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Arbuscular Mycorrhizal Symbiosis Affects Plant Immunity to Viral Infection and Accumulation.
Hao, Z, Xie, W, Chen, B
Viruses. 2019;(6)
Abstract
Arbuscular mycorrhizal (AM) fungi, as root symbionts of most terrestrial plants, improve plant growth and fitness. In addition to the improved plant nutritional status, the physiological changes that trigger metabolic changes in the root via AM fungi can also increase the host ability to overcome biotic and abiotic stresses. Plant viruses are one of the important limiting factors for the commercial cultivation of various crops. The effect of AM fungi on viral infection is variable, and considerable attention is focused on shoot virus infection. This review provides an overview of the potential of AM fungi as bioprotection agents against viral diseases and emphasizes the complex nature of plant-fungus-virus interactions. Several mechanisms, including modulated plant tolerance, manipulation of induced systemic resistance (ISR), and altered vector pressure are involved in such interactions. We propose that using "omics" tools will provide detailed insights into the complex mechanisms underlying mycorrhizal-mediated plant immunity.
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2.
Horizontal and endosymbiotic gene transfer in early plastid evolution.
Ponce-Toledo, RI, López-García, P, Moreira, D
The New phytologist. 2019;(2):618-624
Abstract
Plastids evolved from a cyanobacterium that was engulfed by a heterotrophic eukaryotic host and became a stable organelle. Some of the resulting eukaryotic algae entered into a number of secondary endosymbioses with diverse eukaryotic hosts. These events had major consequences on the evolution and diversification of life on Earth. Although almost all plastid diversity derives from a single endosymbiotic event, the analysis of nuclear genomes of plastid-bearing lineages has revealed a mosaic origin of plastid-related genes. In addition to cyanobacterial genes, plastids recruited for their functioning eukaryotic proteins encoded by the host nucleus and also bacterial proteins of noncyanobacterial origin. Therefore, plastid proteins and plastid-localised metabolic pathways evolved by tinkering and using gene toolkits from different sources. This mixed heritage seems especially complex in secondary algae containing green plastids, the acquisition of which appears to have been facilitated by many previous acquisitions of red algal genes (the 'red carpet hypothesis').
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3.
The origin and evolution of mycorrhizal symbioses: from palaeomycology to phylogenomics.
Strullu-Derrien, C, Selosse, MA, Kenrick, P, Martin, FM
The New phytologist. 2018;(4):1012-1030
Abstract
Contents Summary 1012 I. Introduction 1013 II. The mycorrhizal symbiosis at the dawn and rise of the land flora 1014 III. From early land plants to early trees: the origin of roots and true mycorrhizas 1016 IV. The diversification of the AM symbiosis 1019 V. The ECM symbiosis 1021 VI. The recently evolved ericoid and orchid mycorrhizas 1023 VII. Limits of paleontological vs genetic approaches and perspectives 1023 Acknowledgements 1025 References 1025 SUMMARY The ability of fungi to form mycorrhizas with plants is one of the most remarkable and enduring adaptations to life on land. The occurrence of mycorrhizas is now well established in c. 85% of extant plants, yet the geological record of these associations is sparse. Fossils preserved under exceptional conditions provide tantalizing glimpses into the evolutionary history of mycorrhizas, showing the extent of their occurrence and aspects of their evolution in extinct plants. The fossil record has important roles to play in establishing a chronology of when key fungal associations evolved and in understanding their importance in ecosystems through time. Together with calibrated phylogenetic trees, these approaches extend our understanding of when and how groups evolved in the context of major environmental change on a global scale. Phylogenomics furthers this understanding into the evolution of different types of mycorrhizal associations, and genomic studies of both plants and fungi are shedding light on how the complex set of symbiotic traits evolved. Here we present a review of the main phases of the evolution of mycorrhizal interactions from palaeontological, phylogenetic and genomic perspectives, with the aim of highlighting the potential of fossil material and a geological perspective in a cross-disciplinary approach.
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4.
Nitrate-mediated control of root nodule symbiosis.
Nishida, H, Suzaki, T
Current opinion in plant biology. 2018;:129-136
Abstract
Nitrogen is an indispensable inorganic nutrient that is required by plants throughout their life. Root nodule symbiosis (RNS) is an important strategy mainly adopted by legumes to enhance nitrogen acquisition, where several key processes required for the establishment of the symbiosis, are pleiotropically controlled by nitrate availability in soil. Although the autoregulation of nodulation (AON), a systemic long-range signaling, has been suggested to be implicated in nitrate-induced control of RNS, AON alone is insufficient to fully explain the pleiotropic regulation that is induced by nitrate. A recent elucidation of the function of a NIN-LIKE PROTEIN transcription factor has provided greater insights into the genetic mechanisms underlying nitrate-induced control of RNS in varying nitrate environments.
