Strigolactones seem not to be involved in the nonsusceptibilty of arbuscular mycorrhizal (AM) nonhost plants to AM fungi

Although most land plants are hosts for arbuscular mycorrhizal fungi (AMF), a small number of plant families are arbuscular mycorrhizal (AM) nonhosts. There are indications that strigolactone levels in root exudates of AM nonhost plants are lower than in AM host plants, and it has been shown that in the strigolactone-deficient rms1 mutant (ccd8) of the AM host plant pea, the AMF colonization of roots is highly reduced. Application of the synthetic strigolactone analogue GR24 to this strigolactones-deficient mutant restored AMF colonization of roots. Our objective was to determine whether the application of GR24 to AM nonhost plants can affect their susceptibility to AMF. To test whether GR24 affects AMF colonization in our experimental system, we added GR24 to the strigolactone-deficient pea ccd8 mutant. Application of GR24 increased AMF colonization in the pea mutant to a similar level as in the pea wild type with normal strigolactone levels, showing clearly that in our experimental setup, application of the GR24 positively affects AMF colonization in strigolactone-deficient plants. Observation of cleared roots after application of GR24 to four AM nonhost plant species inoculated with the AMF Glomus intraradices showed that colonization did not occur.

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Rice phosphate transporters associated with phosphate uptake in rice roots colonised with arbuscular mycorrhizal fungi

Canadian Journal of Botany ◽

10.1139/b07-070 ◽

2007 ◽

Vol 85 (7) ◽

pp. 644-651 ◽

Cited By ~ 32

Author(s):

Donna Glassop ◽

Rosamond M. Godwin ◽

Sally E. Smith ◽

Frank W. Smith

Keyword(s):

Mycorrhizal Fungi ◽

Glomus Intraradices ◽

Rice Genome ◽

Arbuscular Mycorrhizal ◽

Am Fungi ◽

Growth Conditions ◽

Cortical Cells ◽

Symbiotic Associations ◽

Rice Roots ◽

Pi Acquisition

The completed rice-genome sequence was screened with a known inorganic phosphate (Pi) transporter sequence to reveal a family of 13 Pi transporters. This family can be used for studies into Pi acquisition and translocation throughout the plant. Plants that form symbiotic associations with arbuscular mycorrhizal (AM) fungi are of particular interest with respect to Pi acquisition because of their ability to utilize both direct and fungal pathways of uptake. Localization of transcripts of two Pi transporters by real-time RT-PCR and in situ hybridization were conducted in rice subjected to low Pi, high Pi, and AM colonization. One Pi transporter, ORYsa;Pht1;13, was detected in rice roots under all growth conditions. ORYsa;Pht1;11 was only expressed in roots colonized by AM fungi. Antisense RNA probes of ORYsa;Pht1;11 localized to cortical cells containing arbuscules and hyphal coils, formed by Glomus intraradices Schenck and Smith and Scutellospora calospora (Nicolson and Gerdemann) Walker and Sanders, respectively. Localization of the ORYsa;Pht1;13 probes was similar to that observed for ORYsa;Pht1;11 in colonized rice roots. This research proposes that at least two rice Pi transporters are involved in acquiring Pi via AM fungi, emphasising the complexity of Pi acquisition in plants with access to two Pi uptake pathways.

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Is cortical root colonization required for carbon transfer to arbuscular mycorrhizal fungi? Evidence from colonization phenotypes and spore production in the reduced mycorrhizal colonization (rmc) mutant of tomato

Botany ◽

10.1139/b08-043 ◽

2008 ◽

Vol 86 (9) ◽

pp. 1009-1019 ◽

Cited By ~ 10

Author(s):

Maria Manjarrez ◽

F. Andrew Smith ◽

Petra Marschner ◽

Sally E. Smith

Keyword(s):

