Specificity in the Arbuscular Mycorrhizal Symbiosis

Sanders, Ian R.

doi:10.1007/978-3-540-38364-2_16

Cited by 58 publications

(38 citation statements)

References 47 publications

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“…This approach is promising, particularly if applied in conjunction with quantitative real-time PCR (qPCR) (17), which allows for the determination of the abundance of the fungal taxa in samples. Studies using qPCR with taxon-specific primers demonstrated that qPCR is a more sensitive tool to monitor community changes than commonly used nested endpoint PCR (3,19,29), and it corroborated the callings for the quantitative evaluation of AM fungal communities (11,32).…”

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confidence: 65%

Intraradical Dynamics of Two Coexisting Isolates of the Arbuscular Mycorrhizal Fungus Glomus intraradices Sensu Lato as Estimated by Real-Time PCR of Mitochondrial DNA

Krak

Janoušková

Caklová

et al. 2012

Appl Environ Microbiol

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bReal-time PCR in nuclear ribosomal DNA (nrDNA) is becoming a well-established tool for the quantification of arbuscular mycorrhizal (AM) fungi, but this genomic region does not allow the specific amplification of closely related genotypes. The large subunit of mitochondrial DNA (mtDNA) has a higher-resolution power, but mtDNA-based quantification has not been previously explored in AM fungi. We applied real-time PCR assays targeting the large subunit of mtDNA to monitor the DNA dynamics of two isolates of Glomus intraradices sensu lato coexisting in the roots of medic (Medicago sativa). The mtDNA-based quantification was compared to quantification in nrDNA. The ratio of copy numbers determined by the nrDNA-and mtDNA-based assays consistently differed between the two isolates. Within an isolate, copy numbers of the nuclear and the mitochondrial genes were closely correlated. The two quantification approaches revealed similar trends in the dynamics of both isolates, depending on whether they were inoculated alone or together. After 12 weeks of cultivation, competition between the two isolates was observed as a decrease in the mtDNA copy numbers of one of them. The coexistence of two closely related isolates, which cannot be discriminated by nrDNA-based assays, was thus identified as a factor influencing the dynamics of AM fungal DNA in roots. Taken together, the results of this study show that real-time PCR assays targeted to the large subunit of mtDNA may become useful tools for the study of coexisting AM fungi. Communities of arbuscular mycorrhizal (AM) fungi are an integral component of the soil-plant system, colonizing the roots of the majority of land plants, facilitating plant nutrient uptake, and constituting an important channel of carbon movement from plants to soil (35). The PCR amplification of AM fungal DNA with taxon-specific primers enables the targeted detection of AM fungal taxa within a community and detailed studies of their coexistence involving the screening of large sample sets (21,37,47). This approach is promising, particularly if applied in conjunction with quantitative real-time PCR (qPCR) (17), which allows for the determination of the abundance of the fungal taxa in samples. Studies using qPCR with taxon-specific primers demonstrated that qPCR is a more sensitive tool to monitor community changes than commonly used nested endpoint PCR (3,19,29), and it corroborated the callings for the quantitative evaluation of AM fungal communities (11, 32).The qPCR assays that have been developed so far for the quantification of AM fungal DNA in roots or in soil rely, with one exception (12), on nuclear markers in the relatively well-characterized nuclear ribosomal DNA (nrDNA). This region, however, lacks the resolution power to discriminate among closely related species, such as Glomus claroideum and G. etunicatum (8,44), or even isolates of the same species. It is known that high developmental and functional diversity exists at these lower taxonomic levels in AM fungi (20,28), but interactions amon...

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confidence: 65%

Intraradical Dynamics of Two Coexisting Isolates of the Arbuscular Mycorrhizal Fungus Glomus intraradices Sensu Lato as Estimated by Real-Time PCR of Mitochondrial DNA

Krak

Janoušková

Caklová

et al. 2012

Appl Environ Microbiol

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“…Finally, different hosts can produce different effects on the growth and spore production of any given AMF species. These studies show that different combinations of AMF and host species are functionally different, and these properties of AMF-host plant interactions can contribute to the generation and maintenance of aboveground host diversity (Schneck and Smith 1982, Mosse 1992, Bever et al 1996, van der Heijden et al 1998a, b, Kiers et al 2000, Klironomos et al 2000, Bever 2002, Klironomos 2002, Sanders 2002, Herre et al 2005a.…”

Section: Life Cycle and General Natural History Of Tropical Arbusculamentioning

confidence: 99%

Ecological Implications of Anti-Pathogen Effects of Tropical Fungal Endophytes and Mycorrhizae