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5.
Unity in diversity: structural and functional insights into the ancient partnerships between plants and fungi.
Field, KJ, Pressel, S
The New phytologist. 2018;(4):996-1011
Abstract
Contents Summary 996 I. Introduction 996 II. An ancient, and diverse, symbiosis 998 III. Structural diversity in ancient plant-fungal partnerships 1000 IV. Mycorrhizal unity in host plant nutrition 1002 V. Plant-to-fungus carbon transfer 1003 VI. From individuals to networks 1003 VII. Diverse responses of mycorrhizal functioning to dynamic environments 1006 VIII. Summary of future research direction 1007 Acknowledgements 1006 References 1006 SUMMARY Mycorrhizal symbiosis is an ancient and widespread mutualism between plants and fungi that facilitated plant terrestrialisation > 500 million years ago, with key roles in ecosystem functioning at multiple scales. Central to the symbiosis is the bidirectional exchange of plant-fixed carbon for fungal-acquired nutrients. Within this unifying role of mycorrhizas, considerable diversity in structure and function reflects the diversity of the partners involved. Early diverging plants form mutualisms not only with arbuscular mycorrhizal Glomeromycotina fungi, but also with poorly characterised Mucoromycotina, which may also colonise the roots of 'higher' plants as fine root endophytes. Functional diversity in these symbioses depends on both fungal and plant life histories and is influenced by the environment. Recent studies have highlighted the roles of lipids/fatty acids in plant-to-fungus carbon transport and potential contributions of Glomeromycotina fungi to plant nitrogen nutrition. Together with emerging appreciation of mycorrhizal networks as multi-species resource-sharing systems, these insights are broadening our views on mycorrhizas and their roles in nutrient cycling. It is crucial that the diverse array of biotic and abiotic factors that together shape the dynamics of carbon-for-nutrient exchange between plants and fungi are integrated, in addition to embracing the unfolding and potentially key role of Mucoromycotina fungi in these processes.
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6.
Rhizobia: from saprophytes to endosymbionts.
Poole, P, Ramachandran, V, Terpolilli, J
Nature reviews. Microbiology. 2018;(5):291-303
Abstract
Rhizobia are some of the best-studied plant microbiota. These oligotrophic Alphaproteobacteria or Betaproteobacteria form symbioses with their legume hosts. Rhizobia must exist in soil and compete with other members of the microbiota before infecting legumes and forming N2-fixing bacteroids. These dramatic lifestyle and developmental changes are underpinned by large genomes and even more complex pan-genomes, which encompass the whole population and are subject to rapid genetic exchange. The ability to respond to plant signals and chemoattractants and to colonize nutrient-rich roots are crucial for the competitive success of these bacteria. The availability of a large body of genomic, physiological, biochemical and ecological studies makes rhizobia unique models for investigating community interactions and plant colonization.
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7.
Cross-kingdom lipid transfer in arbuscular mycorrhiza symbiosis and beyond.
Keymer, A, Gutjahr, C
Current opinion in plant biology. 2018;:137-144
Abstract
Arbuscular mycorrhiza (AM) is a widespread symbiosis between most land plants and fungi of the Glomeromycotina, which has existed for more than 400million years. AM fungi (AMF) improve plant nutrition with mineral nutrients and conversely, their growth and development is fueled by organic carbon supplied from their host. Recent studies demonstrated independently and with different experimental approaches that lipids are transferred from plants to fungi in addition to sugars, and that AMF are dependent on this lipid supply because they lack genes encoding fatty acid synthase I subunits. Dependence on host lipids or lipid parasitism occur in a range of interorganismic associations with participants from almost all kingdoms. Thus, these phenomena seem rather common in mutualistic and parasitic interactions.
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8.
The impact of domestication and crop improvement on arbuscular mycorrhizal symbiosis in cereals: insights from genetics and genomics.