Mycorrhizal Fungi ◽

Glomus Intraradices ◽

Arbuscular Mycorrhizal ◽

Am Fungi ◽

Mycorrhizal Colonization ◽

Fungal Mycelium ◽

Solanum Lycopersicum L ◽

Carbon Transfer ◽

External Mycelium ◽

First Time

For the first time, the phenotypes formed in the reduced mycorrhizal colonization (rmc) Solanum lycopersicum L. (tomato) mutant with different arbuscular mycorrhizal (AM) fungi were used to explore the potential of different fungal structures to support development of external fungal mycelium and spores. The life cycle of AM fungi with rmc was followed for up to 24 weeks. Results showed that production of external mycelium was slight and transitory for those fungi that did not penetrate the roots of rmc (Pen–) ( Glomus intraradices DAOM181602 and Glomus etunicatum ). For fungi that penetrated the root epidermis and hypodermis (Coi–, Glomus coronatum and Scutellospora calospora ) the mycelium produced varied in size, but was always smaller than with the wild-type 76R. Spores were formed by these fungi with 76R but not with rmc. The only fungus forming a Myc+ phenotype with rmc, G. intraradices WFVAM23, produced as much mycelium with rmc as with 76R. We observed lipid accumulation in hyphae and vesicles in both plant genotypes with this fungus. Mature spores were formed with 76R. However, with rmc, spores remained small and (presumably) immature for up to 24 weeks. We conclude that significant carbon transfer from plant to fungus can occur in Coi– interactions with rmc in which no cortical colonization occurs. We speculate that both carbon transfer and root signals are required for mature spores to be produced.

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Colonization and Growth Effects of the Mycorrhizal Fungus Glomus intraradicies in a Commercial Nursery Container Production System

Journal of Environmental Horticulture ◽

10.24266/0738-2898-18.4.247 ◽

2000 ◽

Vol 18 (4) ◽

pp. 247-251

Author(s):

F.T. Davies ◽

J.A. Saraiva Grossi ◽

L. Carpio ◽

A.A. Estrada-Luna

Keyword(s):

Production System ◽

Mycorrhizal Fungi ◽

Host Plants ◽

Glomus Intraradices ◽

Mycorrhizal Fungus ◽

Arbuscular Mycorrhizal ◽

Dry Mass ◽

Fertility Level ◽

Mycorrhizal Development ◽

Container Production

Abstract The objectives of this research were to demonstrate that mycorrhiza can survive in a commercial nursery container production system, and enhance plant productivity. Four species were used as host plants [Nandina domestica ‘Moon Bay’, Loropetalum chinense variety Rubrum ‘Hinepurpleleaf’ Plumb delight®, Salvia gregii, and Photinia fraseri]. Plants were inoculated with arbuscular mycorrhizal fungi, Glomus intraradices, and grown in a commercial nursery in Texas. For the first 5.5 months, plants were grown in #1 cans containing either 3 kg cu m (5 lbs cu yd) or 4.2 kg cu m (7 lbs cu yd) 24N–4P205–8K20. For the final 6.5 months of the study, plants were in larger containers, all of which contained 4.2 kg cu m (7 lbs cu yd) 24N–4P2O5–8K2O. The commercial inoculum of Glomus intraradices only enhanced growth of N. domestica. The shoot dry mass of mycorrhizal N. domestica plants at 3 kg cu m was the same as non-colonized plants at the higher fertility level of 4.2 cu m. Intraradical hyphae development and colonization (total arbuscules, vesicles/endospores, hyphae) of L. chinense, N. domestica, and S. gregii increased at the higher fertility levels. S. gregii had the greatest mycorrhizal development and a 216% increase in hyphae development and colonization at the higher fertility level.

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Elucidating the Mechanisms Underlying Enhanced Drought Tolerance in Plants Mediated by Arbuscular Mycorrhizal Fungi

Frontiers in Microbiology ◽

10.3389/fmicb.2021.809473 ◽

2021 ◽

Vol 12 ◽

Author(s):

Shen Cheng ◽

Ying-Ning Zou ◽

Kamil Kuča ◽

Abeer Hashem ◽

Elsayed Fathi Abd_Allah ◽

...

