoculation, before any visible symptoms were present. The PCR assay and direct tissue extraction methods provide tools which may be used to detect Phytophthora pathogens in potato seedlots and storages and thus limit the transmission and spread of new, aggressive strains of P. infestans in U.S. potato-growing regions.     

Tracking historic migrations of the Irish potato famine pathogen,Phytophthora infestans

The plant pathogen Phytophthora infestans causes late blight, a devastating disease on potato that led to the Irish potato famine during 1845-1847. The disease is considered a reemerging problem and still causes major epidemics on both potato and tomato crops worldwide. Theories on the origin of the disease based on an examination of the genetic diversity and structure of P. infestans populations and use of historic specimens to understand modern day epidemics are discussed.     

Inducible Positive Mutant Screening System to Unveil the Signaling Pathway of Late Blight Resistance

Late blight is the most devastating potato disease and it also causes serious yield loss in tomato.Several disease resistance genes (R genes) to late blight have been cloned from potato in the past decade.However,the resistance mechanisms remain elusive.Tomato and potato belong to the botanical family Solanaceace and share remarkably conserved genome structure.Since tomato is a model system in genetic and plant pathology research,we used tomato to develop a powerful mutant screening system that will greatly facilitate the analysis of the signaling pathway of resistance to Phytophthora infestans.First we proved that the R3a transgenic tomatoes developed specific hypersensitive cell death response (HR) to P.infestans strains carrying the corresponding avirulence gene Avr3a,indicating that the signaling pathway from the R3a-Avr3a recognition to HR is conserved between potato and tomato.Second,we generated transgenic tomatoes carrying both R3a and Avr3a genes,with the latter under the control of a glucocorticiod-inducible promoter.Dexamethasone induced expression of Avr3a and resulted in localized HR.This versatile system can be used to construct a mutant library to screen surviving mutants whose resistance signal transduction was interrupted,providing the basis to identify key genes involved in the resistance to late blight in Solanaceae.     

Families of short interspersed elements in the genome of the oomycete plant pathogen, Phytophthora infestans

The first known families of tRNA-related short interspersed elements (SINEs) in the oomycetes were identified by exploiting the genomic DNA sequence resources for the potato late blight pathogen, Phytophthora infestans. Fifteen families of tRNA-related SINEs, as well as predicted tRNAs, and other possible RNA polymerase III-transcribed sequences were identified. The size of individual elements ranges from 101 to 392 bp, representing sequences present from low (1) to highly abundant (over 2000) copy number in the P. infestans genome, based on quantitative PCR analysis. Putative short direct repeat sequences (6-14 bp) flanking the elements were also identified for eight of the SINEs. Predicted SINEs were named in a series prefixed infSINE (for infestans-SINE). Two SINEs were apparently present as multimers of tRNA-related units; four copies of a related unit for infSINEr, and two unrelated units for infSINEz. Two SINEs, infSINEh and infSINEi, were typically located within 400 bp of each other. These were also the only two elements identified as being actively transcribed in the mycelial stage of P. infestans by RT-PCR. It is possible that infSINEh and infSINEi represent active retrotransposons in P. infestans. Based on the quantitative PCR estimates of copy number for all of the elements identified, tRNA-related SINEs were estimated to comprise 0.3% of the 250 Mb P. infestans genome. InfSINE-related sequences were found to occur in species throughout the genus Phytophthora. However, seven elements were shown to be exclusive to P. infestans.     

Resistance to Phytophthora infestans in somatic hybrids of Solanum nigrum L. and diploid potato

In breeding for resistance to late blight, ( Phytophthora infestans Mont. de Bary), an economically important disease affecting potatoes, the search for new sources of durable resistance includes the non-host wild Solanum species. The aim of this work was to evaluate the resistance to P. infestans in the somatic hybrids between S. nigrum L. and diploid potato clone ZEL-1136. Sixteen somatic hybrids, their fusion parents, and three standard potato cultivars were screened for resistance to P. infestans in two types of tests-on whole plants and detached leaves-with two highly aggressive and virulent isolates of P. infestans, US8 and MP322. In the whole plant assay, the foliage of the somatic hybrids showed no symptoms of infection, while the foliage of the potato fusion parent and the standard cultivars was infected with P. infestans. In the detached leaflet assay, the breaking-down of resistance of the S. nigrum L. parent and the variable response of individual hybrid clones were noted. Nine S. nigrum L. (+) ZEL-1136 hybrids showed a resistance that was significantly higher than that of S. nigrum, while six clones expressed a resistance to P. infestans similar to that of S. nigrum. The results confirm the effective transfer of late blight resistance of S. nigrum into its somatic hybrids with potato.     

The R1 gene for potato resistance to late blight (Phytophthora infestans) belongs to the leucine zipper/NBS/LRR class of plant resistance genes

Late blight caused by the oomycete Phytophthora infestans is the most destructive disease in potato cultivation worldwide. New, more virulent P. infestans strains have evolved which overcome the genetic resistance that has been introgressed by conventional breeding from wild potato species into commercial varieties. R genes (for single-gene resistance) and genes for quantitative resistance to late blight are present in the germplasm of wild and cultivated potato. The molecular basis of single-gene and quantitative resistance to late blight is unknown. We have cloned R1, the first gene for resistance to late blight, by combining positional cloning with a candidate gene approach. The R1 gene is member of a gene family. It encodes a protein of 1293 amino acids with a molecular mass of 149.4 kDa. The R1 gene belongs to the class of plant genes for pathogen resistance that have a leucine zipper motif, a putative nucleotide binding domain and a leucine-rich repeat domain. The most closely related plant resistance gene (36% identity) is the Prf gene for resistance to Pseudomonas syringae of tomato. R1 is located within a hot spot for pathogen resistance on potato chromosome V. In comparison to the susceptibility allele, the resistance allele at the R1 locus represents a large insertion of a functional R gene.