Phosphorus metabolism and transport in arbuscular mycorrhizal symbiosis

Saito, Katsuichi; Ezawa, Tatsuhiro

doi:10.1002/9781118951446.ch12

Cited by 15 publications

(14 citation statements)

References 126 publications

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“…This statement is founded on the fact that lipid biomarkers in the FC increased along with P in the plant tissues (Table 2); besides, both parameters positively correlated with the presence of arbuscules (Table 3). The arbuscules are shortlived structures with a turnover rate of 1-2 weeks (van Aarle and Olsson, 2003) and the interface between the plant and AMF (Wewer et al, 2014), where the P and photosynthates are exchanged in the periarbuscular space (Kobae et al, 2014;Saito and Ezawa, 2016). Thus, it would be consistent with the interpretation that P mobilization stimulated by the LMWOAs secretion was further supported by fungal growth and the exchange structures at the root level.…”

Section: Discussionsupporting

confidence: 72%

“…In all tomato roots mycorrhized with R. irregularis, we observed an arum-type AM association (Saito and Ezawa, 2016) FIGURE 4 | Mean values and standard errors for photosynthetic capacity (A max ) of Solanum lycopersicum L. leaves for the different available P sources and controls during the time course experiment. Three explicative boxes are included to differentiate the periods when we detected the AM plants acquired P from their respective sources.…”

Section: Fungal Growth and Degree Of Mycorrhizationmentioning

confidence: 88%

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Production of Organic Acids by Arbuscular Mycorrhizal Fungi and Their Contribution in the Mobilization of Phosphorus Bound to Iron Oxides

et al. 2021

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Most plants living in tropical acid soils depend on the arbuscular mycorrhizal (AM) symbiosis for mobilizing low-accessible phosphorus (P), due to its strong bonding by iron (Fe) oxides. The roots release low-molecular-weight organic acids (LMWOAs) as a mechanism to increase soil P availability by ligand exchange or dissolution. However, little is known on the LMWOA production by AM fungi (AMF), since most studies conducted on AM plants do not discriminate on the LMWOA origin. This study aimed to determine whether AMF release significant amounts of LMWOAs to liberate P bound to Fe oxides, which is otherwise unavailable for the plant. Solanum lycopersicum L. plants mycorrhized with Rhizophagus irregularis were placed in a bicompartmental mesocosm, with P sources only accessible by AMF. Fingerprinting of LMWOAs in compartments containing free and goethite-bound orthophosphate (OP or GOE-OP) and phytic acid (PA or GOE-PA) was done. To assess P mobilization via AM symbiosis, P content, photosynthesis, and the degree of mycorrhization were determined in the plant; whereas, AM hyphae abundance was determined using lipid biomarkers. The results showing a higher shoot P content, along with a lower N:P ratio and a higher photosynthetic capacity, may be indicative of a higher photosynthetic P-use efficiency, when AM plants mobilized P from less-accessible sources. The presence of mono-, di-, and tricarboxylic LMWOAs in compartments containing OP or GOE-OP and phytic acid (PA or GOE-PA) points toward the occurrence of reductive dissolution and ligand exchange/dissolution reactions. Furthermore, hyphae grown in goethite loaded with OP and PA exhibited an increased content of unsaturated lipids, pointing to an increased membrane fluidity in order to maintain optimal hyphal functionality and facilitate the incorporation of P. Our results underpin the centrality of AM symbiosis in soil biogeochemical processes, by highlighting the ability of the AMF and accompanying microbiota in releasing significant amounts of LMWOAs to mobilize P bound to Fe oxides.

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Section: Discussionsupporting

confidence: 72%

Section: Fungal Growth and Degree Of Mycorrhizationmentioning

confidence: 88%

Production of Organic Acids by Arbuscular Mycorrhizal Fungi and Their Contribution in the Mobilization of Phosphorus Bound to Iron Oxides

et al. 2021

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“…The recent understanding of the Pi uptake processes in AM fungi (reviewed in Saito & Ezawa, ) is represented in Fig. (a).…”

Section: Fine‐tuning Of Phosphate Homeostasismentioning

confidence: 99%

“…b). Another hypothesis, proposed by Saito & Ezawa (), is that polyP is directly exported to the interfacial apoplast via the VTC complex sorted to the plasma membrane and then hydrolyzed by plant ACP, which should also be addressed in the future.…”

