A rapid and highly sensitive method for measuring enzyme activities in single mycorrhizal tips using 4-methylumbelliferone-labelled fluorogenic substrates in a microplate system

103

Abstract· Introduction Important nutrients in forest soils such as nitrogen and phosphorus are mostly recycled from natural polymeric compounds contained in litter and organic debrisfor example nucleic acids, proteins, or chitin.· Objectives Activities of enzymes such as phosphatases, proteases, cellulases, chitinases and laccase were shown in saprotrophic but also in ectomycorrhizal fungi and there is increasing evidence that these enzymes contribute not only to the functioning of the symbiosis but also to the mobilisation of nutrients. In the present review, we describe how enzyme secretion and localisation on fungal hyphae may be connected to the potential role in soil nutrient cycling. · ResultsRecently developed methods for enzyme activity studies of ectomycorrhizae directly assayed in or collected from the field such as enzyme activity profiling and soil imprinting are described. Their value and limitations in different examples of ecological studies is highlighted and discussed also with respect to the role of other soil microorganisms associated with ectomycorrhizae. · ConclusionThe conclusion from our review is that enzyme activities of ECM and their associated microorganisms provide a potentially enormous plasticity of mycorrhizosphere functionality which is an open field for further research. Enzymes secrétés par les champignons ectomycorhiziens et exploitation des éléments minéraux contenus dans la matière organique du sol.

Section: Possible Mechanisms Used By Ecm Fungi To Secrete Extracellulmentioning

confidence: 99%

Enzyme secretion by ECM fungi and exploitation of mineral nutrients from soil organic matter

Pritsch

Garbaye

2011

103

“…Experimental site of Champenoux Fourteen ECM tips of each morphotype (chosen among the most turgid and healthy-looking ones, from a pooled sample of those of the six soil cores in which this ECM type was present) were used to determine their potential enzymatic activities, using the high-throughput photometric and fluorimetric microplate assays described by Pritsch et al (2004) and Courty et al (2005), and applied in previous studies (Buée et al 2007). Each well of the 96-well micro-titration plate contained a single ECM tip.…”

Section: Enzymatic Activity Profiling Of Ecmsmentioning

confidence: 99%

“…Enzymatic activities were measured on all ECM species presenting more than seven healthy root tips after pooling, in order to have enough ECM material for the enzymatic assays. Here, the high-throughput assay described by Pritsch et al (2004) and Courty et al (2005) was modified. The eight enzymatic activities previously described were sequentially measured on the seven selected tips.…”

Section: Enzymatic Activity Profiling Of Ecmsmentioning

confidence: 99%

Secreted enzymatic activities of ectomycorrhizal fungi as a case study of functional diversity and functional redundancy

Rineau¹,

Courty

2011

Abstract• Introduction Many studies deal with taxonomic diversity (TD) or estimation of functional traits of ectomycorrhizal communities. However, to our knowledge, none of them has ever tried to calculate the functional diversity (FD) of those communities, which is of critical importance for the diversity and reliability of nutrient supply to the tree.• Objectives Here, we propose to evaluate the functional diversity of ECM communities in their potential ability to mobilise nutrients from organic matter, in two different forest stands.• Results Results show that in both forest stands:-TD is strongly correlated with FD.-ECM species are functionally redundant within the communities for their abilities to secrete organic matter degrading enzymes. -The functional traits (enzymatic activities) of the studied ectomycorrhizal communities are not related within genera, nor within families or phylogenetically related groups of taxa. -Some species show a wide phenotypic plasticity for their enzymatic profiles.• Conclusion This study provides the first evidence of functional redundancy in ectomycorrhizal communities. More studies are now needed to evaluate the robustness of these results at wider ecosystem scales and using other relevant functional traits.

“…Regarding the mobilisation of organic P, the extensive use of microplate assay (Pritsch et al 2004;Pritsch and Garbaye 2011, this issue) for measuring acid phosphatase activities on individual root tips, together with the molecular identification of the fungal species forming the ectomycorrhizal tip, should be a valuable tool to extend our knowledge about the factors that regulate the abundance of phosphatases released into the soil. Alternatively, molecular tools could be designed to study the diversity of these enzymes in the field.…”

Section: Discussionmentioning

confidence: 99%

“…Depending on their substrate, the enzymes can be phosphomonoesterases or phosphodiesterases. Most of the studies addressing the release of phosphatases use artificial phosphomonesters such as p-nitrophenyl phosphate (pNPP) based on the procedure described in Tabatabai and Bremner (1969) or the fluorescent assay based on the release of 4-methylumbelliferone from 4-methylumbelliferonephosphate (MUP; Courty et al 2005Courty et al , 2006Pritsch et al 2004;Pritsch and Garbaye 2011) to estimate phosphomonoesterase activity.…”

Section: Introductionmentioning

confidence: 99%

Diversity in phosphorus mobilisation and uptake in ectomycorrhizal fungi

Plassard

Louche

Ali

et al. 2011

Abstract· Introduction Phosphorus (P) is often the first or second element limiting aboveground net primary productivity of forests. Besides low available inorganic orthophosphate (Pi) concentrations, soil may contain high total P contents, as insoluble mineral P or as organic P. Most plants form mycorrhizal associations that improve their P nutrition. Three main hypotheses have been proposed to explain this positive effect through an increase of (1) P mobilisation from mineral P, (2) P mobilisation from organic P and (3) soil exploration and P uptake. However, the positive effect of mycorrhizal symbiosis may be variable with the fungal species forming the association. This could be due to the different abilities of mycorrhizal fungi to mobilise P and/or to take up Pi from the soil.· Objectives The aim of this review was to examine our current knowledge about the capacity of ectomycorrhizal fungi to release organic compounds as low-molecularweight organic anions and phosphatases thought to have a role for mineral and organic P mobilisation, respectively. The diversity of Pi transporters among mycorrhizal species is also examined.· Results The main conclusion is that the study of the functional diversity of ectomycorrhizal fungi in situ is still a challenging question and could be addressed by combining different tools now available to make large-scale studies.