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1.
Nonproteinaceous effectors: the terra incognita of plant-fungal interactions.
Collemare, J, O'Connell, R, Lebrun, MH
The New phytologist. 2019;(2):590-596
Abstract
Molecular plant-fungal interaction studies have mainly focused on small secreted protein effectors. However, accumulating evidence shows that numerous fungal secondary metabolites are produced at all stages of plant colonization, especially during early asymptomatic/biotrophic phases. The discovery of fungal small RNAs targeting plant transcripts has expanded the fungal repertoire of nonproteinaceous effectors even further. The challenge now is to develop specific functional methods to fully understand the biological roles of these effectors. Studies on fungal extracellular vesicles are also needed because they could be the universal carriers of all kinds of fungal effectors. With this review, we aim to stimulate the nonproteinaceous effector research field to move from descriptive to functional studies, which should bring a paradigm shift in plant-fungal interactions.
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2.
Non-heme iron enzyme-catalyzed complex transformations: Endoperoxidation, cyclopropanation, orthoester, oxidative C-C and C-S bond formation reactions in natural product biosynthesis.
Song, H, Naowarojna, N, Cheng, R, Lopez, J, Liu, P
Advances in protein chemistry and structural biology. 2019;:1-61
Abstract
Non-heme iron enzymes catalyze a wide range of chemical transformations, serving as one of the key types of tailoring enzymes in the biosynthesis of natural products. Hydroxylation reaction is the most common type of reactions catalyzed by these enzymes and hydroxylation reactions have been extensively investigated mechanistically. However, the mechanistic details for other types of transformations remain largely unknown or unexplored. In this paper, we present some of the most recently discovered transformations, including endoperoxidation, orthoester formation, cyclopropanation, oxidative C-C and C-S bond formation reactions. In addition, many of them are multi-functional enzymes, which further complicate their mechanistic investigations. In this work, we summarize their biosynthetic pathways, with special emphasis on the mechanistic details available for these newly discovered enzymes.
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3.
New insights on yeast and filamentous fungus adhesion in a natural co-immobilization system: proposed advances and applications in wine industry.
Ogawa, M, Bisson, LF, García-Martínez, T, Mauricio, JC, Moreno-García, J
Applied microbiology and biotechnology. 2019;(12):4723-4731
Abstract
Fungi possess extraordinary strength in attachment to biotic and abiotic surfaces. This review focuses on adhesion mechanisms of yeast and filamentous fungi and the proposed combination of the adhesive forces of both organisms in an immobilization system called yeast biocapsules, whereby Saccharomyces cerevisiae cells are attached to the hyphae of Penicillium chrysogenum. The natural adherent properties of each organism, one multicellular and another unicellular, allow yeast to be fixated securely on the filamentous fungi and complete alcoholic fermentation. Following alcoholic fermentation, the hyphae become an inert support for yeast cells while maintaining shape and integrity. Biocapsules have been used successfully in both wine and bioethanol production. Investigation of the potential genes involved in fungal-yeast fusion suggests that natural hydrophobic interactions of both organisms play a major role. Analysis of the possible mechanisms involved in fungus and yeast adhesion, future perspectives on improving yeast immobilization, and proposed applications of the biocapsules are explored.
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4.
Ectomycorrhizal symbiosis helps plants to challenge salt stress conditions.
Guerrero-Galán, C, Calvo-Polanco, M, Zimmermann, SD
Mycorrhiza. 2019;(4):291-301
Abstract
Soil salinity is an environmental condition that is currently increasing worldwide. Plant growth under salinity induces osmotic stress and ion toxicity impairing root water and nutrient absorption, but the association with beneficial soil microorganisms has been linked to an improved adaptation to this constraint. The ectomycorrhizal (ECM) symbiosis has been proposed as a key factor for a better tolerance of woody species to salt stress, thanks to the reduction of sodium (Na+) uptake towards photosynthetic organs. Although no precise mechanisms for this enhanced plant salt tolerance have been described yet, in this review, we summarize the knowledge accumulated so far on the role of ECM symbiosis. Moreover, we propose several strategies by which ECM fungi might help plants, including restriction of Na+ entrance into plant tissues and improvement of mineral nutrition and water balances. This positive effect of ECM fungi has been proven in field assays and the results obtained point to a promising application in forestry cultures and reforestation.