Keyword(s):

Drought Stress ◽

Drought Tolerance ◽

Mycorrhizal Fungi ◽

Host Plants ◽

Molecular Mechanisms ◽

Arbuscular Mycorrhizal ◽

Am Fungi ◽

Host Cells ◽

Future Research ◽

Symbiotic Association

Plants are often subjected to various environmental stresses during their life cycle, among which drought stress is perhaps the most significant abiotic stress limiting plant growth and development. Arbuscular mycorrhizal (AM) fungi, a group of beneficial soil fungi, can enhance the adaptability and tolerance of their host plants to drought stress after infecting plant roots and establishing a symbiotic association with their host plant. Therefore, AM fungi represent an eco-friendly strategy in sustainable agricultural systems. There is still a need, however, to better understand the complex mechanisms underlying AM fungi-mediated enhancement of plant drought tolerance to ensure their effective use. AM fungi establish well-developed, extraradical hyphae on root surfaces, and function in water absorption and the uptake and transfer of nutrients into host cells. Thus, they participate in the physiology of host plants through the function of specific genes encoded in their genome. AM fungi also modulate morphological adaptations and various physiological processes in host plants, that help to mitigate drought-induced injury and enhance drought tolerance. Several AM-specific host genes have been identified and reported to be responsible for conferring enhanced drought tolerance. This review provides an overview of the effect of drought stress on the diversity and activity of AM fungi, the symbiotic relationship that exists between AM fungi and host plants under drought stress conditions, elucidates the morphological, physiological, and molecular mechanisms underlying AM fungi-mediated enhanced drought tolerance in plants, and provides an outlook for future research.

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Fungal Lipid Accumulation and Development of Mycelial Structures by Two Arbuscular Mycorrhizal Fungi

Applied and Environmental Microbiology ◽

10.1128/aem.69.11.6762-6767.2003 ◽

2003 ◽

Vol 69 (11) ◽

pp. 6762-6767 ◽

Cited By ~ 91

Author(s):

Ingrid M. van Aarle ◽

Pål Axel Olsson

Keyword(s):

Fatty Acid ◽

Mycorrhizal Fungi ◽

Glomus Intraradices ◽

Neutral Lipids ◽

Phospholipid Fatty Acid ◽

Plantago Lanceolata ◽

Arbuscular Mycorrhizal ◽

Am Fungi ◽

Fungal Species ◽

Opposite Pattern

ABSTRACT We monitored the development of intraradical and extraradical mycelia of the arbuscular mycorrhizal (AM) fungi Scutellospora calospora and Glomus intraradices when colonizing Plantago lanceolata. The occurrence of arbuscules (branched hyphal structures) and vesicles (lipid storage organs) was compared with the amounts of signature fatty acids. The fatty acid 16:1ω5 was used as a signature for both AM fungal phospholipids (membrane constituents) and neutral lipids (energy storage) in roots (intraradical mycelium) and in soil (extraradical mycelium). The formation of arbuscules and the accumulation of AM fungal phospholipids in intraradical mycelium followed each other closely in both fungal species. In contrast, the neutral lipids of G. intraradices increased continuously in the intraradical mycelium, while vesicle occurrence decreased after initial rapid root colonization by the fungus. S. calospora does not form vesicles and accumulated more neutral lipids in extraradical than in intraradical mycelium, while the opposite pattern was found for G. intraradices. G. intraradices allocated more of its lipids to storage than did S. calospora. Thus, within a species, the fatty acid 16:1ω5 is a good indicator for AM fungal development. The phospholipid fatty acid 16:1ω5 is especially suitable for indicating the frequency of arbuscules in the symbiosis. We propose that the ratio of neutral lipids to phospholipids is more important than is the presence of vesicles in determining the storage status of AM fungi.

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Germinating Spore Exudates from Arbuscular Mycorrhizal Fungi: Molecular and Developmental Responses in Plants and Their Regulation by Ethylene

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-06-10-0146 ◽

2011 ◽

Vol 24 (2) ◽

pp. 260-270 ◽

Cited By ~ 63

Author(s):

Arijit Mukherjee ◽

Jean-Michel Ané

Keyword(s):