Herre

Mejía

Kyllo

et al. 2007

Ecology

256

185

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We discuss studies of foliar endophytic fungi (FEF) and arbuscular mycorrhizal fungi (AMF) associated with Theobroma cacao in Panama. Direct, experimentally controlled comparisons of endophyte free (E−) and endophyte containing (E+) plant tissues in T. cacao show that foliar endophytes (FEF) that commonly occur in healthy host leaves enhance host defenses against foliar damage due to the pathogen (Phytophthora palmivora). Similarly, root inoculations with commonly occurring AMF also reduce foliar damage due to the same pathogen. These results suggest that endophytic fungi can play a potentially important mutualistic role by augmenting host defensive responses against pathogens. There are two broad classes of potential mechanisms by which endophytes could contribute to host protection: (1) inducing or increasing the expression of intrinsic host defense mechanisms and (2) providing additional sources of defense, extrinsic to those of the host (e.g., endophyte‐based chemical antibiosis). The degree to which either of these mechanisms predominates holds distinct consequences for the evolutionary ecology of host–endophyte–pathogen relationships. More generally, the growing recognition that plants are composed of a mosaic of plant and fungal tissues holds a series of implications for the study of plant defense, physiology, and genetics.

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“…Arbuscular mycorrhizal (AM) associations are generally considered to be nonspecific, as the same AMF species is able to colonize the roots of different host plants, which in turn can be colonized by various AMF species (13,38,52). However, results from some studies show that preferential associations between plants and AMF may exist (4,7,13,32,56), and reciprocal interactions between AMF and the plant community, based on reciprocal feedback, have been proposed (2,3,4).…”

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confidence: 99%

Preferential Colonization ofSolanum tuberosumL. Roots by the FungusGlomus intraradicesin Arable Soil of a Potato Farming Area

Cesaro

Tuinen

Copetta

et al. 2008

Appl Environ Microbiol

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The symbiosis between plant roots and arbuscular mycorrhizal (AM) fungi has been shown to affect both the diversity and productivity of agricultural communities. In this study, we characterized the AM fungal communities of Solanum tuberosum L. (potato) roots and of the bulk soil in two nearby areas of northern Italy, in order to verify if land use practices had selected any particular AM fungus with specificity to potato plants. The AM fungal large-subunit (LSU) rRNA genes were subjected to nested PCR, cloning, sequencing, and phylogenetic analyses. One hundred eighty-three LSU rRNA sequences were analyzed, and eight monophyletic ribotypes, belonging to Glomus groups A and B, were identified. AM fungal communities differed between bulk soil and potato roots, as one AM fungal ribotype, corresponding to Glomus intraradices, was much more frequent in potato roots than in soils (accounting for more than 90% of sequences from potato samples and less than 10% of sequences from soil samples). A semiquantitative heminested PCR with specific primers was used to confirm and quantify the AM fungal abundance observed by cloning. Overall results concerning the biodiversity of AM fungal communities in roots and in bulk soils from the two studied areas suggested that potato roots were preferentially colonized by one AM fungal species, G. intraradices.Arbuscular mycorrhizal fungi (AMF) are obligate biotrophs, forming mutualistic relationships with a broad range of host plant species (42). Arbuscular mycorrhizal (AM) associations are generally considered to be nonspecific, as the same AMF species is able to colonize the roots of different host plants, which in turn can be colonized by various AMF species (13, 38, 52). However, results from some studies show that preferential associations between plants and AMF may exist (4,7,13,32,56), and reciprocal interactions between AMF and the plant community, based on reciprocal feedback, have been proposed (2,3,4). In particular, differential responses by plant species to individual isolates and species of AMF (43), leading to variations in the plant community composition and productivity and depending on the diversity and identity of the AMF (23, 51), have been observed previously.Although most plants used in agriculture and horticulture form arbuscular mycorrhizae, agricultural management practices may affect the composition and diversity of AMF communities, as well as spore and mycelium densities, in both temperate and tropical agroecosystems (24). In general, agricultural practices have a negative impact on the AM association (8, 14); AMF abundance is reduced by phosphorus (P) fertilization (14, 33) and by crop cultivation, due mainly to either mechanical disturbance by tillage or a change of host plants in crop rotation systems. Moreover, seasonal variations in the abundance of AMF in agricultural soil have been observed (22).Few data are available concerning potato plants and AMF. The influence of AMF species on the potato response to P nutrition (25, 26) and the effect on tuber yi...

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Specificity in the Arbuscular Mycorrhizal Symbiosis

Cited by 58 publications

References 47 publications

Intraradical Dynamics of Two Coexisting Isolates of the Arbuscular Mycorrhizal Fungus Glomus intraradices Sensu Lato as Estimated by Real-Time PCR of Mitochondrial DNA

Intraradical Dynamics of Two Coexisting Isolates of the Arbuscular Mycorrhizal Fungus Glomus intraradices Sensu Lato as Estimated by Real-Time PCR of Mitochondrial DNA

Ecological Implications of Anti-Pathogen Effects of Tropical Fungal Endophytes and Mycorrhizae

Preferential Colonization ofSolanum tuberosumL. Roots by the FungusGlomus intraradicesin Arable Soil of a Potato Farming Area

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