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5.
Production and extraction of carotenoids produced by microorganisms.
Mussagy, CU, Winterburn, J, Santos-Ebinuma, VC, Pereira, JFB
Applied microbiology and biotechnology. 2019;(3):1095-1114
Abstract
Carotenoids are a group of isoprenoid pigments naturally synthesized by plants and microorganisms, which are applied industrially in food, cosmetic, and pharmaceutical product formulations. In addition to their use as coloring agents, carotenoids have been proposed as health additives, being able to prevent cancer, macular degradation, and cataracts. Moreover, carotenoids may also protect cells against oxidative damage, acting as an antioxidant agent. Considering the interest in greener and sustainable industrial processing, the search for natural carotenoids has increased over the last few decades. In particular, it has been suggested that the use of bioprocessing technologies can improve carotenoid production yields or, as a minimum, increase the efficiency of currently used production processes. Thus, this review provides a short but comprehensive overview of the recent biotechnological developments in carotenoid production using microorganisms. The hot topics in the field are properly addressed, from carotenoid biosynthesis to the current technologies involved in their extraction, and even highlighting the recent advances in the marketing and application of "microbial" carotenoids. It is expected that this review will improve the knowledge and understanding of the most appropriate and economic strategies for a biotechnological production of carotenoids.
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6.
Fungal L-asparaginase: Strategies for production and food applications.
da Cunha, MC, Dos Santos Aguilar, JG, de Melo, RR, Nagamatsu, ST, Ali, F, de Castro, RJS, Sato, HH
Food research international (Ottawa, Ont.). 2019;:108658
Abstract
L-asparaginase (L-asparagine amidohydrolase EC 3.5.1.1) is of great importance in pharmaceutical and food applications. This review aims to describe the production and use of fungal L-asparaginase focusing on its potential as an effective reducer of acrylamide in different food applications. Fungal asparaginases have been used as food additives and have gained importance due to some technical advantages, for example, fungi can grow using low-cost culture mediums, and the enzyme is extracellular, which facilitates purification steps. Research aimed at the discovery of new L-asparaginases, mainly those produced by fungi, have great potential to obtain cheaper enzymes with desirable properties for application in food aiming at the reduction of acrylamide.
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7.
Endofungal Bacteria Increase Fitness of their Host Fungi and Impact their Association with Crop Plants.
Alabid, I, Glaeser, SP, Kogel, KH
Current issues in molecular biology. 2019;:59-74
Abstract
Endofungal bacteria are bacterial symbionts of fungi that exist within fungal hyphae and spores. There is increasing evidence that these bacteria, alone or in combination with their fungal hosts play a critical role in tripartite symbioses with plants, where they may contribute to plant growth and disease resistance to microbial pathogens. As the frequency of bacteria in fungi is commonly very low, breakthroughs in technology such as molecular taxonomy and laser scanning microscopy were required to establish the functional contribution of these bacteria in complex symbioses. Yet, the overall biological significance of endofungal bacteria is largely unknown and further progress in understanding is hampered by a very few biological systems where endofungal bacteria have been described mechanistically. We review here the current knowledge on endobacteria (EB) and their role in different types of fungal symbioses with plants. We show that various attempts to cure fungal cells from endobacteria failed, further suggesting that they play a crucial role in the symbiosis. Moreover, isolation of some of the endobacteria from their fungal hosts allowed confirming their autonomous beneficial activity such as plant growth promotion and resistance-inducing activity. The review addresses the potential agricultural significance of endofungal bacteria and their role in supporting sustainable agriculture by promoting plant growth, improving plant resistance, and decreasing yield loss caused by many microbial pathogens.
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8.
Microbial Pyrrolnitrin: Natural Metabolite with Immense Practical Utility.
