植物抗细菌病害基因工程研究进展和展望

综述了利用基因工程提高植物对细菌病害抗性的各种方法,包括利用非植物抗菌蛋白,抑制细菌的致病或毒性因子,增强植物本身的抗病能力和人工诱导侵染点细胞程序化坏死。这些方法的成功都与抗菌化合物的作用机制及植物和病原细菌之间的相互作用的分子生物学的研究密切相关,还展望了这些方法的应用前景。     

植物相关细菌中Ⅵ型分泌系统的功能研究进展北大核心

型分泌系统(typeⅥsecretion system,T6SS)是一种强大的细菌分子武器,它通过将效应蛋白注入原核或真核细胞而介导细菌间竞争并影响宿主的生命活动。T6SS广泛分布于革兰氏阴性菌中,主要存在于变形菌门(Proteobacteria)。尽管T6SS的研究大多集中在动物相关细菌上,但它在植物相关细菌中的作用不能被忽视。本文对植物相关细菌的T6SS进行了较为详细的介绍,主要从T6SS的发现、T6SS在植物相关细菌间竞争中的作用、在细菌与植物互作中的作用以及在植物生物防治中的作用等4个方面综述了最新的研究成果,旨在为今后更好地研究植物相关细菌T6SS的生物学功能及其应用提供指导。     

植物内生细菌的研究

植物内生细菌是能够定殖在植物细胞间隙或细胞内,并与寄主植物建立和谐联合关系的一类微生物I’］。自本世纪初开始,人们不断地从植物的根、叶、甚至茎和种子上分离并鉴定出多种微生物,但其在寄主植物中的生物学作用却未能引起研究者的重视。近年来,由于一些研究结果表明内生细菌能够作为外源基因的载体,又具有植物保护剂的功能,可以产生植物促生物质或可作为联合固氮菌剂,由此有关内生细菌的研究才引起植物学家和微生物学家的兴趣。l植物内生细菌的研究现状有关植物内生细菌的研究主要涉及两方面的内容：（l）生态学研究：内生细菌…     

细菌信号分子N-酰基高丝氨酸内酯调控植物抗病反应的研究进展

N-酰基高丝氨酸内酯(AHLs)在生物信息交流中发挥了重要作用,为革兰氏阴性细菌种内和种间的相互作用提供了化学基础并参与细菌多种生理行为的调控。不仅是细菌,植物同样可以感知AHLs,并作出反应。综述近几年来AHLs调控植物抗病反应的研究进展,有助于探究AHLs对寄主植物的影响途径和机理,旨为在农业上的应用奠定理论基础。     

植物识别子与病原细菌识别子间的相互作用

本文介绍了不同的植物-病原细菌相互作用体系中植物识别子和病原细菌识别子的种类、性质,评述了两类识别子之间相互作用的分子学、细胞学和生理生化学及其意义。     

N-酰基高丝氨酸内酯调控植物生长发育的研究进展

植物与细菌之间存在着复杂的相互作用关系。N-酰基高丝氨酸内酯（AHLs）是革兰氏阴性细菌进行胞间通讯的信号分子,也是介导植物与细菌互作的重要信号分子,在调控植物生长发育方面起着重要作用。本文对近年来的相关研究进展作一综述,这将有助于全面了解植物与细菌间的信息交流机制,并对实际农业生产具有指导意义。     

抗植物细菌病害基因工程的研究进展

综述了利用基因工程技术提高植物抵抗细菌病害能力的研究进展。植物抗细菌病害基因工程的方法包括：阻断病原细菌的致病途径,强化植物抗病反应及其信号转导途径,导入植物防御基因,导入非植物源抗菌蛋白的编码基因,利用细胞调亡反应控制病害的发生。随着基因组学和功能基因组学的发展,和对植物与病原细菌之间相互作用更深入的了解,植物抗细菌病害基因工程所面临的问题会逐步得到解决,因此利用植物基因工程技术培育抗病品种将具有广阔的应用前景。     

植物内生细菌修复重金属污染土壤作用机制研究进展

内生细菌生活在植物组织内部,长期以来与宿主植物形成了紧密的共生关系。内生细菌在重金属吸收、耐受和解毒方面具有优良的特性,为修复重金属污染土壤提供了有效的新方案。综述了内生细菌强化植物修复重金属污染土壤的作用机制,包括内生细菌通过产生植物生长调节激素,分泌ACC脱氨酶和几丁质酶等,促进宿主植物在重金属胁迫条件下的生长;通过改变重金属的生物有效性/毒性,减轻植物重金属毒害;通过与植物形成联合修复体,加强植物抗重金属毒性的能力。分析了近几年超富集植物内生细菌多样性及其影响因素,探讨了联合修复过程中影响内生细菌强化修复效果的主要因素,包括内生细菌的来源、活性和环境胁迫等各种生物因素和非生物因素,并对内生细菌与植物联合修复的研究方向进行展望,涉及内生细菌自身存活原因和如何耐受重金属的机制研究,植物内生细菌的行为动力学和代谢,以及内生细菌、植物及土壤之间的生态互作效应等,以期推动内生细菌大规模应用于植物修复重金属污染土壤。     

