Carbon Metabolism and Transport in Arbuscular Mycorrhizas

Bago, Berta; Pfeffer, Philip E.; Shachar‐Hill, Yair

doi:10.1104/pp.124.3.949

Cited by 488 publications

(349 citation statements)

References 71 publications

(42 reference statements)

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“…The mutualistic nature of their interaction with plants is based on nutritional exchanges: as obligate biotrophs, AM fungi depend on a carbon flux from plants, which has been estimated as 5 billion tons per year (Bago et al, 2000). In return, AM fungi supply plants with nutrients directly taken up from the soil thanks to a network of extraradical hyphae that provide an extensive surface area for water and nutrient absorption (Giovannetti et al, 2004).…”

mentioning

confidence: 99%

A Mycorrhizal-Specific Ammonium Transporter from Lotus japonicus Acquires Nitrogen Released by Arbuscular Mycorrhizal Fungi

et al. 2009

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In mycorrhizal associations, the fungal partner assists its plant host by providing nitrogen (N) in addition to phosphate. Arbuscular mycorrhizal (AM) fungi have access to inorganic or organic forms of N and translocate them via arginine from the extra-to the intraradical mycelium, where the N is transferred to the plant without any carbon skeleton. However, the molecular form in which N is transferred, as well as the involved mechanisms, is still under debate. NH 4 + seems to be the preferential transferred molecule, but no plant ammonium transporter (AMT) has been identified so far. Here, we offer evidence of a plant AMT that is involved in N uptake during mycorrhiza symbiosis. The gene LjAMT2;2, which has been shown to be the highest up-regulated gene in a transcriptomic analysis of Lotus japonicus roots upon colonization with Gigaspora margarita, has been characterized as a high-affinity AMT belonging to the AMT2 subfamily. It is exclusively expressed in the mycorrhizal roots, but not in the nodules, and transcripts have preferentially been located in the arbusculated cells. Yeast (Saccharomyces cerevisiae) mutant complementation has confirmed its functionality and revealed its dependency on acidic pH. The transport experiments using Xenopus laevis oocytes indicated that, unlike other plant AMTs, LjAMT2;2 transports NH 3 instead of NH 4 + . Our results suggest that the transporter binds charged ammonium in the apoplastic interfacial compartment and releases the uncharged NH 3 into the plant cytoplasm. The implications of such a finding are discussed in the context of AM functioning and plant phosphorus uptake.

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confidence: 99%

A Mycorrhizal-Specific Ammonium Transporter from Lotus japonicus Acquires Nitrogen Released by Arbuscular Mycorrhizal Fungi

et al. 2009

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“…Hyphal elongation ranges from a few millimeters to a few centimeters. During this asymbiotic stage, the fungus seems to consume a minimum of its stored carbon and energy (Bécard and Piché, 1989a;Bago et al, 1999Bago et al, , 2000. In the presence of a host plant, but still before physical contact with the root, fungal growth pattern changes and intense presymbiotic branching can be observed.…”

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confidence: 99%

Root Factors Induce Mitochondrial-Related Gene Expression and Fungal Respiration during the Developmental Switch from Asymbiosis to Presymbiosis in the Arbuscular Mycorrhizal FungusGigaspora rosea

et al. 2003

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During spore germination, arbuscular mycorrhizal (AM) fungi show limited hyphal development in the absence of a host plant (asymbiotic). In the presence of root exudates, they switch to a new developmental stage (presymbiotic) characterized by extensive hyphal branching. Presymbiotic branching of the AM fungus Gigaspora rosea was induced in liquid medium by a semipurified exudate fraction from carrot (Daucus carota) root organ cultures. Changes in RNA accumulation patterns were monitored by differential display analysis. Differentially appearing cDNA fragments were cloned and further analyzed. Five cDNA fragments could be identified that show induced RNA accumulation 1 h after the addition of root exudate. Sequence similarities of two fragments to mammalian Nco4 and mitochondrial rRNA genes suggested that root exudates could influence fungal respiratory activity. To support this hypothesis, additional putative mitochondrial related-genes were shown to be induced by root exudates. These genes were identified after subtractive hybridization and putatively encode a pyruvate carboxylase and a mitochondrial ADP/ATP translocase. The gene GrosPyc1 for the pyruvate carboxylase was studied in more detail by cloning a cDNA and by quantifying its RNA accumulation. The hypothesis that respiratory activity of AM fungi is stimulated by root exudates was confirmed by physiological and cytological analyses in G. rosea and Glomus intraradices. Oxygen consumption and reducing activity of both fungi was induced after 3 and 2 h of exposition with the root factor, respectively, and the first respiration activation was detected in G. intraradices after approximately 90 min. In addition, changes in mitochondrial morphology, orientation, and overall biomass were detected in G. rosea after 4 h. In summary, the root-exuded factor rapidly induces the expression of certain fungal genes and, in turn, fungal respiratory activity before intense branching. This defines the developmental switch from asymbiosis to presymbiosis, first by gene activation (0.5-1 h), subsequently on the physiological level (1.5-3 h), and finally as a morphological response (after 5 h).Arbuscular mycorrhizal (AM) fungi are obligate biotrophic root symbionts that cannot be propagated in pure culture. Therefore, they are difficult to study, and analyses concerning the structure and the function of their genes are rare and mainly based on PCR techniques (Franken and Requena, 2001). Establishment of the symbiosis after spore germination includes hyphal branching, appressorium development after contacting the root, symbiotic colonization of the cortex, formation of the intracellular arbuscules, and, concomitantly, production of a sporulative extraradical mycelium (Bianciotto and Bonfante, 1998; Smith and Read, 1997). These developmental stages presumably require molecular communication between the fungus and the plant. Signals should be exchanged between the partners, leading to stagespecific patterns of gene expression. The corresponding gene products in turn would be re...

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“…In these associations, the plants provide carbon and lipids for the growth and function of fungi (Bago et al 2000; Jiang et al 2017), and thus can influence the fungal community via host specificity, producing diverse organic substrates and modifying microhabitats. In return, mycorrhizal fungi improve plant nutrient (particularly in nitrogen and phosphorus) and water uptake and resistance to biotic and abiotic stresses, and they therefore influence plant diversity, productivity, and ecosystem functioning by forming underground common mycorrhizal networks that connected individuals of plants.…”

Section: Mycorrhizaementioning

confidence: 99%

Presidential address: recent advance of mycorrhizal research in China

Guo

2018

Mycology

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I am honoured to address as the seventh president of the Mycological Society of China. Mycorrhizal research has a long history in China, including taxonomy, diversity, ecology, molecular biology, and application. Particularly in the past four decades, great progress in mycorrhizal field has been made by Chinese mycologists and ecologists. In this paper, through my own experience, I summarised the main and important advance of recent mycorrhizal researches in terms of mycorrhizal fungal diversity, community, responses to global environmental changes, molecular biology, and function in China. Some perspectives are also proposed for future mycorrhizal studies in China.

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Carbon Metabolism and Transport in Arbuscular Mycorrhizas

Cited by 488 publications

References 71 publications

A Mycorrhizal-Specific Ammonium Transporter from Lotus japonicus Acquires Nitrogen Released by Arbuscular Mycorrhizal Fungi

A Mycorrhizal-Specific Ammonium Transporter from Lotus japonicus Acquires Nitrogen Released by Arbuscular Mycorrhizal Fungi

Root Factors Induce Mitochondrial-Related Gene Expression and Fungal Respiration during the Developmental Switch from Asymbiosis to Presymbiosis in the Arbuscular Mycorrhizal FungusGigaspora rosea

Presidential address: recent advance of mycorrhizal research in China

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