Pawar, S, Chaudhari, A, Prabha, R, Shukla, R, Singh, DP
Biomolecules. 2019;(9)
Abstract
Pyrrolnitrin (PRN) is a microbial pyrrole halometabolite of immense antimicrobial significance for agricultural, pharmaceutical and industrial implications. The compound and its derivatives have been isolated from rhizospheric fluorescent or non-fluorescent pseudomonads, Serratia and Burkholderia. They are known to confer biological control against a wide range of phytopathogenic fungi, and thus offer strong plant protection prospects against soil and seed-borne phytopathogenic diseases. Although chemical synthesis of PRN has been obtained using different steps, microbial production is still the most useful option for producing this metabolite. In many of the plant-associated isolates of Serratia and Burkholderia, production of PRN is dependent on the quorum-sensing regulation that usually involves N-acylhomoserine lactone (AHL) autoinducer signals. When applied on the organisms as antimicrobial agent, the molecule impedes synthesis of key biomolecules (DNA, RNA and protein), uncouples with oxidative phosphorylation, inhibits mitotic division and hampers several biological mechanisms. With its potential broad-spectrum activities, low phototoxicity, non-toxic nature and specificity for impacts on non-target organisms, the metabolite has emerged as a lead molecule of industrial importance, which has led to developing cost-effective methods for the biosynthesis of PRN using microbial fermentation. Quantum of work narrating focused research efforts in the emergence of this potential microbial metabolite is summarized here to present a consolidated, sequential and updated insight into the chemistry, biology and applicability of this natural molecule.
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9.
Chitin Synthesis and Degradation in Fungi: Biology and Enzymes.
Yang, J, Zhang, KQ
Advances in experimental medicine and biology. 2019;:153-167
Abstract
Chitin is one of the most important carbohydrates of the fungal cell wall, and is synthesized by chitin synthases. Chitin can be degraded by chitinases, which are important virulence factors in pathogenic fungi. Knowledge about the biosynthesis and degradation of chitin, and the enzymes responsible, has accumulated in recent years. In this review, we analyze the amino acid sequences of chitin synthases from several typical fungi. These enzymes can be divided into seven groups. While the different chitin synthases from a single fungus share a low degree of similarity, the same type of chitin synthase from different fungi shows high similarity. The number of chitinase genes in fungi display wide variation, from a single gene in Schizosaccharomyces pombe, to 36 genes in Trichoderma virens. Chitinases from different fungi can be divided into four groups. The functions of chitin synthases and chitinases in several typical fungi are summarized, and the crystal structures of chitinases and chitinase modification are also discussed.
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10.
Grapevine trunk diseases under thermal and water stresses.
Songy, A, Fernandez, O, Clément, C, Larignon, P, Fontaine, F
Planta. 2019;(6):1655-1679
Abstract
Heat and water stresses, individually or combined, affect both the plant (development, physiology, and production) and the pathogens (growth, morphology, dissemination, distribution, and virulence). The grapevine response to combined abiotic and biotic stresses is complex and cannot be inferred from the response to each single stress. Several factors might impact the response and the recovery of the grapevine, such as the intensity, duration, and timing of the stresses. In the heat/water stress-GTDs-grapevine interaction, the nature of the pathogens, and the host, i.e., the nature of the rootstock, the cultivar and the clone, has a great importance. This review highlights the lack of studies investigating the response to combined stresses, in particular molecular studies, and the misreading of the relationship between rootstock and scion in the relationship GTDs/abiotic stresses. Grapevine trunk diseases (GTDs) are one of the biggest threats to vineyard sustainability in the next 30 years. Although many treatments and practices are used to manage GTDs, there has been an increase in the prevalence of these diseases due to several factors such as vineyard intensification, aging vineyards, or nursery practices. The ban of efficient treatments, i.e., sodium arsenite, carbendazim, and benomyl, in the early 2000s may be partly responsible for the fast spread of these diseases. However, GTD-associated fungi can act as endophytes for several years on, or inside the vine until the appearance of the first symptoms. This prompted several researchers to hypothesise that abiotic conditions, especially thermal and water stresses, were involved in the initiation of GTD symptoms. Unfortunately, the frequency of these abiotic conditions occurring is likely to increase according to the recent consensus scenario of climate change, especially in wine-growing areas. In this article, following a review on the impact of combined thermal and water stresses on grapevine physiology, we will examine (1) how this combination of stresses might influence the lifestyle of GTD pathogens, (2) learnings from grapevine field experiments and modelling aiming at studying biotic and abiotic stresses, and (3) what mechanistic concepts can be used to explain how these stresses might affect the grapevine plant status.