植物内生细菌对植物健康的作用

植物内生菌是一个多样性十分丰富的微生物类群,存在于没有外在感染症状的健康植物组织内,并与宿主植物协同进化.随着研究领域的不断拓宽和研究方法的不断更新,植物内生菌与植物健康的关系以及应用逐渐成为研究热点.本文主要综述了内生细菌的多样性、进入植物组织内的机制以及内生细菌的主要功能及应用,提出了现阶段内生菌研究存在的问题,并展望了内生菌研究的前景.     

植物内生细菌在植物修复重金属污染土壤中的应用

土壤重金属污染是威胁人群健康和经济可持续发展的重要环境问题。植物修复具有经济、环保等特点,已成为治理重金属污染土壤的重要技术。如何提高植物对重金属的抗性、促进植物生长是影响植物修复效率的关键之一。内生菌群-植物共生关系在此方面具有独特优势。其中,植物内生细菌可改善植物营养、降低植物病菌感染、影响酶活性,以及分泌激素、含铁载体和有机配位体等,进而提高超积累植物对重金属的吸收作用。本文综述了近年来国内外关于抗重金属植物内生细菌筛选与应用的研究进展,分析了内生细菌促进植物生长、增强植物对重金属抗性、促进重金属向茎叶转移的机理,阐述了植物内生细菌在重金属污染土壤修复中的应用前景与研究重点。     

Aerobic methylotroph bacteria as phytosymbionts]

This paper deals with the physiological, biochemical, and molecular genetic aspects of the interaction of aerobic methylotrophic bacteria with plants by means of phytohormones (such as cytokinins and auxins) and other physiologically active substances (vitamins, exopolysaccharides, bioprotectants). The state of the art and the prospects of research in the field of bacteria-plant interactions and the application of aerobic methylotrophs in plant biotechnology is discussed.     

Olive orchard microbiome: characterisation of bacterial communities in soil-plant compartments and their comparison between sustainable and conventional soil management systems

ABSTRACT

Background

Beneficial bacteria-plant interactions play an important role in agriculture, positively affecting plant status and improving product quality. Bacterial endophytes contribute to host plant protection and survival.     

Population genetics of rhizobia: construction and analysis of an "Infection and Release" model

A mathematical model is created to assess the inputs of sym gene transfer of in planta multiplication and of interstrain competition into dynamics of the rhizobia populations. Their microevolution is presented as a series of the "infection and release" cycles; each cycle includes transfer of sym genes from virulent initial symbionts to avirulent local bacteria yielding the virulent novel symbionts; competition between initial symbionts and novel symbionts for the host nodulation; multiplication of initial symbionts and novel symbionts in planta and their release into soil; competition between the released novel symbionts and resident local bacteria for ex planta survival. A recurrent equation is created to determine the number of novel symbionts at each cycle of evolution of the closed bacteria-plant system. Its analysis demonstrates that under certain, really allowable values of the introduced parameters two major effects may occur: (a) rapid multiplication of novel symbionts arisen from sym gene transfer; and (b) increase of frequency of rare local bacteria genotypes after acquisition of virulence. Multiplication of very rare strains (p<10(-19)) in the plant-associated bacteria population is possible at certain parameters of the system. Variation of the sizes of bacteria populations and of the parameters for interstrain competition may influence the evolutionary rate of the bacteria population. The "infection and release" model represents a selective mechanism which may be responsible for a high taxonomic diversity of rhizobia and for a panmictic structure of their populations.     

Collagen-Like Proteins (ClpA,ClpB, ClpC,and ClpD) Are Required for Biofilm Formation and Adhesion to Plant Roots by Bacillus amyloliquefaciens FZB42

The genes of collagen-like proteins (CLPs) have been identified in a broad range of bacteria, including some human pathogens. They are important for biofilm formation and bacterial adhesion to host cells in some human pathogenic bacteria, including several Bacillus spp. strains. Interestingly, some bacterial CLP-encoding genes (clps) have also been found in non-human pathogenic strains such as B. cereus and B. amyloliquefaciens, which are types of plant-growth promoting rhizobacteria (PGPR). In this study, we investigated a putative cluster of clps in B. amyloliquefaciens strain FZB42 and a collagen-related structural motif containing glycine-X-threonine repeats was found in the genes RBAM_007740, RBAM_007750, RBAM_007760, and RBAM_007770. Interestingly, biofilm formation was disrupted when these genes were inactivated separately. Scanning electron microscopy and hydrophobicity value detection were used to assess the bacterial cell shape morphology and cell surface architecture of clps mutant cells. The results showed that the CLPs appeared to have roles in bacterial autoaggregation, as well as adherence to the surface of abiotic materials and the roots of Arabidopsis thaliana. Thus, we suggest that the CLPs located in the outer layer of the bacterial cell (including the cell wall, outer membrane, flagella, or other associated structures) play important roles in biofilm formation and bacteria-plant interactions. This is the first study to analyze the function of a collagen-like motif-containing protein in a PGPR bacterium. Knocking out each clp gene produced distinctive morphological phenotypes, which demonstrated that each product may play specific roles in biofilm formation. Our in silico analysis suggested that these four tandemly ranked genes might not belong to an operon, but further studies are required at the molecular level to test this hypothesis. These results provide insights into the functions of clps during interactions between bacteria and plants.     