Sawers, RJH, Ramírez-Flores, MR, Olalde-Portugal, V, Paszkowski, U
The New phytologist. 2018;(4):1135-1140
Abstract
Contents Summary 1135 I. Introduction 1135 II. Recruitment of plant metabolites and hormones as signals in AM symbiosis 1136 III. Phytohormones are regulators of AM symbiosis and targets of plant breeding 1137 IV. Variation in host response to AM symbiosis 1137 V. Outlook 1137 Acknowledgements 1139 References 1139 SUMMARY Cereals (rice, maize, wheat, sorghum and the millets) provide over 50% of the world's caloric intake, a value that rises to > 80% in developing countries. Since domestication, cereals have been under artificial selection, largely directed towards higher yield. Throughout this process, cereals have maintained their capacity to interact with arbuscular mycorrhizal (AM) fungi, beneficial symbionts that associate with the roots of most terrestrial plants. It has been hypothesized that the shift from the wild to cultivation, and above all the last c. 50 years of intensive breeding for high-input farming systems, has reduced the capacity of the major cereal crops to gain full benefit from AM interactions. Recent studies have shed further light on the molecular basis of establishment and functioning of AM symbiosis in cereals, providing insight into where the breeding process might have had an impact. Classic phytohormones, targets of artificial selection during the generation of Green Revolution semi-dwarf varieties, have emerged as important regulators of AM symbiosis. Although there is still much to be learnt about the mechanistic basis of variation in symbiotic outcome, these advances are providing an insight into the role of arbuscular mycorrhiza in agronomic systems.
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9.
Causal Relationship between Diet-Induced Gut Microbiota Changes and Diabetes: A Novel Strategy to Transplant Faecalibacterium prausnitzii in Preventing Diabetes.
Ganesan, K, Chung, SK, Vanamala, J, Xu, B
International journal of molecular sciences. 2018;(12)
Abstract
The incidence of metabolic disorders, including diabetes, has elevated exponentially during the last decades and enhanced the risk of a variety of complications, such as diabetes and cardiovascular diseases. In the present review, we have highlighted the new insights on the complex relationships between diet-induced modulation of gut microbiota and metabolic disorders, including diabetes. Literature from various library databases and electronic searches (ScienceDirect, PubMed, and Google Scholar) were randomly collected. There exists a complex relationship between diet and gut microbiota, which alters the energy balance, health impacts, and autoimmunity, further causes inflammation and metabolic dysfunction, including diabetes. Faecalibacterium prausnitzii is a butyrate-producing bacterium, which plays a vital role in diabetes. Transplantation of F. prausnitzii has been used as an intervention strategy to treat dysbiosis of the gut's microbial community that is linked to the inflammation, which precedes autoimmune disease and diabetes. The review focuses on literature that highlights the benefits of the microbiota especially, the abundant of F. prausnitzii in protecting the gut microbiota pattern and its therapeutic potential against inflammation and diabetes.
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10.
Partner communication and role of nutrients in the arbuscular mycorrhizal symbiosis.
Lanfranco, L, Fiorilli, V, Gutjahr, C
The New phytologist. 2018;(4):1031-1046
Abstract
Contents Summary 1031 I. Introduction 1031 II. Interkingdom communication enabling symbiosis 1032 III. Nutritional and regulatory roles for key metabolites in the AM symbiosis 1035 IV. The plant-fungus genotype combination determines the outcome of the symbiosis 1039 V. Perspectives 1039 Acknowledgements 1041 References 1041 SUMMARY The evolutionary and ecological success of the arbuscular mycorrhizal (AM) symbiosis relies on an efficient and multifactorial communication system for partner recognition, and on a fine-tuned and reciprocal metabolic regulation of each symbiont to reach an optimal functional integration. Besides strigolactones, N-acetylglucosamine-derivatives released by the plant were recently suggested to trigger fungal reprogramming at the pre-contact stage. Remarkably, N-acetylglucosamine-based diffusible molecules also are symbiotic signals produced by AM fungi (AMF) and clues on the mechanisms of their perception by the plant are emerging. AMF genomes and transcriptomes contain a battery of putative effector genes that may have conserved and AMF- or host plant-specific functions. Nutrient exchange is the key feature of AM symbiosis. A mechanism of phosphate transport inside fungal hyphae has been suggested, and first insights into the regulatory mechanisms of root colonization in accordance with nutrient transfer and status were obtained. The recent discovery of the dependency of AMF on fatty acid transfer from the host has offered a convincing explanation for their obligate biotrophism. Novel studies highlighted the importance of plant and fungal genotypes for the outcome of the symbiosis. These findings open new perspectives for fundamental research and application of AMF in agriculture.