Gene Expression ◽

Genetic Control ◽

Root Development ◽

Mycorrhizal Fungi ◽

Root Architecture ◽

Glomus Intraradices ◽

Arbuscular Mycorrhizal ◽

Am Fungi ◽

Plant Responses ◽

Symbiotic Gene

Arbuscular mycorrhizal (AM) fungi stimulate root development and induce expression of mycorrhization-specific genes in both eudicots and monocots. Diffusible factors released by AM fungi have been shown to elicit similar responses in Medicago truncatula. Colonization of roots by AM fungi is inhibited by ethylene. We compared the effects of germinating spore exudates (GSE) from Glomus intraradices in monocots and in eudicots, their genetic control, and their regulation by ethylene. GSE modify root architecture and induce symbiotic gene expression in both monocots and eudicots. The genetic regulation of root architecture and gene expression was analyzed using M. truncatula and rice symbiotic mutants. These responses are dependent on the common symbiotic pathway as well as another uncharacterized pathway. Significant differences between monocots and eudicots were observed in the genetic control of plant responses to GSE. However, ethylene inhibits GSE-induced symbiotic gene expression and root development in both groups. Our results indicate that GSE signaling shares similarities and differences in monocots versus eudicots, that only a subset of AM signaling pathways has been co-opted in legumes for the establishment of root nodulation with rhizobia, and that regulation of these pathways by ethylene is a feature conserved across higher land plants.

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Mycorrhizal Fungi Enhance Resistance to Herbivores in Tomato Plants with Reduced Jasmonic Acid Production

Agronomy ◽

10.3390/agronomy9030131 ◽

2019 ◽

Vol 9 (3) ◽

pp. 131 ◽

Cited By ~ 4

Author(s):

Ludovico Formenti ◽

Sergio Rasmann

Keyword(s):

Plant Growth ◽

Jasmonic Acid ◽

Plant Resistance ◽

Mycorrhizal Fungi ◽

Arbuscular Mycorrhizal ◽

Am Fungi ◽

Wild Type ◽

Tomato Plants ◽

Solanum Lycopersicum L ◽

Fungal Inoculation

Arbuscular mycorrhizal (AM) fungi favor plant growth by improving nutrient acquisition, but also by increasing their resistance against abiotic and biotic stressors, including herbivory. Mechanisms of AM fungal mediated increased resistance include a direct effect of AM fungi on plant vigor, but also a manipulation of the hormonal cascades, such as the systemic activation of jasmonic acid (JA) dependent defenses. However, how AM fungal inoculation and variation in the endogenous JA production interact to produce increased resistance against insect herbivores remains to be further elucidated. To address this question, three genotypes of Solanum lycopersicum L., a JA-biosynthesis deficient mutant, a JA over-accumulating mutant, and their wild-type were either inoculated with AM fungi or left un-inoculated. Plant growth-related traits and resistance against Spodoptera littoralis (Boisduval) caterpillars, a major crop pest, were measured. Overall, we found that deficiency in JA production reduced plant development and were the least resistant against S. littoralis. Moreover, AM fungi increased plant resistance against S. littoralis, but such beneficial effect was more pronounced in JA-deficient plant than on JA over-accumulating plants. These results highlight that AM fungi-driven increased plant resistance is negatively affected by the ability of plants to produce JA and that AM fungi complement JA-mediated endogenous plant defenses in this system.

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Isolation of a Premycorrhizal Infection (pmi2) Mutant of Tomato, Resistant to Arbuscular Mycorrhizal Fungal Colonization

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi.2003.16.5.382 ◽

2003 ◽

Vol 16 (5) ◽

pp. 382-388 ◽

Cited By ~ 64

Author(s):

Rakefet David-Schwartz ◽

Vijay Gadkar ◽

Smadar Wininger ◽

Roza Bendov ◽

Gad Galili ◽

...

Keyword(s):

Mycorrhizal Fungi ◽

Arbuscular Mycorrhizae ◽

Glomus Intraradices ◽

Arbuscular Mycorrhizal ◽

Plant Roots ◽

Fungal Colonization ◽

Recessive Trait ◽

Wild Type ◽

Arbuscular Mycorrhizal Fungal

Arbuscular mycorrhizae (AM) represent an ancient symbiosis between mycorrhizal fungi and plant roots which co-evolved to exhibit a finely tuned, multistage interaction that assists plant growth. Direct screening efforts for Myc¯ plant mutants resulted in the identification of a tomato (Lycopersicon esculentum L. cv. Micro-Tom) mutant, M20, which was impaired in its ability to support the premycorrhizal infection (pmi) stages. The Myc¯ phenotype of the M20 mutant was a single Mendelian recessive trait, stable for nine generations, and nonallelic to a previously identified M161 pmi mutant. The M20 mutant was resistant to infection by isolated AM spores and colonized roots. Formation of Glomus intraradices appressoria on M20 roots was normal, as on wild-type (WT) plants, but in significantly reduced numbers. A significant reduction in spore germination was observed in vitro in the presence of M20 exudates relative to WT. Our results indicate that this new mutant shares similar physiological characteristics with the M161 pmi mutant, but has a more suppressive Myc¯ phenotype response.