Section: The Frontiers: Phosphate Translocation and Exportmentioning

confidence: 99%

How do arbuscular mycorrhizal fungi handle phosphate? New insight into fine‐tuning of phosphate metabolism

2018

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Contents Summary1116I.Introduction1116II.Foraging for phosphate1117III.Fine‐tuning of phosphate homeostasis1117IV.The frontiers: phosphate translocation and export1119V.Conclusions and outlook1120Acknowledgements1120References1120 Summary Arbuscular mycorrhizal fungi form symbiotic associations with most land plants and deliver mineral nutrients, in particular phosphate, to the host. Therefore, understanding the mechanisms of phosphate acquisition and delivery in the fungi is critical for full appreciation of the mutualism in this association. Here, we provide updates on physical, chemical, and biological strategies of the fungi for phosphate acquisition, including interactions with phosphate‐solubilizing bacteria, and those on the regulatory mechanisms of phosphate homeostasis based on resurveys of published genome sequences and a transcriptome with reference to the latest findings in a model fungus. For the mechanisms underlying phosphate translocation and export to the host, which are major research frontiers in this field, not only recent advances but also testable hypotheses are proposed. Lastly, we briefly discuss applicability of the latest tools to gene silencing in the fungi, which will be breakthrough techniques for comprehensive understanding of the molecular basis of fungal phosphate metabolism.

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“…Therefore, Pi is unloaded through either of the following four hypothetical pathways: (1) Pi is released from the vacuoles to the cytosol via exporter PHO91 and loaded to the Golgi/trans-Golgi network by PHO1-type Pi transporter for unloading to the PAS or apoplast; (2) the cytosol Pi is directly unloaded by PHO1-type Pi transporter localized on the plasma membrane of hyphae; (3) PolyP is directly exported via the VTC1/2/4 complex, sorted to the fungal plasma membrane to the PAS or apoplast, then hydrolyzed by plant acid phosphatase [ 9 , 214 ]; (4) Pi is exported from the fungus through proton-coupled Pi transporters [ 212 ]. Finally, Pi released to the PAS is acquired by the arbuscular mycorrhiza-inducible plant PHT1 family Pi transporters localized in the peri-arbuscular membrane (PAM) [ 172 , 215 , 216 ].…”

Section: Resultsmentioning

confidence: 99%

Genome-Wide Analysis of Nutrient Signaling Pathways Conserved in Arbuscular Mycorrhizal Fungi

Xiao-qin

Tang

et al. 2021

Microorganisms

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Arbuscular mycorrhizal (AM) fungi form a mutualistic symbiosis with a majority of terrestrial vascular plants. To achieve an efficient nutrient trade with their hosts, AM fungi sense external and internal nutrients, and integrate different hierarchic regulations to optimize nutrient acquisition and homeostasis during mycorrhization. However, the underlying molecular networks in AM fungi orchestrating the nutrient sensing and signaling remain elusive. Based on homology search, we here found that at least 72 gene components involved in four nutrient sensing and signaling pathways, including cAMP-dependent protein kinase A (cAMP-PKA), sucrose non-fermenting 1 (SNF1) protein kinase, target of rapamycin kinase (TOR) and phosphate (PHO) signaling cascades, are well conserved in AM fungi. Based on the knowledge known in model yeast and filamentous fungi, we outlined the possible gene networks functioning in AM fungi. These pathways may regulate the expression of downstream genes involved in nutrient transport, lipid metabolism, trehalase activity, stress resistance and autophagy. The RNA-seq analysis and qRT-PCR results of some core genes further indicate that these pathways may play important roles in spore germination, appressorium formation, arbuscule longevity and sporulation of AM fungi. We hope to inspire further studies on the roles of these candidate genes involved in these nutrient sensing and signaling pathways in AM fungi and AM symbiosis.

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Phosphorus metabolism and transport in arbuscular mycorrhizal symbiosis

Cited by 15 publications

References 126 publications

Production of Organic Acids by Arbuscular Mycorrhizal Fungi and Their Contribution in the Mobilization of Phosphorus Bound to Iron Oxides

Production of Organic Acids by Arbuscular Mycorrhizal Fungi and Their Contribution in the Mobilization of Phosphorus Bound to Iron Oxides

How do arbuscular mycorrhizal fungi handle phosphate? New insight into fine‐tuning of phosphate metabolism

Genome-Wide Analysis of Nutrient Signaling Pathways Conserved in Arbuscular Mycorrhizal Fungi

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