Substrate and Target Sequence Length Influence RecTEPsy Recombineering Efficiency in Pseudomonas syringae

We are developing a new recombineering system to assist experimental manipulation of the Pseudomonas syringae genome. P. syringae is a globally dispersed plant pathogen and an important model species used to study the molecular biology of bacteria-plant interactions. We previously identified orthologs of the lambda Red bet/exo and Rac recET genes in P. syringae and confirmed that they function in recombineering using ssDNA and dsDNA substrates. Here we investigate the properties of dsDNA substrates more closely to determine how they influence recombineering efficiency. We find that the length of flanking homologies and length of the sequences being inserted or deleted have a large effect on RecTE_Psy mediated recombination efficiency. These results provide information about the design elements that should be considered when using recombineering.     

Identification of genes differentially expressed during interaction of resistant and susceptible apple cultivars (Malus × domestica) with Erwinia amylovora

Background  

The necrogenic enterobacterium, Erwinia amylovora is the causal agent of the fire blight (FB) disease in many Rosaceaespecies, including apple and pear. During the infection process, the bacteria induce an oxidative stress response with kinetics similar to those induced in an incompatible bacteria-plant interaction. No resistance mechanism to E. amylovora in host plants has yet been characterized, recent work has identified some molecular events which occur in resistant and/or susceptible host interaction with E. amylovora: In order to understand the mechanisms that characterize responses to FB, differentially expressed genes were identified by cDNA-AFLP analysis in resistant and susceptible apple genotypes after inoculation with E. amylovora.     

Phylogenetic analysis of a gene cluster encoding an additional, rhizobial-like type III secretion system that is narrowly distributed among Pseudomonas syringae strains

ABSTRACT: BACKGROUND: The central role of Type III secretion systems (T3SS) in bacteria-plant interactions is well established, yet unexpected findings are being uncovered through bacterial genome sequencing. Some Pseudomonas syringae strains possess an uncharacterized cluster of genes encoding putative components of a second T3SS (T3SS-2) in addition to the well characterized Hrc1 T3SS which is associated with disease lesions in host plants and with the triggering of hypersensitive response in non-host plants. The aim of this study is to perform an in silico analysis of T3SS-2, and to compare it with other known T3SSs. RESULTS: Based on phylogenetic analysis and gene organization comparisons, the T3SS-2 cluster of the P. syringae pv. phaseolicola strain is grouped with a second T3SS found in the pNGR234b plasmid of Rhizobium sp. These additional T3SS gene clusters define a subgroup within the Rhizobium T3SS family. Although, T3SS-2 is not distributed as widely as the Hrc1 T3SS in P. syringae strains, it was found to be constitutively expressed in P. syringae pv phaseolicola through RT-PCR experiments. CONCLUSIONS: The relatedness of the P. syringae T3SS-2 to a second T3SS from the pNGR234b plasmid of Rhizobium sp., member of subgroup II of the rhizobial T3SS family, indicates common ancestry and/or possible horizontal transfer events between these species. Functional analysis and genome sequencing of more rhizobia and P. syringae pathovars may shed light into why these bacteria maintain a second T3SS gene cluster in their genome.     

Interactions between Diatoms and Bacteria

Summary: Diatoms and bacteria have cooccurred in common habitats for hundreds of millions of years, thus fostering specific associations and interactions with global biogeochemical consequences. Diatoms are responsible for one-fifth of the photosynthesis on Earth, while bacteria remineralize a large portion of this fixed carbon in the oceans. Through their coexistence, diatoms and bacteria cycle nutrients between oxidized and reduced states, impacting bioavailability and ultimately feeding higher trophic levels. Here we present an overview of how diatoms and bacteria interact and the implications of these interactions. We emphasize that heterotrophic bacteria in the oceans that are consistently associated with diatoms are confined to two phyla. These consistent bacterial associations result from encounter mechanisms that occur within a microscale environment surrounding a diatom cell. We review signaling mechanisms that occur in this microenvironment to pave the way for specific interactions. Finally, we discuss known interactions between diatoms and bacteria and exciting new directions and research opportunities in this field. Throughout the review, we emphasize new technological advances that will help in the discovery of new interactions. Deciphering the languages of diatoms and bacteria and how they interact will inform our understanding of the role these organisms have in shaping the ocean and how these interactions may change in future oceans.