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Suppression of fungal and nematode plant pathogens through arbuscular mycorrhizal fungi

Biology Letters ◽

10.1098/rsbl.2011.0874 ◽

2011 ◽

Vol 8 (2) ◽

pp. 214-217 ◽

Cited By ~ 91

Author(s):

Stavros D. Veresoglou ◽

Matthias C. Rillig

Keyword(s):

Mycorrhizal Fungi ◽

Fungal Pathogens ◽

Host Plants ◽

Plant Pathogens ◽

Meta Analysis ◽

Arbuscular Mycorrhizal ◽

Am Fungi ◽

Terrestrial Plants ◽

Pathogen Suppression ◽

Mycorrhizal Ecology

Arbuscular mycorrhizal (AM) fungi represent ubiquitous mutualists of terrestrial plants. Through the symbiosis, plant hosts, among other benefits, receive protection from pathogens. A meta-analysis was conducted on 106 articles to determine whether, following pathogen infection of AM-colonized plants, the identity of the organisms involved (pathogens, AM fungi and host plants) had implications for the extent of the AM-induced pathogen suppression. Data on fungal and nematode pathogens were analysed separately. Although we found no differences in AM effectiveness with respect to the identity of the plant pathogen, the identity of the AM isolate had a dramatic effect on the level of pathogen protection. AM efficiency differences with respect to nematode pathogens were mainly limited to the number of AM isolates present; by contrast, modification of the ability to suppress fungal pathogens could occur even through changing the identity of the Glomeraceae isolate applied. N-fixing plants received more protection from fungal pathogens than non-N-fixing dicotyledons; this was attributed to the more intense AM colonization in N-fixing plants. Results have implications for understanding mycorrhizal ecology and agronomic applications.

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Different arbuscular mycorrhizal fungi induce differences in cellular responses and fungal activity in a mycorrhiza-defective mutant of tomato (rmc)

Functional Plant Biology ◽

10.1071/fp08032 ◽

2009 ◽

Vol 36 (1) ◽

pp. 86 ◽

Cited By ~ 9

Author(s):

Maria Manjarrez ◽

Meredith Wallwork ◽

Sally E. Smith ◽

F. Andrew Smith ◽

Sandy Dickson

Keyword(s):

Mycorrhizal Fungi ◽

Laser Scanning ◽

Plant Defence ◽

Arbuscular Mycorrhizal ◽

Am Fungi ◽

Cellular Responses ◽

Wild Type ◽

Nuclear Movement ◽

Callose Deposition ◽

Defence Responses

The reduced mycorrhizal colonisation (rmc) mutant of tomato forms different phenotypes with different arbuscular mycorrhizal (AM) fungi. Our aim was to characterise microscopically the cellular responses in plant and fungus in order to reveal how these varied when colonisation was blocked at different stages. Synchronised colonisation coupled with vital staining, autofluorescence and laser scanning confocal microscopy (LSCM) were used to determine how long the AM fungi stay alive during the interactions with rmc, whether nuclear repositioning occurred in the same way as in wild-type interactions and whether there was evidence for deployment of defence responses. The results showed that (1) all the AM fungi tested were attracted to roots of rmc, on which they developed active external mycelium and appressoria, the latter sometimes in higher numbers than on the wild type; (2) plant cellular responses, such as nuclear movement, occurred only when the AM fungus was able to penetrate the epidermal cells of rmc; and (3) plant defence responses such as autofluorescence were observed only transiently and callose deposition was not involved in blocking AM fungi in rmc. The results demonstrate that multi-step AM colonisation is not only an outcome of cellular processes influenced by both plant and fungus, but is also modified by the capacity of different AM fungi to respond to the plant phenotype induced by the rmc mutation.

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